Is.456-2000
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About This Presentation
IS CODE
Slide Content
Disclosure to Promote the Right To Information
Whereas the Parliament of India has set out to provide a practical regime of right to
information for citizens to secure access to information under the control of public authorities,
in order to promote transparency and accountability in the working of every public authority,
and whereas the attached publication of the Bureau of Indian Standards is of particular interest
to the public, particularly disadvantaged communities and those engaged in the pursuit of
education and knowledge, the attached public safety standard is made available to promote the
timely dissemination of this information in an accurate manner to the public.
इंटरनेट मानक
“!ान $ एक न' भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
“Invent a New India Using Knowledge”
“प0रा1 को छोड न' 5 तरफ”
Jawaharlal Nehru
“Step Out From the Old to the New”
“जान1 का अ+धकार, जी1 का अ+धकार”
Mazdoor Kisan Shakti Sangathan
“The Right to Information, The Right to Live”
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”
“Invent a New India Using Knowledge”
है”ह”हIS 456 (2000): Plain and Reinforced Concrete - Code of
Practice [CED 2: Cement and Concrete]
Whereas the Parliament of India has set out to provide a practical regime of right to
information for citizens to secure access to information under the control of public authorities,
in order to promote transparency and accountability in the working of every public authority,
and whereas the attached publication of the Bureau of Indian Standards is of particular interest
to the public, particularly disadvantaged communities and those engaged in the pursuit of
education and knowledge, the attached public safety standard is made available to promote the
timely dissemination of this information in an accurate manner to the public.
इंटरनेट मानक
“!ान $ एक न' भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
“Invent a New India Using Knowledge”
“प0रा1 को छोड न' 5 तरफ”
Jawaharlal Nehru
“Step Out From the Old to the New”
“जान1 का अ+धकार, जी1 का अ+धकार”
Mazdoor Kisan Shakti Sangathan
“The Right to Information, The Right to Live”
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”
“Invent a New India Using Knowledge”
है”ह”हIS 456 (2000): Plain and Reinforced Concrete - Code of
Practice [CED 2: Cement and Concrete]
July 2000
IS.456 : 2000
( R••fflrmed2005 )
IndianStandard
PLAINANDREINFORCEDCONCRETE
CODEOFPRACTICE
(FourthRevision)
TenthReprintAPRIL2007
(IncludingAmendmentsNo. Iand2)
ICS91.100.30
CBI52000
BUREAU OFINDIANSTANDARDS
MANAKBHAVAN.9BAHADURSHAHZAFARMARG
NEWDELIiI110002
PriceRs.830.09+Rs.120.09
IS.456 : 2000
( R••fflrmed2005 )
IndianStandard
PLAINANDREINFORCEDCONCRETE
CODEOFPRACTICE
(FourthRevision)
TenthReprintAPRIL2007
(IncludingAmendmentsNo. Iand2)
ICS91.100.30
CBI52000
BUREAU OFINDIANSTANDARDS
MANAKBHAVAN.9BAHADURSHAHZAFARMARG
NEWDELIiI110002
PriceRs.830.09+Rs.120.09
IS456:2000
CONTENTS
PAGE
SECTION1GENERAL
JSCOPE
2REFERBNCES
3TERMINOLOGY
4SVMBOU
SECTION2MATERIALS,WORKMANSHIP,INSPECTIONANDTESTING
5MATERIALS
5.1Cement
5.2MineralAdmixtures
5.3Aggregates
5.4Water
5.5Admixtures
5.6Reinforcement
5.7 Storage of Materials
6
CONCRETE
6.1 Grades
6.2 Propertiesof Concrete
7WORKABIUTY OF CONCRETE
8DURABILITYOFCONCRETE
8.1General
8.2RequirementsforDurability
9
CONCRETEMIXPROPORTIONING
9.1 Mix Proportion
9.2 DesignMixConcrete
9.3 Nominal Mix Concrete
10PRODUlllONOF CONCRETE
10.1QualityAssuranceMeasures
10.2 Batching
10.3 Mixing
11FORMWORK
1J.1 General
11.2 Cleaning and
Treatmentof Fonnwork
11.3StrippingTime
12ASSEMBLYOFREINFORCEMENT
·13TRANSPORTING,PLACING,COMPACTION ANDCURING
J3.1 Transportingand Handling
13.2 Placing
13.3 Compaction
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CONTENTS
PAGE
SECTION1GENERAL
JSCOPE
2REFERBNCES
3TERMINOLOGY
4SVMBOU
SECTION2MATERIALS,WORKMANSHIP,INSPECTIONANDTESTING
5MATERIALS
5.1Cement
5.2MineralAdmixtures
5.3Aggregates
5.4Water
5.5Admixtures
5.6Reinforcement
5.7 Storage of Materials
6
CONCRETE
6.1 Grades
6.2 Propertiesof Concrete
7WORKABIUTY OF CONCRETE
8DURABILITYOFCONCRETE
8.1General
8.2RequirementsforDurability
9
CONCRETEMIXPROPORTIONING
9.1 Mix Proportion
9.2 DesignMixConcrete
9.3 Nominal Mix Concrete
10PRODUlllONOF CONCRETE
10.1QualityAssuranceMeasures
10.2 Batching
10.3 Mixing
11FORMWORK
1J.1 General
11.2 Cleaning and
Treatmentof Fonnwork
11.3StrippingTime
12ASSEMBLYOFREINFORCEMENT
·13TRANSPORTING,PLACING,COMPACTION ANDCURING
J3.1 Transportingand Handling
13.2 Placing
13.3 Compaction
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IS 456:ZOOO
13.4 ConstructionJoints and Cold Joints
13.5 Curing
13.6 Supervision
14CONCRETINGUNDERSPECIALCosornoss
14.1WorkinExtremeWeatherConditions
14.2Under-WaterConcreting
15SAMPLING ANDSTRENGTHOFDESIGNEDCONCRETEMIX
15.1General
15.2FrequencyofSampling
IS.3Test Specimen
15.4 Test Resultsof Sample
16ACCEPTANCE
CRITERIA
17INS"EcrlONANDTESTINGOFSTRUCTURE
SECTION3GENERALDESIGNCONSIDERATION
18BASESRlRDESIGN
18.1Aim ofDesign
18.2 Methods of Design
18.3Durability,Workmanshipand Materials
18.4 Design Process
19LOADSANDFORCES
t9.1 General
19.2 Dead Loads
19.3ImposedLoads,Wind Loads and Snow Loads
19.4
EarthquakeForces
19.5 Shrinkage,Creep andTemperatureEffects
19.6 Other Forces and Effects
J9.7 Combinationof Loads
19.8 Dead LoadCounteractingOther
Loadsand Forces
19.9DesignLoad
20STABILITYOF THE STRUC1lJRE
20.1Overturning
20.2 Sliding
20.3 ProbableVariation
inDead Load
20.4 MomentConnection
20.5
LateralSway
21FIRE
REsiSTANCE
22ANALYSIS
22.1 General
22.2 Effective Span
22.3 Stiffness
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3.5
13.4 ConstructionJoints and Cold Joints
13.5 Curing
13.6 Supervision
14CONCRETINGUNDERSPECIALCosornoss
14.1WorkinExtremeWeatherConditions
14.2Under-WaterConcreting
15SAMPLING ANDSTRENGTHOFDESIGNEDCONCRETEMIX
15.1General
15.2FrequencyofSampling
IS.3Test Specimen
15.4 Test Resultsof Sample
16ACCEPTANCE
CRITERIA
17INS"EcrlONANDTESTINGOFSTRUCTURE
SECTION3GENERALDESIGNCONSIDERATION
18BASESRlRDESIGN
18.1Aim ofDesign
18.2 Methods of Design
18.3Durability,Workmanshipand Materials
18.4 Design Process
19LOADSANDFORCES
t9.1 General
19.2 Dead Loads
19.3ImposedLoads,Wind Loads and Snow Loads
19.4
EarthquakeForces
19.5 Shrinkage,Creep andTemperatureEffects
19.6 Other Forces and Effects
J9.7 Combinationof Loads
19.8 Dead LoadCounteractingOther
Loadsand Forces
19.9DesignLoad
20STABILITYOF THE STRUC1lJRE
20.1Overturning
20.2 Sliding
20.3 ProbableVariation
inDead Load
20.4 MomentConnection
20.5
LateralSway
21FIRE
REsiSTANCE
22ANALYSIS
22.1 General
22.2 Effective Span
22.3 Stiffness
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3.5
22.4StructuralFrames
22.5MomentandShearCoefficientsfor
ContinuousBeams
22.6CriticalSections
forMomentandShear
22.7Redistribution
ofMoments
23BEAMS
23.0EffectiveDepth
23.1 T-Beams andL-Beams
23.2Control ofDeflection
23.3SlendernessLimits forBeamstoEnsureLateralStability
24SOLIDSLABS
24.1 General
24.2SlabsContinuous OverSupports
24.3SlabsMonolithicwithSupports
24.4
SlabsSpanningin TwoDirectionsatRight Angles
24.5LoadsonSupportingBeams
25COMPRESSION MEMBERS
25.1Definitions
25.2EffectiveLength
ofCompressionMembers
25.3Slenderness
LimitsforColumns
25.4 MinimumEccentricity
26REQUIREMENTS QOVERNING REINFORCEMENT AND DETAILING
26. IGeneral
26.2Development
ofStress in Reinforcement
26.3SpacingofReinforcement
26.4 NominalCoverto Reinforcement
26.5Requirements ofReinforcementforStructuralMembers
27
EXPANSION
JOINTS
SECTION4SPECIALDESIGNREQUIREMENTS FOR
STRUCTURAL MEMBERSANDSYSTEMS
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28CONCRETE CORBELS 51
28.1General 51
28.2Design 51
29DEEPBEAMS 51
29.1General 51
29.2Lever Arm SI
29.3Reinforcement 51
30RIBBED,HOLU)WBLOCKORVOlDEnSLAB 52
30.1General 52
30.2AnalysisofStructure 52
30.3Shear
52
30.4Deflection 52
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22.5MomentandShearCoefficientsfor
ContinuousBeams
22.6CriticalSections
forMomentandShear
22.7Redistribution
ofMoments
23BEAMS
23.0EffectiveDepth
23.1 T-Beams andL-Beams
23.2Control ofDeflection
23.3SlendernessLimits forBeamstoEnsureLateralStability
24SOLIDSLABS
24.1 General
24.2SlabsContinuous OverSupports
24.3SlabsMonolithicwithSupports
24.4
SlabsSpanningin TwoDirectionsatRight Angles
24.5LoadsonSupportingBeams
25COMPRESSION MEMBERS
25.1Definitions
25.2EffectiveLength
ofCompressionMembers
25.3Slenderness
LimitsforColumns
25.4 MinimumEccentricity
26REQUIREMENTS QOVERNING REINFORCEMENT AND DETAILING
26. IGeneral
26.2Development
ofStress in Reinforcement
26.3SpacingofReinforcement
26.4 NominalCoverto Reinforcement
26.5Requirements ofReinforcementforStructuralMembers
27
EXPANSION
JOINTS
SECTION4SPECIALDESIGNREQUIREMENTS FOR
STRUCTURAL MEMBERSANDSYSTEMS
IS456:2000
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28CONCRETE CORBELS 51
28.1General 51
28.2Design 51
29DEEPBEAMS 51
29.1General 51
29.2Lever Arm SI
29.3Reinforcement 51
30RIBBED,HOLU)WBLOCKORVOlDEnSLAB 52
30.1General 52
30.2AnalysisofStructure 52
30.3Shear
52
30.4Deflection 52
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30.5 Size and PositionofRibs
30.6 Hollow Blocks and Formers
30.7ArrangementofReinforcement
30.8 PrecastJoistsandHollowFillerBlocks
31FLATSLABS
33STAIRS
33.1 Effective SpanofStairs
33.2Distributionof Loadingon Stairs
33.3DepthofSection
34FOOT1NOS
34.JGeneral
34.2 MomentsandForces
34.3 Tensile Reinforcement
34.4 Transfer
ofLoadattheBase of Column34.5Nominal Reinforcement
31.1
31.2
31.3
31.431.5
31.6
31.7
31.8
32WAUS
32.1
32.2
32.3
32.432.S
General
Proportioning
Detenninationof Bendin. Moment
DirectDesipMethod
EquivalentFnmeMethod
Shear in Flat Slab
SlabReinforcement
Openingsin Flat Slabs
General
EmpiricalDesignMethodfor
Wall~SubjectedtoInplane VerticalLoads
WallsSubjectedto CombinedHorizontaland VerticalForces
DesignforHorizontalShear
MinimumRequirementsforReinforcementinWalls
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SECTION5STRUCTURALDESIGN(LIMITSTATEMETHOD)
3SSAFETYANDSERVICEAlIUI'YRsoUIREMBNTS
3S.1General
35.2 LimitStateof Collapse
35.3Limit StatesofServiceability
3S.4Other LimitStates
36CHARACTBRISTIC AND DEsIGNVALtmsANDPAR11AL SAFETYFACIORS
36.1Ch8rIcteristicStrenathofMaterials
36.2CharacteristicLoads
36.3DesipValues
36.4PartialSafetyFactors
37ANALYSIS
37.1AnalysisofStructure
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30.5 Size and PositionofRibs
30.6 Hollow Blocks and Formers
30.7ArrangementofReinforcement
30.8 PrecastJoistsandHollowFillerBlocks
31FLATSLABS
33STAIRS
33.1 Effective SpanofStairs
33.2Distributionof Loadingon Stairs
33.3DepthofSection
34FOOT1NOS
34.JGeneral
34.2 MomentsandForces
34.3 Tensile Reinforcement
34.4 Transfer
ofLoadattheBase of Column34.5Nominal Reinforcement
31.1
31.2
31.3
31.431.5
31.6
31.7
31.8
32WAUS
32.1
32.2
32.3
32.432.S
General
Proportioning
Detenninationof Bendin. Moment
DirectDesipMethod
EquivalentFnmeMethod
Shear in Flat Slab
SlabReinforcement
Openingsin Flat Slabs
General
EmpiricalDesignMethodfor
Wall~SubjectedtoInplane VerticalLoads
WallsSubjectedto CombinedHorizontaland VerticalForces
DesignforHorizontalShear
MinimumRequirementsforReinforcementinWalls
S2
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S3
S3
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S1
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SECTION5STRUCTURALDESIGN(LIMITSTATEMETHOD)
3SSAFETYANDSERVICEAlIUI'YRsoUIREMBNTS
3S.1General
35.2 LimitStateof Collapse
35.3Limit StatesofServiceability
3S.4Other LimitStates
36CHARACTBRISTIC AND DEsIGNVALtmsANDPAR11AL SAFETYFACIORS
36.1Ch8rIcteristicStrenathofMaterials
36.2CharacteristicLoads
36.3DesipValues
36.4PartialSafetyFactors
37ANALYSIS
37.1AnalysisofStructure
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38LIMITSTATBOPCOLLAPSE:FLEXURE
38.1A.lumptions
39LIMITSTATBOFCOUAPSS:COMPRESSION
39.1Assumptions
39.2 MinimumEccentricity
39.3 ShortAxiallyLoadedMembersinCompression
39.4CompressionMemberswithHelicalReinforcement
39.5MembenSubjectedtoCombinedAxialLoadandU~iaxial Bendins
39.6Memben SubjectedtoCombinedAxialLoadandBiaxialBending
39.7 SlenderCompressionMembers
40LlMrrSTATSOPCOLLAPSE:SHEAR
40.1 Nominal Shear Stress
40.2DesianShearStrensthofConcrete
40.3MinimumShearReinforcement
40.4DesiSDofShearReinforcement
4O.SBnhancedShearStrengthofSectionsClosetoSupports
41LIMrrSTATEOPCOLLAPSB:TORSION
41.1 General
41.2 Critical Section
41.3 Shear and
Torsion
41.4Reinforcement inMembersSubjected toTorsion
42LIMITSTATEOF
SBRVlCEABD.nY:DEFLECTION
42.1 FlexuralMembers
43LIMITSTATE OFSERVICEABILITY'CRACKING
43.1FlexuralMembers
43.2Compre~ion Members
ANNEXALIST OFREFERREDINDIANSTANDARDS
ANNEXBSTRUCTURALDESIGN(WORKINGSTRESSMETHOD)
B-1GENERAL
B-1.1 General Design Requirements
B-l.2Redistributionof Moments
B-l.3AssumptionsforDesignofMembers
B-2PBRMIsslBLBSTRESSBS
8-2.1PermissibleStressesin Concrete
8-2.2PermissibleStressesin SteelReinforcement
B-2.3 Increase in Permissible Stresses
B-3PBRMIssIBLELoADS INCOMPRBSSIONMEMBERS
B-3.1 Pedestals and Sbort ColumnswithLateral Ties
8-3.2ShonColumnswithHelicalReinforcement
B-3.3
Lon.Columns
8-3.4CompositeColumns
211e815/07-3
".
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38.1A.lumptions
39LIMITSTATBOFCOUAPSS:COMPRESSION
39.1Assumptions
39.2 MinimumEccentricity
39.3 ShortAxiallyLoadedMembersinCompression
39.4CompressionMemberswithHelicalReinforcement
39.5MembenSubjectedtoCombinedAxialLoadandU~iaxial Bendins
39.6Memben SubjectedtoCombinedAxialLoadandBiaxialBending
39.7 SlenderCompressionMembers
40LlMrrSTATSOPCOLLAPSE:SHEAR
40.1 Nominal Shear Stress
40.2DesianShearStrensthofConcrete
40.3MinimumShearReinforcement
40.4DesiSDofShearReinforcement
4O.SBnhancedShearStrengthofSectionsClosetoSupports
41LIMrrSTATEOPCOLLAPSB:TORSION
41.1 General
41.2 Critical Section
41.3 Shear and
Torsion
41.4Reinforcement inMembersSubjected toTorsion
42LIMITSTATEOF
SBRVlCEABD.nY:DEFLECTION
42.1 FlexuralMembers
43LIMITSTATE OFSERVICEABILITY'CRACKING
43.1FlexuralMembers
43.2Compre~ion Members
ANNEXALIST OFREFERREDINDIANSTANDARDS
ANNEXBSTRUCTURALDESIGN(WORKINGSTRESSMETHOD)
B-1GENERAL
B-1.1 General Design Requirements
B-l.2Redistributionof Moments
B-l.3AssumptionsforDesignofMembers
B-2PBRMIsslBLBSTRESSBS
8-2.1PermissibleStressesin Concrete
8-2.2PermissibleStressesin SteelReinforcement
B-2.3 Increase in Permissible Stresses
B-3PBRMIssIBLELoADS INCOMPRBSSIONMEMBERS
B-3.1 Pedestals and Sbort ColumnswithLateral Ties
8-3.2ShonColumnswithHelicalReinforcement
B-3.3
Lon.Columns
8-3.4CompositeColumns
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".
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B-4 MEMBBRSSUlJBCTIDTOCOMBINEDAxIALloADANDBINDING
8-4.1 De,iIDBaedonUncrackedSection
B-4.2DelilftBaedonCrackedSection
B-4.3MembersSubjectedto Combined DirectLoadandFlexure
D-S SHEAR
B-S,1NominalShearStress.
B-5,2neaipShearStrenlthofConcrete
B-S.3MinimumShearReinforcement
B-5.4 Desiln of ShearReinforcement
B·'.'EnhancedShearStrengthofSectionsClose to Supports
B-6 TORSION
B-6.1General
B-6.2 CriticalSection
B-6.3ShearandTorsion
B-6.4Reinforcement in Members Subjected to Torsion
ANNEXCCALCULATIONOFDEFLECTION
e-lTOTALD8PLIIcnON
C-2 SHOIlT-TBIMDBPLICTION
C-3 DBPLECI10NDuETOSHRINKAGE
C-4 DIFLECI10NDUETOCREEP
ANNEXDSLABSSPANNINGINTWODIRECTIONS
0·1IUmtAINIDSLAM
D-2SIM,tySuppotnSSUBS
ANNEXBSPPRCTIVILaNOTHOFCOLUMNS
ANNEXFCALCULAnONOFCRACKWID1lI
ANNEXGMOM!NTSOPltBSlSTANCBFORRECTANGULARANDT-SECI10NS
G-l RscrANOULAR SBC110NS
0-1.1Sections without ComprealionReinforcement
0-1.2SectionswithCompressionReinforcement
0-2FLANOEDSEC110N
ANNEXHCOMMITTEECOMPOSITION
10
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B-4 MEMBBRSSUlJBCTIDTOCOMBINEDAxIALloADANDBINDING
8-4.1 De,iIDBaedonUncrackedSection
B-4.2DelilftBaedonCrackedSection
B-4.3MembersSubjectedto Combined DirectLoadandFlexure
D-S SHEAR
B-S,1NominalShearStress.
B-5,2neaipShearStrenlthofConcrete
B-S.3MinimumShearReinforcement
B-5.4 Desiln of ShearReinforcement
B·'.'EnhancedShearStrengthofSectionsClose to Supports
B-6 TORSION
B-6.1General
B-6.2 CriticalSection
B-6.3ShearandTorsion
B-6.4Reinforcement in Members Subjected to Torsion
ANNEXCCALCULATIONOFDEFLECTION
e-lTOTALD8PLIIcnON
C-2 SHOIlT-TBIMDBPLICTION
C-3 DBPLECI10NDuETOSHRINKAGE
C-4 DIFLECI10NDUETOCREEP
ANNEXDSLABSSPANNINGINTWODIRECTIONS
0·1IUmtAINIDSLAM
D-2SIM,tySuppotnSSUBS
ANNEXBSPPRCTIVILaNOTHOFCOLUMNS
ANNEXFCALCULAnONOFCRACKWID1lI
ANNEXGMOM!NTSOPltBSlSTANCBFORRECTANGULARANDT-SECI10NS
G-l RscrANOULAR SBC110NS
0-1.1Sections without ComprealionReinforcement
0-1.2SectionswithCompressionReinforcement
0-2FLANOEDSEC110N
ANNEXHCOMMITTEECOMPOSITION
10
PAGI
83
83
83
83
83
83
84
8S
85
8S
86
86
86
86
86
88
88
88
88
89
90
90
90
92
95
96
96
96
96
96
98
AMENDMENT NO.IJUNI.1
TO
IS45'I2000PLAINANDREINFORCEDCONCIITI-CODIorPRACI'ICE
("owI"R,,,,,,,,,,)
(PIa'2,FONWOrd,,."bu'OII'II,.,)-Subltltute'Aa318:1995'fortAClII',i.'.
(PilI'1I,C/4UH~)-,DeletetII,maler'L.-HorllDntlldlltlDCI.&we..c.DtIIIoflateralllllnla,'.
(Pill'15.c/tllU.,.J.Till,)-Subltltute'CIa••lealAd_lxlu..'lor'Ad.IIt.....'.
.(Pal-17,clGUIf7.1)-SubltllUteIbefollowln,fortileexlaliDlIDfomalIIble:
•
Placlll'CDndlllt»u DI,,_o/ SIw¥
WorluJbUlly (11IIII)
(1) (2) (3)
BUDdinlconcrete;
}
Shallowaeetlonl; Verylow S.'.l.l
'avementaullnsplven
Ma..concrete;
Uptlyreinforced
ICctioDiinIJ.hi,
belma,willa,columna; Low 25-75
Floon;
Hindplacedpavements;
Canallining;
Stripfootings
Heavilyreinforced
}
sectionsinslabs, Medium 50-100
beams,walla,columna;
Slipformwork;
]
Medium 75·100
Pumpedconcrete
Trenchfi1l;
]
High 100·IS0
In-situpiling
Tremieconcrete Veryhigh See7.1.1
Nom-Formoatof...placiD.conditions,internalvilnlOIS(aeedlevibralorl) .resuitable.TIleeli.....fIl ..
determinedbaaed08thedensityandspaciDIofreinforcementbarsIDdthieD"ofIeCIioILFortlemi.~ va aN...
10beused(su.Lto113).
(Page19,Table4,columnS,,ub-heading)-Substitute'Free'for'Face'•
(Page27,claus«13.5.3) -Delete.
(PQge29,clause15.3):
a)Substitute'specimens' lor'samples'in lines 2,61nd7.
b)Substitute'IS9013'lor'IS9103' .
I.(Page29,clause1'.1) -Substitute 'conditions'for'condition' inline3 andtbefoJlowinl....uaforlilte~
:'matteragainst'I)':
'I)The meanstrengtbdeterminedfromanygroupofCournon-ovcriappiMcoftlCCUtivelal.-IIII'DIIPIIII_"
appropriatelimitsincolumn2 ofTable11.'
(Ptl,~29,claus«1'.3,par«2 ) - Substitute'col3tlor'col 2' .
(Page29,clalUe1'.4,line2 ) -SubstituteC16.1or16.2asthecasemaybe'lor'1'.3-.
:.(Ptl,~30,TableII,colum"3 ) - Substitute'~Ick-3'lor'aIe..-3,Inda_I.."II4t,or'.!........
;~.
,oj
,:~~·Prlc.Greup3 1
TO
IS45'I2000PLAINANDREINFORCEDCONCIITI-CODIorPRACI'ICE
("owI"R,,,,,,,,,,)
(PIa'2,FONWOrd,,."bu'OII'II,.,)-Subltltute'Aa318:1995'fortAClII',i.'.
(PilI'1I,C/4UH~)-,DeletetII,maler'L.-HorllDntlldlltlDCI.&we..c.DtIIIoflateralllllnla,'.
(Pill'15.c/tllU.,.J.Till,)-Subltltute'CIa••lealAd_lxlu..'lor'Ad.IIt.....'.
.(Pal-17,clGUIf7.1)-SubltllUteIbefollowln,fortileexlaliDlIDfomalIIble:
•
Placlll'CDndlllt»u DI,,_o/ SIw¥
WorluJbUlly (11IIII)
(1) (2) (3)
BUDdinlconcrete;
}
Shallowaeetlonl; Verylow S.'.l.l
'avementaullnsplven
Ma..concrete;
Uptlyreinforced
ICctioDiinIJ.hi,
belma,willa,columna; Low 25-75
Floon;
Hindplacedpavements;
Canallining;
Stripfootings
Heavilyreinforced
}
sectionsinslabs, Medium 50-100
beams,walla,columna;
Slipformwork;
]
Medium 75·100
Pumpedconcrete
Trenchfi1l;
]
High 100·IS0
In-situpiling
Tremieconcrete Veryhigh See7.1.1
Nom-Formoatof...placiD.conditions,internalvilnlOIS(aeedlevibralorl) .resuitable.TIleeli.....fIl ..
determinedbaaed08thedensityandspaciDIofreinforcementbarsIDdthieD"ofIeCIioILFortlemi.~ va aN...
10beused(su.Lto113).
(Page19,Table4,columnS,,ub-heading)-Substitute'Free'for'Face'•
(Page27,claus«13.5.3) -Delete.
(PQge29,clause15.3):
a)Substitute'specimens' lor'samples'in lines 2,61nd7.
b)Substitute'IS9013'lor'IS9103' .
I.(Page29,clause1'.1) -Substitute 'conditions'for'condition' inline3 andtbefoJlowinl....uaforlilte~
:'matteragainst'I)':
'I)The meanstrengtbdeterminedfromanygroupofCournon-ovcriappiMcoftlCCUtivelal.-IIII'DIIPIIII_"
appropriatelimitsincolumn2 ofTable11.'
(Ptl,~29,claus«1'.3,par«2 ) - Substitute'col3tlor'col 2' .
(Page29,clalUe1'.4,line2 ) -SubstituteC16.1or16.2asthecasemaybe'lor'1'.3-.
:.(Ptl,~30,TableII,colum"3 ) - Substitute'~Ick-3'lor'aIe..-3,Inda_I.."II4t,or'.!........
;~.
,oj
,:~~·Prlc.Greup3 1
AmendNo.1 to IS456:2000
(Page33,clause21.3,line2 )Hll>stIMUlcticlt'f~'section'.
[Page37,clause23.:.2~6-:-~bstilUte'b'-'O~ ~~lo'lor'1
0
'.'b'lor'b'and'b:lor'b:intheformulae.
( Page46,clauseZ6.4!"-~bstil:F¥.\3rfor 8.2.3'.
I.
lPage49,clause26.5.3.1(c)(2),lasIline]- Substitute'6mm'for'16mm'.
(Page62,clause3%.Z.5) -~ubstitute 'H;"for'H
w e
'in theexplanationof e._
(Page62,clause3%.3.1,line4 ) - Substitute'32.4'lor'32.3'.
[Page62,clause3%.4.3(b),line6 ] -Insert'"few'betweenthewords'but' and 'shall'.
[Page65,clause34.%.4.1(1),lastline]-InsertthefoJlowingafterthewords'depth of footing' :
'in caseof
footingson soils,andItadistanceequalto halftheeffectivedeptbof footing',
(Page68,Table18,col4 ) -Substitute,_, for'1.0'againsttbeLoadCombinationDL+ll:
(Page72,clause40.1 ) -Substitute'bd' for'b
d
'
in theformula.
(Page83,clauseB-4.J,line2 ) -Deletetheword'and' .
(Page85,clauseB.5.5.1,para2,
line6)- Substitute 'Table 24'for'Table23'.
(Page85,clauseB-5.5.%)-Substitutethe followingfortbeexistingformula:
'A.=Q)(T.
y-2dT.eIQ
y
)l«;~0.4Qyb/0.87/., ,
(Page90,clause»-1.11,line1 ) -Substitute'Where'lor'Torsion'.
(Page93,Fig.27 ) -Substitute''efl''for'IlL'.
( Page95,AnnexF ):
a) The referencetoFig. 28 given in column 1 of tbe text along witb the explanationoCtbesymbolsused intheFig,
28giventhereaftermaybereadjustbeforetbeformulagivenfortherectangulartensionzone..
b)Substitute 'compression'for'campression' intbeexplanationofsymbol'a'.
(Pages98to100,AnnexH)- Substitute the followingfor the existingAnnex:
IrriptiOlllndPowerReIellCIaInstitute.Amri...,
B. G.ShirkeConstructionTeQROlolYLid,Pune
HindusranPreCabLimited,NewDelhi
CentralPuhlicWorksDepartment,NewDelhi
S.rdarSarovlrNarmadaNipmLad,Oandhilllir
ANNEX H
(ForeM'ord)
COMMfITEECOMI)OSITION
CementandConcreteSectional Committee,CEO2
CluJi,,,.,,"
DRtl.C.VDVESVARAYA
·Ch.ndrib·,a'15·Cross,63-64EastParkRoad,
MalleswaralD,Banplore-S60003
~eprUQI/in,
OCLIndiaLtd,NewDelhi
DirectorateGeneralofSuppliesandDisposals.NewDelhi
MeIJtbe,.f
DaS. C.AHWWAUA
SHRIV.BAIASl/BRAMANlAN
StiliR. P.SlNOH (Alle'lIDt~)
SHRIG.R.BHAIUTKAR
SHRJA.K.CHADHA
SHJUJ.R.SIL(Al'erlUlle). ~
CmspENOINEBR(DfSlGN)
SUPI!IUNTBNDINOF.,NOINBa(S&,S) (Alte'lUJle)
CHIS'ENoINEBR(NAVOAMDAM)
SUPElUNl'ENDINOENaINEER(OCC)(Alter.'e)
CHIEFENGINEER(R!sfAICH}CUM..Dlitscroa
REsEARCHOffICER(CONCREl!TecIINOUXiY)
(A/terM/e)
2
(CDIII~CNI""3)
(Page33,clause21.3,line2 )Hll>stIMUlcticlt'f~'section'.
[Page37,clause23.:.2~6-:-~bstilUte'b'-'O~ ~~lo'lor'1
0
'.'b'lor'b'and'b:lor'b:intheformulae.
( Page46,clauseZ6.4!"-~bstil:F¥.\3rfor 8.2.3'.
I.
lPage49,clause26.5.3.1(c)(2),lasIline]- Substitute'6mm'for'16mm'.
(Page62,clause3%.Z.5) -~ubstitute 'H;"for'H
w e
'in theexplanationof e._
(Page62,clause3%.3.1,line4 ) - Substitute'32.4'lor'32.3'.
[Page62,clause3%.4.3(b),line6 ] -Insert'"few'betweenthewords'but' and 'shall'.
[Page65,clause34.%.4.1(1),lastline]-InsertthefoJlowingafterthewords'depth of footing' :
'in caseof
footingson soils,andItadistanceequalto halftheeffectivedeptbof footing',
(Page68,Table18,col4 ) -Substitute,_, for'1.0'againsttbeLoadCombinationDL+ll:
(Page72,clause40.1 ) -Substitute'bd' for'b
d
'
in theformula.
(Page83,clauseB-4.J,line2 ) -Deletetheword'and' .
(Page85,clauseB.5.5.1,para2,
line6)- Substitute 'Table 24'for'Table23'.
(Page85,clauseB-5.5.%)-Substitutethe followingfortbeexistingformula:
'A.=Q)(T.
y-2dT.eIQ
y
)l«;~0.4Qyb/0.87/., ,
(Page90,clause»-1.11,line1 ) -Substitute'Where'lor'Torsion'.
(Page93,Fig.27 ) -Substitute''efl''for'IlL'.
( Page95,AnnexF ):
a) The referencetoFig. 28 given in column 1 of tbe text along witb the explanationoCtbesymbolsused intheFig,
28giventhereaftermaybereadjustbeforetbeformulagivenfortherectangulartensionzone..
b)Substitute 'compression'for'campression' intbeexplanationofsymbol'a'.
(Pages98to100,AnnexH)- Substitute the followingfor the existingAnnex:
IrriptiOlllndPowerReIellCIaInstitute.Amri...,
B. G.ShirkeConstructionTeQROlolYLid,Pune
HindusranPreCabLimited,NewDelhi
CentralPuhlicWorksDepartment,NewDelhi
S.rdarSarovlrNarmadaNipmLad,Oandhilllir
ANNEX H
(ForeM'ord)
COMMfITEECOMI)OSITION
CementandConcreteSectional Committee,CEO2
CluJi,,,.,,"
DRtl.C.VDVESVARAYA
·Ch.ndrib·,a'15·Cross,63-64EastParkRoad,
MalleswaralD,Banplore-S60003
~eprUQI/in,
OCLIndiaLtd,NewDelhi
DirectorateGeneralofSuppliesandDisposals.NewDelhi
MeIJtbe,.f
DaS. C.AHWWAUA
SHRIV.BAIASl/BRAMANlAN
StiliR. P.SlNOH (Alle'lIDt~)
SHRIG.R.BHAIUTKAR
SHRJA.K.CHADHA
SHJUJ.R.SIL(Al'erlUlle). ~
CmspENOINEBR(DfSlGN)
SUPI!IUNTBNDINOF.,NOINBa(S&,S) (Alte'lUJle)
CHIS'ENoINEBR(NAVOAMDAM)
SUPElUNl'ENDINOENaINEER(OCC)(Alter.'e)
CHIEFENGINEER(R!sfAICH}CUM..Dlitscroa
REsEARCHOffICER(CONCREl!TecIINOUXiY)
(A/terM/e)
2
(CDIII~CNI""3)
( Coll,imuulfrom pa,e2 )
Memben
SHIllJ.P.DesAi
SURIB.K.JAGEnA(A/ierMle)
DlllEClOa
JOINT
DnucroR""'muJte)
DIRf.C1OIl(OdOD)(N&
W)
DPJVIYDIRlCIOR(CMDD)(NW&S)(A/tOlUJle)
SHRIK.H.OANGWAL
StWV.PA1TABHI(Allemtlle)
SHRIV.Ie.GHANBKAIl
SHRIS.GoPINA11I
SHRIR.TAM1lAJCAJlAN (Allenult~)
SHIUS.K.GuttATHAKURTA
SHIUS.SANKARANARAYANAN (Alternate)
SUIlIN.S.BUAL
DRIRsHADMASOOD(AltulIQle)
PRoPAK.JAIN
SHRJN.C.JAIN
JOINT
DlRBCTOR(STANDARDS)(B&S)(Cn..1)
JOINTDIIlPLiOR(STANDAaDS) (B&S)
(CB-II)
(Altenulte)
SHIUN.G.JOSID
SHRIP.D.KEUCAR(AIleJ'MIe)
SHRID.ItKANUNOO
SHuB.R.MBENA(Alterll4le)
SHRJP.KJusilNAMUanlY
StiliS.CHoWOIWRY(AltulUlte)
DRAG.MADHAVARAo
SIWK.MAN!(AltnlUlle)
SHIUJ.SAitUP
SHRIV.Sl1RmH
StiliD.P.SINOH(AltmuJle)
SHRJPRAFFuI.AKUMAR
SHRIP.P.NAIR(A11el7Ulk)
MBMBERSHCRETARY
DlllOCTOk(C'ML)(AlterlMle)
SHRIS.K.NAnHANI
DRAS.GOBI..(Alterll4.)
SHRJS.S.SEmIRA
SHRISATANDERKUMAR(AltOIUlIe)
SHRIY.R.PHLU
StlRlA.KSHARMA(AltG"rUIte)
DRC.IWKUMAR
DRK.MOHAN(Altemtllc)
SHRIS.ARBooI
REPRmIKl'A11W
SHIIJ.S.SANOANEIUA
SHIlLN.AnARWAL(AllemGle)
Sl1PBRIN1BmINGENOINI'JIl(DfSION)
ExID/l'M!ENoINm!.a(SMRDIVISION)(A/temale)
SHIUIe.K..TAPAIUA
SHIllA.Ie.JAIN(AI'......te)
SHRIT.H"TIwARI
ORD.GlaH(AlIe",,'e)
DRK.VINCATAaIALAN
SHRIN.CHANDIlASIICAlAN(AI'.....Ic)
Amend No.1toIS456:2000
RepresenJing
GujaraaAmbuja CementsLid,Ahmedabad
AP.EngineeringResearchLahoralOries,Hyderabad
CenlralWaterCommission,NewDelhi
HyderabadIndustrieslzd,Hyderabad
.r.
SaNemrslEngineering-It~r("h Centre(CSIR),Gha7jabad
TheIndiaCemenlSLJd.Chennai
GannonDunkerleyandCompany.lAd,Mumbai
CentralBuildingResearchInstitute(CSIR),Roorkee
UniversityofRoorkee,Roorkee
CementCorporationofIndiaLtd,NewDelhi
Research,Designs&.StandardsOrganization(MinistryorRailways).Lucknow
TheIndianHumePipeCompanyLad,Mumbai
NationalTestJlouse,Calculla
Larsen&.Tuhro1.Jd,Mumhai
StructuralEngineeringResearchCentre(CSIR),Chennai
HospitalServicesConsultancyCorporation(Iodia)lid,NewDelhi
HousingandUrbanDevelopmentCorporationlJd,NewDelhi
MinistryofSurfaceTransport.DepartmentofSurfaceTransport(Roads Win&),NewDelhi
CentralBoardofIrrigation&Power,NewDelhi
Engineer-In-Chlef'sBranch.ArmyHeadquarters,NewDelhi
CentralRoadResearchInstitute(eJIR),NewDelhi
IndianRoadsCongress.NewDelhi
NationalCouncilforCementandBuildineMaterials,BalJabprb
GammonIndialid.Mumbai
Builder'sAssociationofIndia,Mumbai
GeologicalSurveyofIndia.Calcutta
PuNicWorksDepanment.OovemmeDIorTamilNadu,Cbennai
IndianRayonandIndustriesI.Jd,Puoe
TheAssociatedCementCompanies l.Jd.Mumbai
CentralSoil.ndMaterialsResearchStatiOft,NewDelhi
3
(Continuel011POse..)
Memben
SHIllJ.P.DesAi
SURIB.K.JAGEnA(A/ierMle)
DlllEClOa
JOINT
DnucroR""'muJte)
DIRf.C1OIl(OdOD)(N&
W)
DPJVIYDIRlCIOR(CMDD)(NW&S)(A/tOlUJle)
SHRIK.H.OANGWAL
StWV.PA1TABHI(Allemtlle)
SHRIV.Ie.GHANBKAIl
SHRIS.GoPINA11I
SHRIR.TAM1lAJCAJlAN (Allenult~)
SHIUS.K.GuttATHAKURTA
SHIUS.SANKARANARAYANAN (Alternate)
SUIlIN.S.BUAL
DRIRsHADMASOOD(AltulIQle)
PRoPAK.JAIN
SHRJN.C.JAIN
JOINT
DlRBCTOR(STANDARDS)(B&S)(Cn..1)
JOINTDIIlPLiOR(STANDAaDS) (B&S)
(CB-II)
(Altenulte)
SHIUN.G.JOSID
SHRIP.D.KEUCAR(AIleJ'MIe)
SHRID.ItKANUNOO
SHuB.R.MBENA(Alterll4le)
SHRJP.KJusilNAMUanlY
StiliS.CHoWOIWRY(AltulUlte)
DRAG.MADHAVARAo
SIWK.MAN!(AltnlUlle)
SHIUJ.SAitUP
SHRIV.Sl1RmH
StiliD.P.SINOH(AltmuJle)
SHRJPRAFFuI.AKUMAR
SHRIP.P.NAIR(A11el7Ulk)
MBMBERSHCRETARY
DlllOCTOk(C'ML)(AlterlMle)
SHRIS.K.NAnHANI
DRAS.GOBI..(Alterll4.)
SHRJS.S.SEmIRA
SHRISATANDERKUMAR(AltOIUlIe)
SHRIY.R.PHLU
StlRlA.KSHARMA(AltG"rUIte)
DRC.IWKUMAR
DRK.MOHAN(Altemtllc)
SHRIS.ARBooI
REPRmIKl'A11W
SHIIJ.S.SANOANEIUA
SHIlLN.AnARWAL(AllemGle)
Sl1PBRIN1BmINGENOINI'JIl(DfSION)
ExID/l'M!ENoINm!.a(SMRDIVISION)(A/temale)
SHIUIe.K..TAPAIUA
SHIllA.Ie.JAIN(AI'......te)
SHRIT.H"TIwARI
ORD.GlaH(AlIe",,'e)
DRK.VINCATAaIALAN
SHRIN.CHANDIlASIICAlAN(AI'.....Ic)
Amend No.1toIS456:2000
RepresenJing
GujaraaAmbuja CementsLid,Ahmedabad
AP.EngineeringResearchLahoralOries,Hyderabad
CenlralWaterCommission,NewDelhi
HyderabadIndustrieslzd,Hyderabad
.r.
SaNemrslEngineering-It~r("h Centre(CSIR),Gha7jabad
TheIndiaCemenlSLJd.Chennai
GannonDunkerleyandCompany.lAd,Mumbai
CentralBuildingResearchInstitute(CSIR),Roorkee
UniversityofRoorkee,Roorkee
CementCorporationofIndiaLtd,NewDelhi
Research,Designs&.StandardsOrganization(MinistryorRailways).Lucknow
TheIndianHumePipeCompanyLad,Mumbai
NationalTestJlouse,Calculla
Larsen&.Tuhro1.Jd,Mumhai
StructuralEngineeringResearchCentre(CSIR),Chennai
HospitalServicesConsultancyCorporation(Iodia)lid,NewDelhi
HousingandUrbanDevelopmentCorporationlJd,NewDelhi
MinistryofSurfaceTransport.DepartmentofSurfaceTransport(Roads Win&),NewDelhi
CentralBoardofIrrigation&Power,NewDelhi
Engineer-In-Chlef'sBranch.ArmyHeadquarters,NewDelhi
CentralRoadResearchInstitute(eJIR),NewDelhi
IndianRoadsCongress.NewDelhi
NationalCouncilforCementandBuildineMaterials,BalJabprb
GammonIndialid.Mumbai
Builder'sAssociationofIndia,Mumbai
GeologicalSurveyofIndia.Calcutta
PuNicWorksDepanment.OovemmeDIorTamilNadu,Cbennai
IndianRayonandIndustriesI.Jd,Puoe
TheAssociatedCementCompanies l.Jd.Mumbai
CentralSoil.ndMaterialsResearchStatiOft,NewDelhi
3
(Continuel011POse..)
Ant.ndNo.1&0IS4_I2000
(COIIIiIlMM""""JJ
AI.....
DaH.e.V.~AJAYA
SHIID.C.CM1\JMDI(A~"")
StWYINODKuMAa
0111010'(elYBag)
SHRIC.R.AuMCHANDANI
SHRII.RANaAIWAN(AII.rlllll.)
DaP.C.OiowDHURY
OaC.S.VISHWANA11IA(A't.'IIII'.)
SHRll.·P.DIBAI
SHKiB.ItJAOBTIA(Alte,,,.,.)
DIRSC10R
SHRIN.OwmIWBlCAIAN(A"erute)
DUUICIOa(CANDO)
DBPUTYDIUC10I(CANDD)(AI,.",.,-)
JOINTDIIBC10RSTANDAIlDICB.lS)CB-1I
JOINTDIIBC1015TANDAaDS(BAs)ICB-r
(AIt.,,,,,,.)
SUPERINTI!NDINOENaMElcDJ!SIONS)
Ex!cUl1VlENGINeeR(DBIIONS)-111(Aile,.".'.)
SHRIV.K.OHANEKAR
SHRID.S.PRAKASHRAo(AI,.,,",,e)
SHaiS.Ie.OUHAl'IwaJaTA
SHRIS.P.SANICAIANARAYANAN(AllerMte)
StDUJ.S.~~
SHRILItJAIN
SHRIM.P.JABINOH
DRB.KAMBSWAIlARAo(Aller".,e)
CHIUENoINURAJOINTSECRBTAILY
SUPI'JlIN1'DIDINOENoINBBR(AI'.....")
PIIoPS.Ka.1IMAMool11lY
SHIUK.K.NAvAIl(Altc,.,..te)
DaS.C.MArn
MANAOINGDIUCTOI
S...M.KUNDU(AI,.".,.)
Stili S.K.NAn1tANI
LT-COLIe.S.CHAaAK(A'''''''')
SHRIB.V.B.PAl
S...M.G.DANDvA'n(AI.......)
SNRIA.B.PHADa
S...D.M.SAvua(AI,.",.,.)
SHRIY.R.PHuu.
S...S.S.S.1iIA(A''''''''''I)
SHIISATANDIIKUMAI(Al,.,.tcll)
If"""'",
'I\IlMdlutlolorBnaI--(lDdI.~Callull
DIrtcIo,0.1....1.81S(I:M-oIJtc1tJ",....)
M..".,.",.ti•
•taUI.Ie.PI.AMD
Addition..DlrtOIOr(elvBla).,.,
I'IIIIAMIAYPANT
Depu~PtrNlOr(Ov__•811
ConcreteIUbcq",mlne"CEO2:3
It.,..".",
NadonalCounciltorClm.DllndBulldin.MI••rlall,BaU."'"
IhlpConaullintlLId,Mumbal
TorsteelROlelrchPoundalloaInIndia,Calcutta
OujlnlAmbujaCemenllLad,Ahmedabad
Celli'llSoliIDdMlteria.ae..ucb5lado..NewDeihl
CeaenlWlterCommiuion.NewDelbi
Re_reb.DeliJIIIudSliDell"O'alnizatioD(MlDistryofRailwayl).lJacbow
CentralPublicWorbDepartment.NewDelhi
StructuralEneineerinaResearchCeDtre(CSIR).Ohazilbad
GannonDunkerleyandCoLad.MWDbai
AssociatedConsultinaServices.Mumbai
InpenoDiIcapacity
CenlralBuildincRCleirchInsdlUle(CSIR),Roorbe
PublicWorks[)e.-rament,Mumbai
lodi..IOlbtUIeofTechaololY.NowDelhi
NadoDalCouldl forCe"••'I.dBuildiD,Materiala.Ballabprla
Mild.-taDPrefabUlDileCl.NewDelhi
neAuociIIedc...a'CompilitllJd.Mum'"
n.HiDdUltllCoIIINCdolColJd.M.....I
Cea....1RoadReIeIrchIDlIiIUIe(CSIR).NewDellai
4
(C~_".,.5)
(COIIIiIlMM""""JJ
AI.....
DaH.e.V.~AJAYA
SHIID.C.CM1\JMDI(A~"")
StWYINODKuMAa
0111010'(elYBag)
SHRIC.R.AuMCHANDANI
SHRII.RANaAIWAN(AII.rlllll.)
DaP.C.OiowDHURY
OaC.S.VISHWANA11IA(A't.'IIII'.)
SHRll.·P.DIBAI
SHKiB.ItJAOBTIA(Alte,,,.,.)
DIRSC10R
SHRIN.OwmIWBlCAIAN(A"erute)
DUUICIOa(CANDO)
DBPUTYDIUC10I(CANDD)(AI,.",.,-)
JOINTDIIBC10RSTANDAIlDICB.lS)CB-1I
JOINTDIIBC1015TANDAaDS(BAs)ICB-r
(AIt.,,,,,,.)
SUPERINTI!NDINOENaMElcDJ!SIONS)
Ex!cUl1VlENGINeeR(DBIIONS)-111(Aile,.".'.)
SHRIV.K.OHANEKAR
SHRID.S.PRAKASHRAo(AI,.,,",,e)
SHaiS.Ie.OUHAl'IwaJaTA
SHRIS.P.SANICAIANARAYANAN(AllerMte)
StDUJ.S.~~
SHRILItJAIN
SHRIM.P.JABINOH
DRB.KAMBSWAIlARAo(Aller".,e)
CHIUENoINURAJOINTSECRBTAILY
SUPI'JlIN1'DIDINOENoINBBR(AI'.....")
PIIoPS.Ka.1IMAMool11lY
SHIUK.K.NAvAIl(Altc,.,..te)
DaS.C.MArn
MANAOINGDIUCTOI
S...M.KUNDU(AI,.".,.)
Stili S.K.NAn1tANI
LT-COLIe.S.CHAaAK(A'''''''')
SHRIB.V.B.PAl
S...M.G.DANDvA'n(AI.......)
SNRIA.B.PHADa
S...D.M.SAvua(AI,.",.,.)
SHRIY.R.PHuu.
S...S.S.S.1iIA(A''''''''''I)
SHIISATANDIIKUMAI(Al,.,.tcll)
If"""'",
'I\IlMdlutlolorBnaI--(lDdI.~Callull
DIrtcIo,0.1....1.81S(I:M-oIJtc1tJ",....)
M..".,.",.ti•
•taUI.Ie.PI.AMD
Addition..DlrtOIOr(elvBla).,.,
I'IIIIAMIAYPANT
Depu~PtrNlOr(Ov__•811
ConcreteIUbcq",mlne"CEO2:3
It.,..".",
NadonalCounciltorClm.DllndBulldin.MI••rlall,BaU."'"
IhlpConaullintlLId,Mumbal
TorsteelROlelrchPoundalloaInIndia,Calcutta
OujlnlAmbujaCemenllLad,Ahmedabad
Celli'llSoliIDdMlteria.ae..ucb5lado..NewDeihl
CeaenlWlterCommiuion.NewDelbi
Re_reb.DeliJIIIudSliDell"O'alnizatioD(MlDistryofRailwayl).lJacbow
CentralPublicWorbDepartment.NewDelhi
StructuralEneineerinaResearchCeDtre(CSIR).Ohazilbad
GannonDunkerleyandCoLad.MWDbai
AssociatedConsultinaServices.Mumbai
InpenoDiIcapacity
CenlralBuildincRCleirchInsdlUle(CSIR),Roorbe
PublicWorks[)e.-rament,Mumbai
lodi..IOlbtUIeofTechaololY.NowDelhi
NadoDalCouldl forCe"••'I.dBuildiD,Materiala.Ballabprla
Mild.-taDPrefabUlDileCl.NewDelhi
neAuociIIedc...a'CompilitllJd.Mum'"
n.HiDdUltllCoIIINCdolColJd.M.....I
Cea....1RoadReIeIrchIDlIiIUIe(CSIR).NewDellai
4
(C~_".,.5)
(c.,;,.".".".,.,...)
/;I...."
SMIIA.I.PwADRAo
SHUK.MANI(AI,.".,")
IHI.JC.LPima
SHIll.R.OA...IL(A',."....)
1...8.D.lAHAucal
StiliU.S.P.VIlMA~/"""")
SHII~RAo
StiliG.RAMAICI.HMANCAl'.",.")
SHIll.A.RIDD.
DaN.JC.NAVAl(AI,.,,...)
SHRII.C.SAWHNIY
SHI.R.P.MIHIOTIACAl"",.")
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SHiIN.K.SINHA
SHIIB.T.UNWAUA
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DRA.K.MnTAL
SHRIS.A.RsoDI
DRV.THlRlNBNODAM
DRC.IWKUMAR
S"IUS.A.REDol
(CED2)
AmendNo.1toIS45':2000
If."....,;".
Structural&aln••rinlReMarchC.nIN(CSIR),Chona.'
N.tlonalBulldift'ConltructlonCorponlionLad.NewDelhi
NuclearPowerCorporation,MUlllbai
A.P.En,I'''''''1ReaearchLabonlOrica,Hydenbad
GammolIndiaLId.Mumbai
anainOl,.IndiaIJd.NewDelhi
IDdianConcroleIn'lhule,Chonnll
MinlaaryorSurfaceTraftlporl(Road.Wina),NewDelhi
Inpenonalcapacity
PanelforRevisionorIS456,CEO2:2IP
RepNlCnl;lt,
NationalCouncilforCementandBuildin.Material.,aaUabprh
NationalCouncilforComenlandDulldln,Malerials,BaUabaarb
StructuralEnaineerinlRete.reh Centre(CSIR),Ohazilbad
UniversityofRoorkee,Roorke.,
InperlOnalcapacity
Centr.1PublicWorlclDepartment,NewDeihl
NallonalCoundlforCemcnllndDuildin. Material.,BlUablarh
CentralPublicWorklDepartment,NewDeIhl
GAmmonIndiaLcd,Mumbai
SchoolofPlanninaandArchitecture,NewDelhi
SpecialAd-HocGroupforRevisionof IS456
Convener
DRH.C.VISVP.5VAItAVA
'Chandrika',II15
d1
Cross.63-64BasIParkRoad,
Malleswaram.Banaalore..S60003
NationalCouncilrorCementandSuildinaMaterials,Ballabearb
GammonIndiaLJd,Murnbai
5
/;I...."
SMIIA.I.PwADRAo
SHUK.MANI(AI,.".,")
IHI.JC.LPima
SHIll.R.OA...IL(A',."....)
1...8.D.lAHAucal
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SHII~RAo
StiliG.RAMAICI.HMANCAl'.",.")
SHIll.A.RIDD.
DaN.JC.NAVAl(AI,.,,...)
SHRII.C.SAWHNIY
SHI.R.P.MIHIOTIACAl"",.")
Pao,M.S.SHIm'
SHiIN.K.SINHA
SHIIB.T.UNWAUA
AI.,.,..,
01ANlLKUMAR
SURIV.K.OtlANBlCAR
Paa.AItJAIN
SHIILK.JAIN
StlRIJOI!KURIAN
DaS.C.MAm
DRA.K.MnTAL
SHRIS.A.RsoDI
DRV.THlRlNBNODAM
DRC.IWKUMAR
S"IUS.A.REDol
(CED2)
AmendNo.1toIS45':2000
If."....,;".
Structural&aln••rinlReMarchC.nIN(CSIR),Chona.'
N.tlonalBulldift'ConltructlonCorponlionLad.NewDelhi
NuclearPowerCorporation,MUlllbai
A.P.En,I'''''''1ReaearchLabonlOrica,Hydenbad
GammolIndiaLId.Mumbai
anainOl,.IndiaIJd.NewDelhi
IDdianConcroleIn'lhule,Chonnll
MinlaaryorSurfaceTraftlporl(Road.Wina),NewDelhi
Inpenonalcapacity
PanelforRevisionorIS456,CEO2:2IP
RepNlCnl;lt,
NationalCouncilforCementandBuildin.Material.,aaUabprh
NationalCouncilforComenlandDulldln,Malerials,BaUabaarb
StructuralEnaineerinlRete.reh Centre(CSIR),Ohazilbad
UniversityofRoorkee,Roorke.,
InperlOnalcapacity
Centr.1PublicWorlclDepartment,NewDeihl
NallonalCoundlforCemcnllndDuildin. Material.,BlUablarh
CentralPublicWorklDepartment,NewDeIhl
GAmmonIndiaLcd,Mumbai
SchoolofPlanninaandArchitecture,NewDelhi
SpecialAd-HocGroupforRevisionof IS456
Convener
DRH.C.VISVP.5VAItAVA
'Chandrika',II15
d1
Cross.63-64BasIParkRoad,
Malleswaram.Banaalore..S60003
NationalCouncilrorCementandSuildinaMaterials,Ballabearb
GammonIndiaLJd,Murnbai
5
II..•AMENDMENT NO. 2SE'riMBER 2~Or
TO ~.
tW\U'"
IS456:2000PLAI.NANDREINFO~D CONCRETE-
CODEOF'PRACTICE
( FIJUrthRevision),
( Page13,clause5.2.1.1,line1 ) -Substitute'IS 3812 (Part1)'for
'Graderens3812'.
( Page13,clause5.2.1.2andcorrespondingNote) - Substitutethe
followingfortheexisting:
..Silicafumeconformingto IS15388maybeusedas partreplacementofcement
provideduniformblendingwiththecementisensured.
NOTE- Silica fume isusuallyusedin proportionof~to 10 percent of the cement
content of a mix.'
tPage
13.Noteunderclause5.2.1.3,line5 ) -Substitute'be'for'range
frombeing'!.
( Page25..clause10.3.3,line4 )- Deletethe word 'and'.
(Page65.clause34.2.4.2.line1 )-Substitute'on' for'or'.
[Page65.clause34.3.1(a)..line2I -Deletethewords~extending ineach
direction'.
( Page66,clause34.4.3..line5 ) -Substitute'not'for'no'.
(Page78,..1nnexA )-Substitutethefollowingfor the existingentriesfor
153812:1981:
·/S1\/0. ,Title
IS 3812(Part1) :2003Specificationforpulverizedfuel ash :PartI For
usc aspozzolanaincement,cementmortarand
concrete(secondrevision)'
('Page79.AnnexA )._--Add thefollowing attheend:
41~')1No. Title
2116815/07-1
IS15388:2001 Specificationfor silica fume'
TO ~.
tW\U'"
IS456:2000PLAI.NANDREINFO~D CONCRETE-
CODEOF'PRACTICE
( FIJUrthRevision),
( Page13,clause5.2.1.1,line1 ) -Substitute'IS 3812 (Part1)'for
'Graderens3812'.
( Page13,clause5.2.1.2andcorrespondingNote) - Substitutethe
followingfortheexisting:
..Silicafumeconformingto IS15388maybeusedas partreplacementofcement
provideduniformblendingwiththecementisensured.
NOTE- Silica fume isusuallyusedin proportionof~to 10 percent of the cement
content of a mix.'
tPage
13.Noteunderclause5.2.1.3,line5 ) -Substitute'be'for'range
frombeing'!.
( Page25..clause10.3.3,line4 )- Deletethe word 'and'.
(Page65.clause34.2.4.2.line1 )-Substitute'on' for'or'.
[Page65.clause34.3.1(a)..line2I -Deletethewords~extending ineach
direction'.
( Page66,clause34.4.3..line5 ) -Substitute'not'for'no'.
(Page78,..1nnexA )-Substitutethefollowingfor the existingentriesfor
153812:1981:
·/S1\/0. ,Title
IS 3812(Part1) :2003Specificationforpulverizedfuel ash :PartI For
usc aspozzolanaincement,cementmortarand
concrete(secondrevision)'
('Page79.AnnexA )._--Add thefollowing attheend:
41~')1No. Title
2116815/07-1
IS15388:2001 Specificationfor silica fume'
(p.80,1-2.1.1,Ilf/oIfIMllabl,)-InlertthefoUowlftllnthetable:
•...
5.6
(Pag,81,TtJbl,21)-InsertthefollowiftlrowaftertheIMtrow:
'(1)
M'S
(2)
17.5
(3)
13,0
(4)
I."
(Pag,91,TtJbl,26,eMfNo.2,col2) -Subltitute'OMShortEd••
DilOOlltlnuou.'lor'OnIlhoitEd..Conti.....',
[PGI,96,G-1.l(c)./olWlIl/G]-Subltitute'MuJiII'/o,'My'um',
[Pagl96,G-l.1(d),,.,"'"]-Subltitute'31.1I/0''39.1I.
(CED2)
2
•...
5.6
(Pag,81,TtJbl,21)-InsertthefollowiftlrowaftertheIMtrow:
'(1)
M'S
(2)
17.5
(3)
13,0
(4)
I."
(Pag,91,TtJbl,26,eMfNo.2,col2) -Subltitute'OMShortEd••
DilOOlltlnuou.'lor'OnIlhoitEd..Conti.....',
[PGI,96,G-1.l(c)./olWlIl/G]-Subltitute'MuJiII'/o,'My'um',
[Pagl96,G-l.1(d),,.,"'"]-Subltitute'31.1I/0''39.1I.
(CED2)
2
18456:2000
IndianStandard
PLAINANDREINFORCEDCONCRETE
CODEOFPRACTICE
(FourthRevision)
FOREWORD
ThisIndianStandard(FourthRevision)was adoptedbytheBureauofIndianStandards,afterthedraftfinalized
. bytheCementandConcreteSectional CommitteehadbeenapprovedbytheCivilEngineeringDivisionCouncil.
Thisstandardwas firstpublishedin 1953underthetitle 'Codeofpracticeforplainandreinforcedconcretefor
general buildingconstruction'andsubsequentlyrevisedin1957.The code wasfurtherrevisedin 1964 and
publishedundermodifiedtitle 'Code ofpracticeforplainand
reinforcedconcrete',thusenlargingthe scopeof
useof thiscodetostructuresotherthan
generalbuildingconstructionalso. Thethird revisionwaspublishedin
1978,and it includedlimit stateapproachto design.This is thefourthrevisionof thestandard.Thisrevision
wastakenup witha viewto
keepingabreastwiththerapiddevelopmentin thefieldofconcretetechnologyand
to bringin furthermodifications/improvementsin
thelightofexperience gainedwhileusingtheearlierversion
of thestandard.
Thisrevisionincorporatesa
numberofimportantchanges.Themajorthrustin therevisionis on the following
lines:
a)Inrecent years.durabilityofconcretestructureshave becomethecause ofconcernto allconcrete
technologists.This has ledto the needto
codifythedurabilityrequirementsworld over.In thisrevision
of the
code.in ordertointroducein-builtprotectionfromfactorsaffectingastructure,earlierclauseon
durabilityhas beenelaboratedand adetailedclausecoveringdifferentaspectsof design ofdurable
structurehas beenincorporated.
b) Sampling andacceptancecriteriaforconcretehavebeen revised.Withthisrevisionacceptancecriteria
has beensimplifiedin line with theprovisionsgiven in BS 5328
(P8l14):1990 'Concrete: Part 4
Specificationfor theproceduresto
beusedinsampling,testingandassessingcomplianceof concrete'.
Someof thesignificant
changesincorporatedin Section2 are asfollows:
a) All the threegradesofordinary Portland
cement,namely33grade,43 gradeand53 gradeandsulphate
resisting
Portlandcement have been includedin the list of
typesofcementused(inadditionto other
typesof cement).
b) Thepermissiblelimitsforsolidsinwaterhavebeenmodifiedkeepinginviewthedurabilityrequirements.
c) Theclauseonadmixtureshas beenmodifiedinviewoftheavailabilityof new types of admixtures
includingsuperplasticizers.
d) In Table2 'Grades of Concrete',
gradeshigherthanM 40 havebeenincluded.
e) It has been
recommendedthatminimumgradeofconcreteshallbenot less than M 20inreinforced
concretework(seealso6.1.3).
f)Theformulaforestimationof modulusofelasticityofconcretehas been revised.
g) In the absenceof propercorrelation betweencompactingfactor,vee-beetime and slump,workability
has now beenspecifiedonly in termsof
slumpin linewiththeprovisionsin BS 5328
(Parts1 to4).
h)Durabilityclausehasbeenenlargedtoincludedetailedguidanceconcerningthefactorsaffectingdurability.
The table on'EnvironmentalExposureConditions'has beenmodifiedto include 'very severe' and
'extreme'exposure conditions. This clause also covers requirements for shape and size of member,
depthofconcretecover,concretequality,requirementagainstexposuretoaggressivechemicalandsulphate
attack,minimumcementrequirementand maximumwatercementratio,limitsofchloridecontent.alkali
silicareaction,andimportanceofcompaction,finishingand
curing.
j)Aclauseon-'QualityAssuranceMeasures'has beenincorporatedto givedueemphasisto goodpractices
ofconcreting.
k) Properlimitshavebeenintroducedonthe
accuracyofmeasuringequipmentstoensureaccurate batching
ofconcrete.
2116
BIS/07-:.!.
IndianStandard
PLAINANDREINFORCEDCONCRETE
CODEOFPRACTICE
(FourthRevision)
FOREWORD
ThisIndianStandard(FourthRevision)was adoptedbytheBureauofIndianStandards,afterthedraftfinalized
. bytheCementandConcreteSectional CommitteehadbeenapprovedbytheCivilEngineeringDivisionCouncil.
Thisstandardwas firstpublishedin 1953underthetitle 'Codeofpracticeforplainandreinforcedconcretefor
general buildingconstruction'andsubsequentlyrevisedin1957.The code wasfurtherrevisedin 1964 and
publishedundermodifiedtitle 'Code ofpracticeforplainand
reinforcedconcrete',thusenlargingthe scopeof
useof thiscodetostructuresotherthan
generalbuildingconstructionalso. Thethird revisionwaspublishedin
1978,and it includedlimit stateapproachto design.This is thefourthrevisionof thestandard.Thisrevision
wastakenup witha viewto
keepingabreastwiththerapiddevelopmentin thefieldofconcretetechnologyand
to bringin furthermodifications/improvementsin
thelightofexperience gainedwhileusingtheearlierversion
of thestandard.
Thisrevisionincorporatesa
numberofimportantchanges.Themajorthrustin therevisionis on the following
lines:
a)Inrecent years.durabilityofconcretestructureshave becomethecause ofconcernto allconcrete
technologists.This has ledto the needto
codifythedurabilityrequirementsworld over.In thisrevision
of the
code.in ordertointroducein-builtprotectionfromfactorsaffectingastructure,earlierclauseon
durabilityhas beenelaboratedand adetailedclausecoveringdifferentaspectsof design ofdurable
structurehas beenincorporated.
b) Sampling andacceptancecriteriaforconcretehavebeen revised.Withthisrevisionacceptancecriteria
has beensimplifiedin line with theprovisionsgiven in BS 5328
(P8l14):1990 'Concrete: Part 4
Specificationfor theproceduresto
beusedinsampling,testingandassessingcomplianceof concrete'.
Someof thesignificant
changesincorporatedin Section2 are asfollows:
a) All the threegradesofordinary Portland
cement,namely33grade,43 gradeand53 gradeandsulphate
resisting
Portlandcement have been includedin the list of
typesofcementused(inadditionto other
typesof cement).
b) Thepermissiblelimitsforsolidsinwaterhavebeenmodifiedkeepinginviewthedurabilityrequirements.
c) Theclauseonadmixtureshas beenmodifiedinviewoftheavailabilityof new types of admixtures
includingsuperplasticizers.
d) In Table2 'Grades of Concrete',
gradeshigherthanM 40 havebeenincluded.
e) It has been
recommendedthatminimumgradeofconcreteshallbenot less than M 20inreinforced
concretework(seealso6.1.3).
f)Theformulaforestimationof modulusofelasticityofconcretehas been revised.
g) In the absenceof propercorrelation betweencompactingfactor,vee-beetime and slump,workability
has now beenspecifiedonly in termsof
slumpin linewiththeprovisionsin BS 5328
(Parts1 to4).
h)Durabilityclausehasbeenenlargedtoincludedetailedguidanceconcerningthefactorsaffectingdurability.
The table on'EnvironmentalExposureConditions'has beenmodifiedto include 'very severe' and
'extreme'exposure conditions. This clause also covers requirements for shape and size of member,
depthofconcretecover,concretequality,requirementagainstexposuretoaggressivechemicalandsulphate
attack,minimumcementrequirementand maximumwatercementratio,limitsofchloridecontent.alkali
silicareaction,andimportanceofcompaction,finishingand
curing.
j)Aclauseon-'QualityAssuranceMeasures'has beenincorporatedto givedueemphasisto goodpractices
ofconcreting.
k) Properlimitshavebeenintroducedonthe
accuracyofmeasuringequipmentstoensureaccurate batching
ofconcrete.
2116
BIS/07-:.!.
IS456:2000
m) The clause on 'ConstructionJoints' hasbeenmodified.
n) Theclauseon'Inspection'hasbeenmodifiedto give more emphasison quality assurance.
The significantchanges incorporatedin Section 3 are asfollows:
a)Requirementsfor 'Fire Resistance' have been furtherdetailed.
h) 'The figure for estimation ofmodificationfactor for tensionreinforcementused in calculation of basic
valuesofspanto effectivedepth to control the deflection offlexuralmemberhas been modified.
c)Recommendationsregardingeffectivelength of cantileverhave been added.
d)Recommendationsregardingdeflectiondue to lateral loads have been added.
e)Recommendationsfor adjustmentsof support momentsin restrainedslabs have been included.
f)Int.hedeteminationof
effectivelength ofcompressionmembers.stabilityindex has been introducedto
determine sway or noswayconditions.
g)Recommendationshavebeenmade for lap lengthof hooksfor barsin direct tensionand flexuraltension.
h)Recommendationsregardingstrength of welds have beenmodified.
j)Recommendationsregarding cover toreinforcementhave beenmodified.Cover has been specified
based on durabilityrequirementsfor differentexposureconditions. The term 'nominal covert has been
introduced. The cover has now been specified based on durability requirement as well as for fire
requirements.
The significantchangeincorporatedin Section4 is themodificationof theclauseon
Walls.The modifiedclause
includesdesign of walls against horizontal
shear.
In Section 5 on limit state method a new clause has been added forcalculationof enhanced shear strength of
sectionsclose tosupports.Some modificationshave also been made in the clause onTorsion. Formulafor
calculationof crack widthhasbeen added (separatelygiven in AnnexF).
\Vnrkingstress methodhas now been given in Annex B so as to give greateremphasis to limit state design. In
thisAnnex, modificanonsregardingtorsionand enhancedshear strengthon the same lines as in Section 5 have
beenmade,
Whilstthecommonmethods of design and construction have been covered in this code, special systems of
designandconstructionof any plain or reinforcedconcretestructurenotcovered by thiscode may be permitted
on production ofsatisfactoryevidence regarding their adequacy and safetybyanalysis or test or both
(see19).
In thiscodeithas beenassumed that the design of plain and reinforcedcement concrete work is entrusted to a
qualifiedengineerandthat theexecutionof cementconcreteworkiscarriedout underthedirectionof a qualified
and experiencedsupervisor.
In theformulationof this standard, assistance
hasbeen derived from thefollowingpublications:
BS
5328: Part1 :1991Concrete:Part 1Guide to specifyingconcrete, British Standards Institution
BS5328: Part2 :1991Concrete : Part 2 Methodsforspecifying concrete mixes, British Standards
Institution
BS 5328 : Part 3:1990Concrete: Part 3 Specificationfor tbeproceduresto be used in producing and
transporting
concrete.British Standards Institution
BS
532R:Part4 :1990Concrete; Part 4Specificationfor the proced.urestobeused in sampling, testing
andassessingcomplianceof concrete, British StandardsInstitution
BS 8110 : Part 1 :
1985Structural use of concrete: ParttCode of practice for design and construction,
British StandardsInstitution
BS
RItO:Part 2 : 1985 Structural use ofconcrete:Part 2 Code of practice for special circumstances,
British StandardsInstitution
ACT319
~1989Buildingcoderequirementsfor reinforcedconcrete, AmericanConcrete Institute
AS 3600 : 1988Concrete structures.StandardsAssociationof Australia
2
m) The clause on 'ConstructionJoints' hasbeenmodified.
n) Theclauseon'Inspection'hasbeenmodifiedto give more emphasison quality assurance.
The significantchanges incorporatedin Section 3 are asfollows:
a)Requirementsfor 'Fire Resistance' have been furtherdetailed.
h) 'The figure for estimation ofmodificationfactor for tensionreinforcementused in calculation of basic
valuesofspanto effectivedepth to control the deflection offlexuralmemberhas been modified.
c)Recommendationsregardingeffectivelength of cantileverhave been added.
d)Recommendationsregardingdeflectiondue to lateral loads have been added.
e)Recommendationsfor adjustmentsof support momentsin restrainedslabs have been included.
f)Int.hedeteminationof
effectivelength ofcompressionmembers.stabilityindex has been introducedto
determine sway or noswayconditions.
g)Recommendationshavebeenmade for lap lengthof hooksfor barsin direct tensionand flexuraltension.
h)Recommendationsregardingstrength of welds have beenmodified.
j)Recommendationsregarding cover toreinforcementhave beenmodified.Cover has been specified
based on durabilityrequirementsfor differentexposureconditions. The term 'nominal covert has been
introduced. The cover has now been specified based on durability requirement as well as for fire
requirements.
The significantchangeincorporatedin Section4 is themodificationof theclauseon
Walls.The modifiedclause
includesdesign of walls against horizontal
shear.
In Section 5 on limit state method a new clause has been added forcalculationof enhanced shear strength of
sectionsclose tosupports.Some modificationshave also been made in the clause onTorsion. Formulafor
calculationof crack widthhasbeen added (separatelygiven in AnnexF).
\Vnrkingstress methodhas now been given in Annex B so as to give greateremphasis to limit state design. In
thisAnnex, modificanonsregardingtorsionand enhancedshear strengthon the same lines as in Section 5 have
beenmade,
Whilstthecommonmethods of design and construction have been covered in this code, special systems of
designandconstructionof any plain or reinforcedconcretestructurenotcovered by thiscode may be permitted
on production ofsatisfactoryevidence regarding their adequacy and safetybyanalysis or test or both
(see19).
In thiscodeithas beenassumed that the design of plain and reinforcedcement concrete work is entrusted to a
qualifiedengineerandthat theexecutionof cementconcreteworkiscarriedout underthedirectionof a qualified
and experiencedsupervisor.
In theformulationof this standard, assistance
hasbeen derived from thefollowingpublications:
BS
5328: Part1 :1991Concrete:Part 1Guide to specifyingconcrete, British Standards Institution
BS5328: Part2 :1991Concrete : Part 2 Methodsforspecifying concrete mixes, British Standards
Institution
BS 5328 : Part 3:1990Concrete: Part 3 Specificationfor tbeproceduresto be used in producing and
transporting
concrete.British Standards Institution
BS
532R:Part4 :1990Concrete; Part 4Specificationfor the proced.urestobeused in sampling, testing
andassessingcomplianceof concrete, British StandardsInstitution
BS 8110 : Part 1 :
1985Structural use of concrete: ParttCode of practice for design and construction,
British StandardsInstitution
BS
RItO:Part 2 : 1985 Structural use ofconcrete:Part 2 Code of practice for special circumstances,
British StandardsInstitution
ACT319
~1989Buildingcoderequirementsfor reinforcedconcrete, AmericanConcrete Institute
AS 3600 : 1988Concrete structures.StandardsAssociationof Australia
2
-....
IS456:2000
DIN 1045July 1988Structuraluseof concrete,designandconstruction. Deutschcs lnsritutfurNormungE.V.
CEB..FIP Model code 1990, Comite Euro..International Du Bclon
The composition of the technical committee
responsiblefor the formulationofthis
standardisgivenIn
AnnexH.
For the purpose ofdecidingwhether a particular requirement of thisstandardis complied with,thefinal value,
observedor calculated, expressingtheresult of a test or analysis shallherounded off inaccordancewith
IS
2:1960 'Rules
forrounding off numerical values(revised)'.The numberofsignificantplaces retained in the
roundedoff valueshouldbethe sameasthatof thespecifiedvalueillthis standard.
3
IS456:2000
DIN 1045July 1988Structuraluseof concrete,designandconstruction. Deutschcs lnsritutfurNormungE.V.
CEB..FIP Model code 1990, Comite Euro..International Du Bclon
The composition of the technical committee
responsiblefor the formulationofthis
standardisgivenIn
AnnexH.
For the purpose ofdecidingwhether a particular requirement of thisstandardis complied with,thefinal value,
observedor calculated, expressingtheresult of a test or analysis shallherounded off inaccordancewith
IS
2:1960 'Rules
forrounding off numerical values(revised)'.The numberofsignificantplaces retained in the
roundedoff valueshouldbethe sameasthatof thespecifiedvalueillthis standard.
3
SECTION 1 GENERAL
IS456:2000
1 SCOPE
1.1 This standarddeals with the generalstructuraluse
ofplain andreinforced concrete.
1.1.1 For the purpose of this standard, plain concrete
structures are those where reinforcement,if provided
is ignoredfordeterminationof strengthof thestructure.
1.2Special requirementsof structures,such as shells,
foldedplates,arches.bridges,chimneys,blastresistant
structures, hydraulicstructures,liquidretaining
structuresand earthquakeresistantstructures,covered
in respective standards have not been covered in this
standard; these standards shall
beusedin.conjunction
with
thisstandard.
2REFERENCES
TheIndianStandardslisted in Annex A contain
provisionswhich throughreferencein this text,
constitute provisions ofthilstandard. At the time of
publication,
theedition.indicatedwere valid. All
standardsaresubjecttorevisionandparties to
agreements
based
onthis standard are encouragedto
investigatethepossibilityofapplying themostrecent
editions of the standards indicated in AnnexA. .
3TERMINOLOGY
For thepurposeofthisstandard,thedefinitionsBiven
inIS 4845and IS 6461 (Parts 1 to 12) shall generally
apply.
4 SYMBOLS
For thepurpose ofthisstandard,the followingletter
symbolsshallhavethe
mcaninaindicatedagainsteach;
whereother symbolsare used.theyareexplainedat
the appropriate place:
A- Area
b- Breadthofbeam,orshorterdimension
of arectangulercolumn
bet"-Effective width of slab
b, Effectivewidthofflanac
b.,-Breadthofweb or rib
D -Overalldepth of beam or slab or
diameter of column; dimension of a
rectangularcolumn inthedirection
under consideration
Dr -Thicknessof flange
DL- Dead load
d- Effective depth of beam or slab
d'- Depth of compression reinforcement
from the highly compressedface
E
c
-.Modulus ofelasticityof concrete
EL-Earthquakeload
E.-Modulusofelasticityof
steel
e-Eccentricity
let.-Characteristiccubecompressive
stren.thofconcrete
t;-Modulusofruptureofconcrete
(flexuraltensileaU-oath)
ft1-Splittin,tensilelU'eftltbofconcrete
t,-DesipItren,th
I,-CharacteriaticItrenJthofsteel
H.-Unsupportedhei,htof wall
H -Effectivehei,htof wall
we
Ie(-Effective moment of inertia
1-Momentof inertiaof the gross section
'f
excludingreinforcement
I,-Momentofintertiaofcracked section
K-Stiffnessof member
k-Constant or coefficientorfactor
L
d-Developmentlength
U-Live load or imposed load
L
w-Horizontaldistancebetweencentresof
lateralrestraint
-Length of a column orbeambetween
adequatelateralrestraintsor the
unsupportedlength of a column
ler-Effective spanof
beamor slab or
effective length of column
lea-Effectivelength aboutx-xaxis
I-Effectiveleng~abouty-yaxis
ey
I.-Clear span, face-to-face of supports
I'-I:for shorterofthetwo spans at right
n
&lgles
I"-Lengthofshorterlide of slab
ly-Lin.thofloftieraide of slab
1
0-Distancebetweenpoints ofzerolnomen..in abeam
I.-Spanin thedirectioninwhich
momentsare determined, centre to
centreofsupports
1
2-Spantransv~se toI"centreto centre
of supports
I'-
1
2
for the shorter ofthe;continuous
2
spans
M-Bendin.moment
m-Modularratio
n-Number of samples
p-Axialloadon acompressionmember
q"
Calculatedmaximumbearingpressure
11
IS456:2000
1 SCOPE
1.1 This standarddeals with the generalstructuraluse
ofplain andreinforced concrete.
1.1.1 For the purpose of this standard, plain concrete
structures are those where reinforcement,if provided
is ignoredfordeterminationof strengthof thestructure.
1.2Special requirementsof structures,such as shells,
foldedplates,arches.bridges,chimneys,blastresistant
structures, hydraulicstructures,liquidretaining
structuresand earthquakeresistantstructures,covered
in respective standards have not been covered in this
standard; these standards shall
beusedin.conjunction
with
thisstandard.
2REFERENCES
TheIndianStandardslisted in Annex A contain
provisionswhich throughreferencein this text,
constitute provisions ofthilstandard. At the time of
publication,
theedition.indicatedwere valid. All
standardsaresubjecttorevisionandparties to
agreements
based
onthis standard are encouragedto
investigatethepossibilityofapplying themostrecent
editions of the standards indicated in AnnexA. .
3TERMINOLOGY
For thepurposeofthisstandard,thedefinitionsBiven
inIS 4845and IS 6461 (Parts 1 to 12) shall generally
apply.
4 SYMBOLS
For thepurpose ofthisstandard,the followingletter
symbolsshallhavethe
mcaninaindicatedagainsteach;
whereother symbolsare used.theyareexplainedat
the appropriate place:
A- Area
b- Breadthofbeam,orshorterdimension
of arectangulercolumn
bet"-Effective width of slab
b, Effectivewidthofflanac
b.,-Breadthofweb or rib
D -Overalldepth of beam or slab or
diameter of column; dimension of a
rectangularcolumn inthedirection
under consideration
Dr -Thicknessof flange
DL- Dead load
d- Effective depth of beam or slab
d'- Depth of compression reinforcement
from the highly compressedface
E
c
-.Modulus ofelasticityof concrete
EL-Earthquakeload
E.-Modulusofelasticityof
steel
e-Eccentricity
let.-Characteristiccubecompressive
stren.thofconcrete
t;-Modulusofruptureofconcrete
(flexuraltensileaU-oath)
ft1-Splittin,tensilelU'eftltbofconcrete
t,-DesipItren,th
I,-CharacteriaticItrenJthofsteel
H.-Unsupportedhei,htof wall
H -Effectivehei,htof wall
we
Ie(-Effective moment of inertia
1-Momentof inertiaof the gross section
'f
excludingreinforcement
I,-Momentofintertiaofcracked section
K-Stiffnessof member
k-Constant or coefficientorfactor
L
d-Developmentlength
U-Live load or imposed load
L
w-Horizontaldistancebetweencentresof
lateralrestraint
-Length of a column orbeambetween
adequatelateralrestraintsor the
unsupportedlength of a column
ler-Effective spanof
beamor slab or
effective length of column
lea-Effectivelength aboutx-xaxis
I-Effectiveleng~abouty-yaxis
ey
I.-Clear span, face-to-face of supports
I'-I:for shorterofthetwo spans at right
n
&lgles
I"-Lengthofshorterlide of slab
ly-Lin.thofloftieraide of slab
1
0-Distancebetweenpoints ofzerolnomen..in abeam
I.-Spanin thedirectioninwhich
momentsare determined, centre to
centreofsupports
1
2-Spantransv~se toI"centreto centre
of supports
I'-
1
2
for the shorter ofthe;continuous
2
spans
M-Bendin.moment
m-Modularratio
n-Number of samples
p-Axialloadon acompressionmember
q"
Calculatedmaximumbearingpressure
11
IS456:2000
qn-Calculatedmaximumbearingpressure
of soil
r- Radius
s- Spacingofstirrupsorstandard
deviation
T -Torsionalmoment
-Wallthickness
V- Shearforce
W- Totalload
WL Windload
w- Distributedloadper unitarea
W
d -Distributeddeadload per unitarea
WI -Distributedimposedloadperunitarea
x- Depthofneutralaxis
Z Modulusofsection
l -Leverarm
a.8-Anile orratio
Y
r
-
Partialsafetyfactorfor load
..
J:!
Y
m
-Partialsafetyfactorformaterial
8
m
Percentagereductionin moment
e
ec -Creepstrainof concreteG&:hI;-Permissiblestressin concrete in
bendingcompression
a&;e-Permissible.stressin concreteindirect
compression
oftK:-Permissiblestressin metalin·direct
compression
GM:-Permissible stressinsteelin
compression
(J",-Permissiblestress in steel intension
a"v-Permissibletensile stress in shear
reinforcement
t
hd
-Designbondstress
t&; Shearstress inconcrete
t
e
•
mI&X
-Maximum shear stress in concrete
withshear
reinforcement
'tv-Nominalshearstress
,-Diameterof bar
qn-Calculatedmaximumbearingpressure
of soil
r- Radius
s- Spacingofstirrupsorstandard
deviation
T -Torsionalmoment
-Wallthickness
V- Shearforce
W- Totalload
WL Windload
w- Distributedloadper unitarea
W
d -Distributeddeadload per unitarea
WI -Distributedimposedloadperunitarea
x- Depthofneutralaxis
Z Modulusofsection
l -Leverarm
a.8-Anile orratio
Y
r
-
Partialsafetyfactorfor load
..
J:!
Y
m
-Partialsafetyfactorformaterial
8
m
Percentagereductionin moment
e
ec -Creepstrainof concreteG&:hI;-Permissiblestressin concrete in
bendingcompression
a&;e-Permissible.stressin concreteindirect
compression
oftK:-Permissiblestressin metalin·direct
compression
GM:-Permissible stressinsteelin
compression
(J",-Permissiblestress in steel intension
a"v-Permissibletensile stress in shear
reinforcement
t
hd
-Designbondstress
t&; Shearstress inconcrete
t
e
•
mI&X
-Maximum shear stress in concrete
withshear
reinforcement
'tv-Nominalshearstress
,-Diameterof bar
IS456:2000
SECTION 2MATERIALS,WORKMANSHIP,
INSPECTIONANDTESTING
5MATERIALS
s.tCement
The cement used shall he any of the following and the
typeselected shouldbeappropriate for the intended
use:
a)33GradeordinaryPortlandcement
conforming to IS 269
b) 43
GradeordinaryPortlandcement
conforming to IS 8112
c)S3GradeordinaryPortlandcement
conforming to IS 12269
d) Rapid hardening Portlandcement conforming
to IS 8041
e)Portlandslag cementconformingto IS
4;5
f)Portland pozzolana cement (flyashbased)
conforming to IS 1489 (Part 1)
g)Portlandpozzolanacement (calcined clay
based) conforming
to IS 1489(Part 2)
h)
Hydrophobiccement conforming to IS 8043
j)Low heatPortlandcementconformingto
IS 12600
k)
SulphateresistingPortlandcement
conformingtoIS 12330
OthercombinationsofPortlandcement with mineral
admixtures
(see$.2) ofqualityconformingwith
relevant
IndianStandards laid down may also be used
in the
manufactureof concrete provided that there are
satisfactorydationtheirsuitability,suchas
performance test
~concrete containing them.
5.1.1 Low heatPortlandcementconformingto
IS 12600 shall beusedwith adequateprecautionswith
regard to removal
offormwork, etc.
5.1.ZHiahalumina cement conformingtoIS 6452 or
supersulphatedcementconforming to IS 6909maybe
used
onlyunder special circumstances with the prior
approvalof theengineer-in-charge.Specialistliterature
Inay
beconsuItedforguidanceregardingthe use of
these types of cements.
5.1.3The attention of the engineers-in-charge and
usersofcementis drawn to the fact that quality of
various
cementsmentioned in5.1is tobedetermined
on the basis of its conformity to the performance
characteristicsgiven in the respective Indian Standard
Specificationforthatcement. Any trade-mark orany
tradenameindicatingany special features notcovered
in.the standardoranyqualification or otherspecial
performancecharacteristicssometimesclaimedl
indicatedon the bass or containersor inadvertisements
alongsidethe'Statutory QualityMarking' or otherwise
13
have no relation whatsoever withthecharacteristics
guaranteed by the Quality Marking as relevant to that
cement. Consumers are, therefore, advised to
goby
thecharacteristics
asgiven inthecorresponding
IndianStandardSpecificationor seekspecialist
advise to avoid any problem in concrete making and
construction.
5.2MineralAdmixtures
5.1.1Pozzolanas
Pozzolanic materials conforming to relevant Indian
Standardsmaybeusedwiththe permissionofthe
engineer-in-charge,provided uniform blending with
cement is ensured.
5.2.1.1Fly ash(pulverizedfuelash)
FlyashconformingtoGrade1 of IS 3812maybe
usedaspart replacementofordinary Portland cement
provided uniform blending with cement is ensured.
5.2.1.2 Silicafume
Silica fume conforming to a standard approved by the
deciding authority
maybeusedas part replacement of
cement provided uniform blending with the cement is
ensured.
NOTE-The
silicafume (very fine non-crystalline silicon
dioxide)isaby-productofthel1UU1ufactureofsilicon,ferrosilicon
or the like. fromquartzandcarbonin electric arcfurnace.It is
usuallyusedinproportionofSto 10percentofthecementcontent
ofamix,
5.1.1.3Rice husk ash
Rice husk ashgivingrequiredperformanceand
uniformitycharacteristics
maybe used with the
approval
ofthe deciding authority.
NOTE-Ricehusk esh isproducedby burning rice husk
and
containlargeproportionof silica. Toachieveamorphousstate,
ricehuskahaybeburntat controlledtemperature,Itisnecessary
toevoluat8theproductfromaparticularsourceforperformance
andunirofmitysince itconran,efrom beinlasdeleteriousas
silt when.~ncorporated inconcrete.Waterdemandanddryinl
shrinkage',shouldbe studiedbeforeusingricehusk.
5.2.1.4M'takaoline
Metakaollnehavingfinenessbetween700to
900m
2
/kg'maybe used as pozzolanic material in
concrete.
NOTE-MetokQolineis
obtainedbycalcination ofpureor
refinedkoollnticclayorDtemperaturebetween6500Cand8~O°C,
followedby.rindin.toachieveafinenessof 700 to 900m:llka.
TheresultiDImaterialhOIhilh.'pozzoianicity.
S.2.2GroundGranulatedBlastFurnaceSlag
Ground granulated blast furnace slag obtainedby
grinding granulated blast furnace slag conforming to
IS 12089
maybe used as part replacement of ordinary
SECTION 2MATERIALS,WORKMANSHIP,
INSPECTIONANDTESTING
5MATERIALS
s.tCement
The cement used shall he any of the following and the
typeselected shouldbeappropriate for the intended
use:
a)33GradeordinaryPortlandcement
conforming to IS 269
b) 43
GradeordinaryPortlandcement
conforming to IS 8112
c)S3GradeordinaryPortlandcement
conforming to IS 12269
d) Rapid hardening Portlandcement conforming
to IS 8041
e)Portlandslag cementconformingto IS
4;5
f)Portland pozzolana cement (flyashbased)
conforming to IS 1489 (Part 1)
g)Portlandpozzolanacement (calcined clay
based) conforming
to IS 1489(Part 2)
h)
Hydrophobiccement conforming to IS 8043
j)Low heatPortlandcementconformingto
IS 12600
k)
SulphateresistingPortlandcement
conformingtoIS 12330
OthercombinationsofPortlandcement with mineral
admixtures
(see$.2) ofqualityconformingwith
relevant
IndianStandards laid down may also be used
in the
manufactureof concrete provided that there are
satisfactorydationtheirsuitability,suchas
performance test
~concrete containing them.
5.1.1 Low heatPortlandcementconformingto
IS 12600 shall beusedwith adequateprecautionswith
regard to removal
offormwork, etc.
5.1.ZHiahalumina cement conformingtoIS 6452 or
supersulphatedcementconforming to IS 6909maybe
used
onlyunder special circumstances with the prior
approvalof theengineer-in-charge.Specialistliterature
Inay
beconsuItedforguidanceregardingthe use of
these types of cements.
5.1.3The attention of the engineers-in-charge and
usersofcementis drawn to the fact that quality of
various
cementsmentioned in5.1is tobedetermined
on the basis of its conformity to the performance
characteristicsgiven in the respective Indian Standard
Specificationforthatcement. Any trade-mark orany
tradenameindicatingany special features notcovered
in.the standardoranyqualification or otherspecial
performancecharacteristicssometimesclaimedl
indicatedon the bass or containersor inadvertisements
alongsidethe'Statutory QualityMarking' or otherwise
13
have no relation whatsoever withthecharacteristics
guaranteed by the Quality Marking as relevant to that
cement. Consumers are, therefore, advised to
goby
thecharacteristics
asgiven inthecorresponding
IndianStandardSpecificationor seekspecialist
advise to avoid any problem in concrete making and
construction.
5.2MineralAdmixtures
5.1.1Pozzolanas
Pozzolanic materials conforming to relevant Indian
Standardsmaybeusedwiththe permissionofthe
engineer-in-charge,provided uniform blending with
cement is ensured.
5.2.1.1Fly ash(pulverizedfuelash)
FlyashconformingtoGrade1 of IS 3812maybe
usedaspart replacementofordinary Portland cement
provided uniform blending with cement is ensured.
5.2.1.2 Silicafume
Silica fume conforming to a standard approved by the
deciding authority
maybeusedas part replacement of
cement provided uniform blending with the cement is
ensured.
NOTE-The
silicafume (very fine non-crystalline silicon
dioxide)isaby-productofthel1UU1ufactureofsilicon,ferrosilicon
or the like. fromquartzandcarbonin electric arcfurnace.It is
usuallyusedinproportionofSto 10percentofthecementcontent
ofamix,
5.1.1.3Rice husk ash
Rice husk ashgivingrequiredperformanceand
uniformitycharacteristics
maybe used with the
approval
ofthe deciding authority.
NOTE-Ricehusk esh isproducedby burning rice husk
and
containlargeproportionof silica. Toachieveamorphousstate,
ricehuskahaybeburntat controlledtemperature,Itisnecessary
toevoluat8theproductfromaparticularsourceforperformance
andunirofmitysince itconran,efrom beinlasdeleteriousas
silt when.~ncorporated inconcrete.Waterdemandanddryinl
shrinkage',shouldbe studiedbeforeusingricehusk.
5.2.1.4M'takaoline
Metakaollnehavingfinenessbetween700to
900m
2
/kg'maybe used as pozzolanic material in
concrete.
NOTE-MetokQolineis
obtainedbycalcination ofpureor
refinedkoollnticclayorDtemperaturebetween6500Cand8~O°C,
followedby.rindin.toachieveafinenessof 700 to 900m:llka.
TheresultiDImaterialhOIhilh.'pozzoianicity.
S.2.2GroundGranulatedBlastFurnaceSlag
Ground granulated blast furnace slag obtainedby
grinding granulated blast furnace slag conforming to
IS 12089
maybe used as part replacement of ordinary
IS456:2000
Portland cements provided uniform blending with
cement is ensured.
5.3Allre.ates
Aggregates shallcomplywiththerequirementsof
IS 383. As far as possiblepreferenceshallbegivento
naturalaggregates...
5.3.1Othertypes ofaggregatessuch as sialand
crushedoverbumt brick or tile, whichmay befound
suitable with regard to strength.durabilityofconcrete
and
freedomfromharmfuleffectsmaybeusedforplain
concrete members. but such
aggregatesshould not
contain
morethan
0.5percentofsulphatesas SO]and
should not absorb more than 10percentof theirown
massofwater,
5.3.2HeavyweightaggreiatesOflight weight
aggregatessuchas bloatedclayaggregatesandsintered
flyash aggregatesmayalsobeused provided the
engineer-in-chargeis satisfiedwiththe data on the
propertiesof concretemade
withthem.NOTE-Someof theprovisioDIofthecode would require
modIficationwhenthesealPlatesareused:speclaliltliteratuJe
maybeconsultedforauidance.
5.3.3Sizt~fAggregate
Thenominalmaximumsizeofcoarseaggregateshould
beaslargeas possiblewithinthe limitsspecifiedbut
in no casegreaterthanone-fourthof the minimum
thicknessof the member,providedthat the concrete
canbeplacedwithoutdifficultyso as tosurroundall
reinforcementthoroughlyand fill the comers of the
form,For mostwork,20 nun
alareaateissuitable.
Wherethere is norestrictionto theflow ofconcrete
intosections,40 nun orlaraorsizemaybepermitted.
Inconcreteelementswiththinsections,closelyspaced
reinforcementor small
cover,considerationshouldbe
liven to the
useof 10mmnominalmaximumlize.
Plumsabove 160 nun anduptoanyreuonableaize
maybeusedinplainconcreteworkup to amaximum
limit of 20 percentbyvolumeofconcrete when
specificallypermittedbytheenaineer-in-charao.The
plumsshallbedistributedevenlyandIhallbenotcloser
than 1'0mm fromthe lurface.
5.3.3.1Forheav.iJyreinforcedconcretemembenu
in theelseof ribsof main beams,the nominal
maximum
aizeof the
a'lf'lateIhould usuallybe
re.trietedto~mmlei.thantheminimumcleareli.tanee
betweenthemainbarsorSmmlellthantheminimum
cover to thereinforcementwhicheveri.Imaller.
5.3.4 Coarse and finealsrelateIhallbe batched
separately.All.in-alar.,ltemaybeusedonlywhere
lpecificallypermittedbythoenlineer-in-char,e.
1.4Water
.Waterused formixin,and cunn'lhallbeclean and
14
freefrominjuriousamountsofoils.acids,alkalis,salta,
sugar,organicmaterialsor othersubstancesthat may
bedeleterioustoconcreteor steel.
Potablewater isgenerallyconsidered satisfactory
formixinaconcrete.As a guide thefollowing
concentrationsrepresent themaximumpennissible
values:
a) Toneutralize100 ml sample of water,usir.1
phenolphthaleinas anindicator,it should not
require morethan'mlof0.02nonnal NaOH.
The details oftestareaiven in 8.1ofIS
3025(Part 22).
b) Toneutralize100 ml sample of water,uains
mixedindicator, itshouldnotrequiremore
than2'ml of 0.02nonnalH
2SO
•.The details
oftestshall beasgivenin 8ofIS3025
(Part 23).
c)Permissiblelimits forsolids shallbeasliven
inTable1.
5.4.1 Incaseofdoubtregardinl development of
strength.the suitabilityof waterformakingconcrete
shallbeascertainedbythecompressivestreolthand
initialsettingtimetestsspecifiedin5.4.1.1and5.4.1.3.
5.4.1.1Thesample of watertakenforteslin,Ihall
representthewater proposedtobeusedforconcreting,
dueaccountbeingpaidtoseasonalvariation.The
sampleshall notreceive anytreatmentbefore te_un,
otherthanthatenvisagedintheregularsupplyofwater
proposedforuseinconcrete.Thesampleshallbeltored
in acleancontainerprevio~lly rinsedoutwithlimilar
water.
5.4.1.2Averalo 28 dayscompressiveItten.thof at
least
three
l~Onunconcretecubespreparedwithwater
proposedto beusedshall notbelellthan90percent
of the
averageof
strenlthofthreesimilar concrete
cubes
preparedwithdiltilledwater,Th.
cube••hall
beprepared.curedand testedinaccordancewiththe
requirementsof IS516.
5.4.1.3 Theinitial••ttinltimeofte.tblockmadewith
theappropriatecementandthewaterpropolldtobe
used.hallnotbele••than30 min and.hallnotdlff.
by±30min fromthe initial.etlinatime of control
teltblockpreparedwiththelamecement,anddiltiJled
water.Theteltblock.,hanbepreparedandtiltedIn
accordancewiththerequirementaof IS4031(P.n5).
5.4.1ThepH valueof water,hallbenotlellthan 6.
5.4.3Sea Water
Mixinl or curin, ofconcretewith.eawalerilnot
recommendedbecause'ofPf"Onceofharmful.lltlin
...water.UnderunavoidableCircumltaneel1Mwater
maybeusedformixin.orcuriolinplainconcretewith
noembeddedsteelafterhayiJlllivendueconllderation
toposlible.disadvantapaandprecaution.includin,UII
ofappropriatecementsystem.
Portland cements provided uniform blending with
cement is ensured.
5.3Allre.ates
Aggregates shallcomplywiththerequirementsof
IS 383. As far as possiblepreferenceshallbegivento
naturalaggregates...
5.3.1Othertypes ofaggregatessuch as sialand
crushedoverbumt brick or tile, whichmay befound
suitable with regard to strength.durabilityofconcrete
and
freedomfromharmfuleffectsmaybeusedforplain
concrete members. but such
aggregatesshould not
contain
morethan
0.5percentofsulphatesas SO]and
should not absorb more than 10percentof theirown
massofwater,
5.3.2HeavyweightaggreiatesOflight weight
aggregatessuchas bloatedclayaggregatesandsintered
flyash aggregatesmayalsobeused provided the
engineer-in-chargeis satisfiedwiththe data on the
propertiesof concretemade
withthem.NOTE-Someof theprovisioDIofthecode would require
modIficationwhenthesealPlatesareused:speclaliltliteratuJe
maybeconsultedforauidance.
5.3.3Sizt~fAggregate
Thenominalmaximumsizeofcoarseaggregateshould
beaslargeas possiblewithinthe limitsspecifiedbut
in no casegreaterthanone-fourthof the minimum
thicknessof the member,providedthat the concrete
canbeplacedwithoutdifficultyso as tosurroundall
reinforcementthoroughlyand fill the comers of the
form,For mostwork,20 nun
alareaateissuitable.
Wherethere is norestrictionto theflow ofconcrete
intosections,40 nun orlaraorsizemaybepermitted.
Inconcreteelementswiththinsections,closelyspaced
reinforcementor small
cover,considerationshouldbe
liven to the
useof 10mmnominalmaximumlize.
Plumsabove 160 nun anduptoanyreuonableaize
maybeusedinplainconcreteworkup to amaximum
limit of 20 percentbyvolumeofconcrete when
specificallypermittedbytheenaineer-in-charao.The
plumsshallbedistributedevenlyandIhallbenotcloser
than 1'0mm fromthe lurface.
5.3.3.1Forheav.iJyreinforcedconcretemembenu
in theelseof ribsof main beams,the nominal
maximum
aizeof the
a'lf'lateIhould usuallybe
re.trietedto~mmlei.thantheminimumcleareli.tanee
betweenthemainbarsorSmmlellthantheminimum
cover to thereinforcementwhicheveri.Imaller.
5.3.4 Coarse and finealsrelateIhallbe batched
separately.All.in-alar.,ltemaybeusedonlywhere
lpecificallypermittedbythoenlineer-in-char,e.
1.4Water
.Waterused formixin,and cunn'lhallbeclean and
14
freefrominjuriousamountsofoils.acids,alkalis,salta,
sugar,organicmaterialsor othersubstancesthat may
bedeleterioustoconcreteor steel.
Potablewater isgenerallyconsidered satisfactory
formixinaconcrete.As a guide thefollowing
concentrationsrepresent themaximumpennissible
values:
a) Toneutralize100 ml sample of water,usir.1
phenolphthaleinas anindicator,it should not
require morethan'mlof0.02nonnal NaOH.
The details oftestareaiven in 8.1ofIS
3025(Part 22).
b) Toneutralize100 ml sample of water,uains
mixedindicator, itshouldnotrequiremore
than2'ml of 0.02nonnalH
2SO
•.The details
oftestshall beasgivenin 8ofIS3025
(Part 23).
c)Permissiblelimits forsolids shallbeasliven
inTable1.
5.4.1 Incaseofdoubtregardinl development of
strength.the suitabilityof waterformakingconcrete
shallbeascertainedbythecompressivestreolthand
initialsettingtimetestsspecifiedin5.4.1.1and5.4.1.3.
5.4.1.1Thesample of watertakenforteslin,Ihall
representthewater proposedtobeusedforconcreting,
dueaccountbeingpaidtoseasonalvariation.The
sampleshall notreceive anytreatmentbefore te_un,
otherthanthatenvisagedintheregularsupplyofwater
proposedforuseinconcrete.Thesampleshallbeltored
in acleancontainerprevio~lly rinsedoutwithlimilar
water.
5.4.1.2Averalo 28 dayscompressiveItten.thof at
least
three
l~Onunconcretecubespreparedwithwater
proposedto beusedshall notbelellthan90percent
of the
averageof
strenlthofthreesimilar concrete
cubes
preparedwithdiltilledwater,Th.
cube••hall
beprepared.curedand testedinaccordancewiththe
requirementsof IS516.
5.4.1.3 Theinitial••ttinltimeofte.tblockmadewith
theappropriatecementandthewaterpropolldtobe
used.hallnotbele••than30 min and.hallnotdlff.
by±30min fromthe initial.etlinatime of control
teltblockpreparedwiththelamecement,anddiltiJled
water.Theteltblock.,hanbepreparedandtiltedIn
accordancewiththerequirementaof IS4031(P.n5).
5.4.1ThepH valueof water,hallbenotlellthan 6.
5.4.3Sea Water
Mixinl or curin, ofconcretewith.eawalerilnot
recommendedbecause'ofPf"Onceofharmful.lltlin
...water.UnderunavoidableCircumltaneel1Mwater
maybeusedformixin.orcuriolinplainconcretewith
noembeddedsteelafterhayiJlllivendueconllderation
toposlible.disadvantapaandprecaution.includin,UII
ofappropriatecementsystem.
IS 456 : 2000
Table1PermissibleLimitforSolids
tCtaus«5.4)
51
Nil,
n
ii)
iii)
iv)
v)
Organic
Inorganic
Sulphates(asSO)
Chlorides(asCIl
Suspendedmailer
'Iesred asper
IS~02~(Part IS)
IS~025(PurtIll)
IS~02'i(Part24)
IS.1025(Part~2)
IS3025(Part 17)
l'crDli~~ible Limit,
Mllx
2001ll!!!1
11M10mg!1
400 mg/l
2IM)()IIIg!1
forconcrete1101coutaining
embedded steeland~(JO1IIg/\
I<Jrreinforcedconcretework
20001lIg11
5.4.4Water foundsatisfactoryformixingisalso
suitableforcuringconcrete.However, water used for
curingshouldnotproduceanyobjectionablestainor
unsightly deposit\10the concretesurface.The presence
of tannicaddor ironcompoundsisobjectionable,
5.5Admixtures
5.5.1Admixture. if used shall comply withIS9103.
Previousexperiencewith anddata(IIisuchmaterials
shouldheconsidered in relationtothe likelystandardsof
supervision
andworkmanshipto thework
beingspecified.
5.5.2Admixturesshouldnotimpair durability(If
concretenorcombinewith theconstituentto form
harmfulcompoundsnor increasetheriskofcorrosion
ofreinforcement.
5.5.3Theworkability,compressivestrengthandthe
slumplossofconcretewith and without the usc of
admixturesshall be
established duringthetrialmixes
beforeliseof
admixtures
5.5.4The relative densityofliquid admixtures shall
hecheckedforcadidrumcontainingadmixtures and
comparedwithtill'specifiedvaluebeforeacceptance.
5.5.5Thechloridecontentofadmixturesshall
be
independently
testedfilleachhutcl)before
acceptance.
5.5,6Iftwoormoreadmixturesart'used
simultaneouslyin the same concrete mix.Jalashould
beobtainedto assess their interactionandto ensure
their
compatibility,
5.6Reinforcement
TIll'reinforcementshallbeanyofthe following:
a)Mildsteelandmediumtensilesteelbars
conformingto IS432(Part I).
h) High strength deformedsteelbarsconforming
toIS1786.
c)Hard-drawnsteel wire fabricconforming to
IS 1566.
d)StructuralsteelconformingtoGrade Aof
IS 2062.
5.6.1 Allreinforcementshall he free from loose mill
scales.loose rustandcoatsofpaints. oil. mudorany
othersubstances which maydestroyorreducehondo
Sand blasting or other treatment isrecommendedto
deanreinforcement.
5.6.2Specialprecautions likecoating(Ifreinforcement
mayberequiredforreinforcedconcrete clcmenIsin
exceptionalcasesand forrehabilitationof structures.
Specialistliteraturemayhereferredto insuchcases.
5.6.3 The modulusofelasticityof steel shall be taken
as200kN/l1llJ1·~. Thecharacteristicyield strength of
differentsteelshallbeassumedas the minimum yield
stress/0.2 percentproofstressspecifiedin the relevant
IndianStandard.
13.7Storageof'Materials
Storageof materials shallheasdescribed in IS40K2.
6CONCRETE
6.1Grades
Theconcreteshallbeingradesdesignatedas per
Tanlc2
6.1.1Thecharacteristicstrengthisdefinedasthe
strengthofmaterialbelow whichnotmorethan
5percentofthetest results arcexpectedto fall.
6.1.2Tileminimumgradeofconcreteforplainand
reinforcedconcreteshall beasperTable5.
6.1.3Concreteofgradeslowerthanthosegivenin
Table5mayheusedfor plain concreteconstructions.
lean
concrete,SImplefoundations,foundationfor
masonry
wallsandothersimpleortcmporury
reinforcedconcreteconstruction.
6.2PropertiesofConcrete
6.2.1IIIClI'(/.I'(,ofStrengthwith Agi'
There is normallyagainofstrengthbeyond2Sdays.
Thequantumofincreasedependsupon the)!radcand
typeofcement,curingandcnvuoruucnralconditions,
etc.Thedesign should1)('h:1S,xlon2xdav-, charac
tcristic strength"fcom.r. "'lIlkssthere is a evidenceIII
15
Table1PermissibleLimitforSolids
tCtaus«5.4)
51
Nil,
n
ii)
iii)
iv)
v)
Organic
Inorganic
Sulphates(asSO)
Chlorides(asCIl
Suspendedmailer
'Iesred asper
IS~02~(Part IS)
IS~025(PurtIll)
IS~02'i(Part24)
IS.1025(Part~2)
IS3025(Part 17)
l'crDli~~ible Limit,
Mllx
2001ll!!!1
11M10mg!1
400 mg/l
2IM)()IIIg!1
forconcrete1101coutaining
embedded steeland~(JO1IIg/\
I<Jrreinforcedconcretework
20001lIg11
5.4.4Water foundsatisfactoryformixingisalso
suitableforcuringconcrete.However, water used for
curingshouldnotproduceanyobjectionablestainor
unsightly deposit\10the concretesurface.The presence
of tannicaddor ironcompoundsisobjectionable,
5.5Admixtures
5.5.1Admixture. if used shall comply withIS9103.
Previousexperiencewith anddata(IIisuchmaterials
shouldheconsidered in relationtothe likelystandardsof
supervision
andworkmanshipto thework
beingspecified.
5.5.2Admixturesshouldnotimpair durability(If
concretenorcombinewith theconstituentto form
harmfulcompoundsnor increasetheriskofcorrosion
ofreinforcement.
5.5.3Theworkability,compressivestrengthandthe
slumplossofconcretewith and without the usc of
admixturesshall be
established duringthetrialmixes
beforeliseof
admixtures
5.5.4The relative densityofliquid admixtures shall
hecheckedforcadidrumcontainingadmixtures and
comparedwithtill'specifiedvaluebeforeacceptance.
5.5.5Thechloridecontentofadmixturesshall
be
independently
testedfilleachhutcl)before
acceptance.
5.5,6Iftwoormoreadmixturesart'used
simultaneouslyin the same concrete mix.Jalashould
beobtainedto assess their interactionandto ensure
their
compatibility,
5.6Reinforcement
TIll'reinforcementshallbeanyofthe following:
a)Mildsteelandmediumtensilesteelbars
conformingto IS432(Part I).
h) High strength deformedsteelbarsconforming
toIS1786.
c)Hard-drawnsteel wire fabricconforming to
IS 1566.
d)StructuralsteelconformingtoGrade Aof
IS 2062.
5.6.1 Allreinforcementshall he free from loose mill
scales.loose rustandcoatsofpaints. oil. mudorany
othersubstances which maydestroyorreducehondo
Sand blasting or other treatment isrecommendedto
deanreinforcement.
5.6.2Specialprecautions likecoating(Ifreinforcement
mayberequiredforreinforcedconcrete clcmenIsin
exceptionalcasesand forrehabilitationof structures.
Specialistliteraturemayhereferredto insuchcases.
5.6.3 The modulusofelasticityof steel shall be taken
as200kN/l1llJ1·~. Thecharacteristicyield strength of
differentsteelshallbeassumedas the minimum yield
stress/0.2 percentproofstressspecifiedin the relevant
IndianStandard.
13.7Storageof'Materials
Storageof materials shallheasdescribed in IS40K2.
6CONCRETE
6.1Grades
Theconcreteshallbeingradesdesignatedas per
Tanlc2
6.1.1Thecharacteristicstrengthisdefinedasthe
strengthofmaterialbelow whichnotmorethan
5percentofthetest results arcexpectedto fall.
6.1.2Tileminimumgradeofconcreteforplainand
reinforcedconcreteshall beasperTable5.
6.1.3Concreteofgradeslowerthanthosegivenin
Table5mayheusedfor plain concreteconstructions.
lean
concrete,SImplefoundations,foundationfor
masonry
wallsandothersimpleortcmporury
reinforcedconcreteconstruction.
6.2PropertiesofConcrete
6.2.1IIIClI'(/.I'(,ofStrengthwith Agi'
There is normallyagainofstrengthbeyond2Sdays.
Thequantumofincreasedependsupon the)!radcand
typeofcement,curingandcnvuoruucnralconditions,
etc.Thedesign should1)('h:1S,xlon2xdav-, charac
tcristic strength"fcom.r. "'lIlkssthere is a evidenceIII
15
IS456:1000
'Dable2 GndesofConcnte
(Clause6.1.9.2.2.15.1.1and36.1)
NOTES
I InthedesipotionofconcretemixMreferstothemixlUldthe
numberto thespecifiedcompnlUiveItrenathof150mm size
cubelit28days.expressedinN/mmJ.
1Forconcreteofcom~ssive strenathareaterthanM55.desip
parametersgiveninthellalldllrdmaynotbeapplicableandthe
values may be obtained from specializedliteraturesand
experimcntalresults.
justifya higherstrengthforaparticularstructuredueto
age.
6.2.1.1Forconcreteof gradeM 30andabove.the
rateofincreaseofcompressivestrengthwithageshall
be basedon actualinvestigations.
6.2.1.2
Wheremembers
aresubjectedto lowerdirect
loadduringconstruction,they shouldbe checkedfor
stressesresultingfromcombinationof directloadand
bendingduringconstruction.
6.2.2TensileStrengthofConcrete
Theflexuralandsplittingtensilestrengthsshall be
obtainedasdescribedin IS516and IS5816
respectively.When the designerwishesto use an
estimateof the tensilestrengthfromthecompressive
strength,the followingformulamaybeused:
Flexuralstrength,fer=0.7..[l;N/mm
2
wheref",isthecharacteristiccubecompressivestrength
of concreteinN/mm
2
•
6.2.3ElasticDeformation
Themodulusofelasticityisprimarilyinfluencedby
the elasticpropertiesof theaggregateandtoa lesser
extent by the conditions of curingavetage of the
concrete,the mixproportions
andthe
typeofcement.
Themodulusofelasticityis normallyrelatedtothe
compressivestrengthofconcrete.
6.2.3.1Themodulusofelasticityofconcretecan be
assumedas
follows:
..1
CreepCoefficient
2.2
1.6
1.1
CoefficientofThermal
.ExpansionforConcrrte/"C
1.2 to 1.3x10'5
0.9to1.2x10"
. 0.7to0.95x10"
0.8to0.95x10"
0.6lQ,.o.9x10'5
AgeatLoading
7 days
28days
Iyear
Quartzite
Sandstone
Granite
Basalt
Limestone
TypeofAggregate
NOTE-Theultill1llecreep1UIin.eatimlledas describedabove
doesnotincludetheelasticIItI'lIin.
6.2.6ThermalExpansion
ThecoefficientofthermalexpansiondependsonIllltUI'e
of cement, theaggregate,.the cementcontent,the
relative
humidityand the
sizeofsections.The value
ofcoefficientof
thermalexpansionfor
concretewith
differentaggregatesmaybetakenasbelow:
where
E
c
istheshort tenn staticmodulusof elasticityin
N/mm
2
•
Actualmeasuredvaluesmay differ by
±20percent
fromthe
valuesobtainedfromthe aboveexpression.
6.2.4Shrinlcage
The total shrinkage of concretedepeRdsuponthe
constituents ofconcrete,size of the member and
environmentalconditions.For a givenhumidityand
temperature,the totalshrinkageof
concreteis most
influencedbythe total
amountof water
presentinthe
concreteatthetimeof mixingand,to alesserextent,
by thecementcontent.
6.2.4.1In the
absenceof
testdata, theapproximate
valueof the total
shrinkagestrain for
deslanmaybe
takenas 0.0003 (formoreinfonnation,seeIS1343).
6.2.SCrtepofConcrete
Creepofconcretedepends,inadditiontothefactors
listed in 6.2.4, on the stress in theconcrete.ageat
loadingand thedurationofleading.Aslongasthe
stress in concrete does not exceed one-third of its
characteristiccompressivestrength, creep maybe
assumedto beproportionalto thestress.
6.1.5.1Intheabsenceofexperimentaldataanddetailed
informationontheeffectof thevariables,theultimate
creep strain may be estimated from the following
valuesofcreepcoefficient(thatis.ultimate
creepstrain!
elastic strain at theageofloading);for long span
structure,it is advisable to determine actual creep
strain,likelyto take
place:
2S
30
3S
40
45
SO
SS
60
65
70
75
80
M2S
M30
M3S
M40M4S
MSO
MSS
M60
M6S
M70
M7S
M80
GradeDeI.....IIOIlSpedftedCba 1Ie
eo.,...."S til
ISOamiCubeat210.,."
Nlmm2
(2) (3)
M 10 10
MIS IS
M20 20
Hi,h
Strength
Concrete
(I)
Ordinary
Concrete
Slalldllrd
Concrete
Group
"'."
16
'Dable2 GndesofConcnte
(Clause6.1.9.2.2.15.1.1and36.1)
NOTES
I InthedesipotionofconcretemixMreferstothemixlUldthe
numberto thespecifiedcompnlUiveItrenathof150mm size
cubelit28days.expressedinN/mmJ.
1Forconcreteofcom~ssive strenathareaterthanM55.desip
parametersgiveninthellalldllrdmaynotbeapplicableandthe
values may be obtained from specializedliteraturesand
experimcntalresults.
justifya higherstrengthforaparticularstructuredueto
age.
6.2.1.1Forconcreteof gradeM 30andabove.the
rateofincreaseofcompressivestrengthwithageshall
be basedon actualinvestigations.
6.2.1.2
Wheremembers
aresubjectedto lowerdirect
loadduringconstruction,they shouldbe checkedfor
stressesresultingfromcombinationof directloadand
bendingduringconstruction.
6.2.2TensileStrengthofConcrete
Theflexuralandsplittingtensilestrengthsshall be
obtainedasdescribedin IS516and IS5816
respectively.When the designerwishesto use an
estimateof the tensilestrengthfromthecompressive
strength,the followingformulamaybeused:
Flexuralstrength,fer=0.7..[l;N/mm
2
wheref",isthecharacteristiccubecompressivestrength
of concreteinN/mm
2
•
6.2.3ElasticDeformation
Themodulusofelasticityisprimarilyinfluencedby
the elasticpropertiesof theaggregateandtoa lesser
extent by the conditions of curingavetage of the
concrete,the mixproportions
andthe
typeofcement.
Themodulusofelasticityis normallyrelatedtothe
compressivestrengthofconcrete.
6.2.3.1Themodulusofelasticityofconcretecan be
assumedas
follows:
..1
CreepCoefficient
2.2
1.6
1.1
CoefficientofThermal
.ExpansionforConcrrte/"C
1.2 to 1.3x10'5
0.9to1.2x10"
. 0.7to0.95x10"
0.8to0.95x10"
0.6lQ,.o.9x10'5
AgeatLoading
7 days
28days
Iyear
Quartzite
Sandstone
Granite
Basalt
Limestone
TypeofAggregate
NOTE-Theultill1llecreep1UIin.eatimlledas describedabove
doesnotincludetheelasticIItI'lIin.
6.2.6ThermalExpansion
ThecoefficientofthermalexpansiondependsonIllltUI'e
of cement, theaggregate,.the cementcontent,the
relative
humidityand the
sizeofsections.The value
ofcoefficientof
thermalexpansionfor
concretewith
differentaggregatesmaybetakenasbelow:
where
E
c
istheshort tenn staticmodulusof elasticityin
N/mm
2
•
Actualmeasuredvaluesmay differ by
±20percent
fromthe
valuesobtainedfromthe aboveexpression.
6.2.4Shrinlcage
The total shrinkage of concretedepeRdsuponthe
constituents ofconcrete,size of the member and
environmentalconditions.For a givenhumidityand
temperature,the totalshrinkageof
concreteis most
influencedbythe total
amountof water
presentinthe
concreteatthetimeof mixingand,to alesserextent,
by thecementcontent.
6.2.4.1In the
absenceof
testdata, theapproximate
valueof the total
shrinkagestrain for
deslanmaybe
takenas 0.0003 (formoreinfonnation,seeIS1343).
6.2.SCrtepofConcrete
Creepofconcretedepends,inadditiontothefactors
listed in 6.2.4, on the stress in theconcrete.ageat
loadingand thedurationofleading.Aslongasthe
stress in concrete does not exceed one-third of its
characteristiccompressivestrength, creep maybe
assumedto beproportionalto thestress.
6.1.5.1Intheabsenceofexperimentaldataanddetailed
informationontheeffectof thevariables,theultimate
creep strain may be estimated from the following
valuesofcreepcoefficient(thatis.ultimate
creepstrain!
elastic strain at theageofloading);for long span
structure,it is advisable to determine actual creep
strain,likelyto take
place:
2S
30
3S
40
45
SO
SS
60
65
70
75
80
M2S
M30
M3S
M40M4S
MSO
MSS
M60
M6S
M70
M7S
M80
GradeDeI.....IIOIlSpedftedCba 1Ie
eo.,...."S til
ISOamiCubeat210.,."
Nlmm2
(2) (3)
M 10 10
MIS IS
M20 20
Hi,h
Strength
Concrete
(I)
Ordinary
Concrete
Slalldllrd
Concrete
Group
"'."
16
7WORKABILITY OFCONCRETE
7.1 The concrete mix proportions chosen should be
such that the concrete is of
adequateworkabilityfor
the placingconditionsof the concreteandcan properly
IS456:2000
becompacted with the means available. Suggested
rangesofworkabihtyofconcretemeasuredin
accordance with IS
J199are given below:
Degreeoj· SlumpWorkllbility (mm)
(2) (3)
Very lowSee7.J.l
Low 25-75
PlacingConditions
(I)
Blindingconcrete;
Shallow sections;
Pavements using pavers
Mass concrete:
Lightlyreinforced
sections in
slabs,
beams,walls,columns:
Floors;
Hand placed pavements;
Canallining;
Strip
footings
Heavily reinforced
sectionsinslabs.
beams,walls.columns;
Slipform
work;
Pumpedconcrete
Trench fill;
In-situpiling .
Trernieconcrete
Medium
Iligh
Veryhigh
50-100
75-100
100-150
See 7.1.2
NOTE-Formostofthe
placingconditions,mtcrnulvibrators(needlevihrators)aresuitable.Thediameteroftheneedleshall be
determinedbased on thedensityandspacingofreinforcementbarsandthicknessofsections.Furtremieconcrete,vibratorsarenot
required tobeused(s,ealso l:t~~).
7.1.1 In the'verylow' categoryofworkabilitywhere
strict control isnecessary,for example pavement
qualityconcrete,measurementof workability
hy
determinationofcompacting
factorwillhe more
appropriate than
slump
(seeIS 1199) and a value of
compacting factor of0.75 to0.80issuggested.
7.1.2 In the'very high'categoryof workability,
measurementof workability hy determinationof flow
will beappropriate(seeIS9103).
8DURABILITY OFCONCRETE
8.1.General
Adurableconcreteis one that performs satisfactorily
in theworking environmentduring itsanticipated
exposure conditions
duringservice. The materialsand
mix proportions specified and used should be such as
to maintain itsintegrity and,ifapplicable, to protect
embedded metal from corrosion.
8.1.1One of the main characteristics influencing the
durabilityof concrete is its permeabilityto the ingress
ofwater,oxygen,carbondioxide.chloride,sulphateand
otherpotentiallydeleterioussubstances.Impermeability
isgovernedbytheconstituentsandworkmanshipused
inmakingtheconcrete.Withnormal-weightaggregates
2116818/07-4..
17
a
suitablylowpermeabilityis achieved byhaving an
adequatecementcontentsufficientlylow freewater/
cement ratio,
byensuring complete compaction of the
concrete. andbyadequatecuring.
The factors influencing durability include:
a)theenvironment;
h) thecover toembeddedsteel;
c) thetypeandqualityofconstituentmaterials;
d) the cementcontent and water/cement ratio of
the concrete;
e) workmanship, to obtain fullcompactionand
efficient curing; and
f)the shape andsizeof the member.
The
degreeofexposure anticipated for the concrete
during itsservicelifetogetherwithotherrelevant
factors relating to mix composition. workmanship.
designanddetailing
shouldbeconsidered.The
concretemixto provideadequatedurabilityunderthese
conditions should be.chosen taking account of the
accuracy of current testing regimes for control and
complianceasdescribedin thisstandard.
7.1 The concrete mix proportions chosen should be
such that the concrete is of
adequateworkabilityfor
the placingconditionsof the concreteandcan properly
IS456:2000
becompacted with the means available. Suggested
rangesofworkabihtyofconcretemeasuredin
accordance with IS
J199are given below:
Degreeoj· SlumpWorkllbility (mm)
(2) (3)
Very lowSee7.J.l
Low 25-75
PlacingConditions
(I)
Blindingconcrete;
Shallow sections;
Pavements using pavers
Mass concrete:
Lightlyreinforced
sections in
slabs,
beams,walls,columns:
Floors;
Hand placed pavements;
Canallining;
Strip
footings
Heavily reinforced
sectionsinslabs.
beams,walls.columns;
Slipform
work;
Pumpedconcrete
Trench fill;
In-situpiling .
Trernieconcrete
Medium
Iligh
Veryhigh
50-100
75-100
100-150
See 7.1.2
NOTE-Formostofthe
placingconditions,mtcrnulvibrators(needlevihrators)aresuitable.Thediameteroftheneedleshall be
determinedbased on thedensityandspacingofreinforcementbarsandthicknessofsections.Furtremieconcrete,vibratorsarenot
required tobeused(s,ealso l:t~~).
7.1.1 In the'verylow' categoryofworkabilitywhere
strict control isnecessary,for example pavement
qualityconcrete,measurementof workability
hy
determinationofcompacting
factorwillhe more
appropriate than
slump
(seeIS 1199) and a value of
compacting factor of0.75 to0.80issuggested.
7.1.2 In the'very high'categoryof workability,
measurementof workability hy determinationof flow
will beappropriate(seeIS9103).
8DURABILITY OFCONCRETE
8.1.General
Adurableconcreteis one that performs satisfactorily
in theworking environmentduring itsanticipated
exposure conditions
duringservice. The materialsand
mix proportions specified and used should be such as
to maintain itsintegrity and,ifapplicable, to protect
embedded metal from corrosion.
8.1.1One of the main characteristics influencing the
durabilityof concrete is its permeabilityto the ingress
ofwater,oxygen,carbondioxide.chloride,sulphateand
otherpotentiallydeleterioussubstances.Impermeability
isgovernedbytheconstituentsandworkmanshipused
inmakingtheconcrete.Withnormal-weightaggregates
2116818/07-4..
17
a
suitablylowpermeabilityis achieved byhaving an
adequatecementcontentsufficientlylow freewater/
cement ratio,
byensuring complete compaction of the
concrete. andbyadequatecuring.
The factors influencing durability include:
a)theenvironment;
h) thecover toembeddedsteel;
c) thetypeandqualityofconstituentmaterials;
d) the cementcontent and water/cement ratio of
the concrete;
e) workmanship, to obtain fullcompactionand
efficient curing; and
f)the shape andsizeof the member.
The
degreeofexposure anticipated for the concrete
during itsservicelifetogetherwithotherrelevant
factors relating to mix composition. workmanship.
designanddetailing
shouldbeconsidered.The
concretemixto provideadequatedurabilityunderthese
conditions should be.chosen taking account of the
accuracy of current testing regimes for control and
complianceasdescribedin thisstandard.
IS456:2000
.
Table 3Environmental ExposureConditions
(Clauses8.2.2.1and35.3.2)
i) Mild Concrete surfacesprotectedagainst
weatheroraggressiveconditions,except
thosesituatedinccestalarea.
ii)Moderate Concretesurfacesshelteredfromsevere
rainorfreezingwhilstwet
Concreteexposedtocondensational'dmin
Concretecontinuouslyunderwater
Concreteincontactorbt!riedundernon
aggressivesoil/ground\Yater
Concretesurfacesshelteredfrom
saturatedsaltairincoastalarea
iii)Severe Concretesurfacesexposed to severe
rain,alternatewettinland drying or
occasionalfreezingwhilstwet orsevere
condensation.
Concrete~letely immersedinseawater
Concl1'tcexposedtocoosualenvironment
iv) VerysevereCOncrelCsurfacesexposedtoseawater
spray.corrosivefumesorseverefreezin,
conditionswhilstwet
Concrete in contactwitbor buried
underaaressivelub-loiVaroundwater
v) Extreme Surfaceofmembersintidalzone
Membenindirectcontactwith liquldl
solidaggressivechemicals
8.2Requirementsfor DurabUity
8.2.1Shapeand SizeofMember
The shape or design details of exposed structures
should
besuch as to promote good drainage ofwater
and to avoid
standingpoolsandrundownofwater.
Care should alsobetakento minimizeanycracks that
may collectortransmitwater.Adequate curingis
essential to
avoidtheharmfuleffects of earlylossof
rnoisture(see13.5).Memberprofilesandtheir
intersectionswithothermembersshallbedesignedand
detailedinawaytoensureeasyflow of concreteand
proper compaction duringconcreting.
Concreteis morevulnerableto deteriorationdue to
chemicalorclimaticattack whenitis inthinsections,
in sections under
hydrostaticpressure from one side
only,inpartiallyimmersedsectionsand
Atcomersand
edges ofelements.The life of the structure canbe
lengthenedbyprovidingextracover tosteel,by
chamfering the corners orbyusing circular cross
sections
orbyusingsurfacecoatings whichpreventor
reduce the ingress of water, carbon dioxide or
aggressivechemicals,
8.2.2ExposureConditions
8.2.2.1Generalenvironment
Thegeneralenvironmentto whichtheconcretewill
be exposed during its working life is classified into
five
levelsof severity,thatis, mild,moderate,
severe,
verysevereandextremeasdescribedin Table3.
The freewater-cement ratiois animportantfactor in
governingthedurabilityofconcreteandshouldalways
bethelowestvalue.Appropriatevaluesfor minimum
cementcontentand themaximumfreeweler-cemenl
ratio are given in TableSfordifferent exposure
conditions.The minimumcementcontentand
maximumwater-cementratioapplyto 20mm nominal
maximum
sizeaggresate.Forothersizesofaggregate
theyshouldbechanged81givenin Table6.
S±l
4±t
EntrainedAir
Percentage
NominalMaximumSize
Aggregate
(mm)
20
40
Since airentrainmentreducesthestrength,suitable
adjustmentsmay be made in the mix design for
achievingrequired strength.
8.1.1.4Exposuretosulphateattack
Table4givesrecommendationsforthetypeofcement,
maximumfree water/cement ratio and minimum
cement content, which are requiredatdifferentsulphate
concentrationsin near-neutralgroundwaterhaving
pHof6to 9.
For theveryhighsulphateconcentrationsin ClassS
conditions,someformof liningsuchaspolyethylene
orpolychloroprenesheet;orsurface coating based on
asphalt,chlorinatedrubber,epoxy; orpolyurethane
materialsshouldalsobe usedtopreventaccess bythe
sulphatesolution.
8.2.3RequirementofConcreteCover
8.1.3.1Theprotectionof thesteelin concreteagainst
corrosiondependsuponanadequatethicknessofgood
qualityconcrete.
8.2.3.2Thenominalcoverto thereinforcementshall
beprovidedas per26.4.
8.%.4ConcreteMixProportions
8.1.4.1General
8.2.2.2Abrasive
Specialistliteraturesmaybereferredto fordurability
requirementsofconcretesurfacesexposedtoabrasive
action,forexample,incaseofmachineryandmetalt)'fes.
8.2.2.3Freezingandthawing
Where freezing and thawingactionsunderwet
conditionsexist.enhanceddurabilitycanbeobtained
bytheuseofsuitableairentrainingadmixtures.When
concretelower than grade M 50 is used under these
conditions,the mean total air
contentbyvolumeof
the
fresh concreteat the time of delivery into the
construction
should be:
ExposureConditions
(3)
SINo.Environment
(1) (2)
18
.
Table 3Environmental ExposureConditions
(Clauses8.2.2.1and35.3.2)
i) Mild Concrete surfacesprotectedagainst
weatheroraggressiveconditions,except
thosesituatedinccestalarea.
ii)Moderate Concretesurfacesshelteredfromsevere
rainorfreezingwhilstwet
Concreteexposedtocondensational'dmin
Concretecontinuouslyunderwater
Concreteincontactorbt!riedundernon
aggressivesoil/ground\Yater
Concretesurfacesshelteredfrom
saturatedsaltairincoastalarea
iii)Severe Concretesurfacesexposed to severe
rain,alternatewettinland drying or
occasionalfreezingwhilstwet orsevere
condensation.
Concrete~letely immersedinseawater
Concl1'tcexposedtocoosualenvironment
iv) VerysevereCOncrelCsurfacesexposedtoseawater
spray.corrosivefumesorseverefreezin,
conditionswhilstwet
Concrete in contactwitbor buried
underaaressivelub-loiVaroundwater
v) Extreme Surfaceofmembersintidalzone
Membenindirectcontactwith liquldl
solidaggressivechemicals
8.2Requirementsfor DurabUity
8.2.1Shapeand SizeofMember
The shape or design details of exposed structures
should
besuch as to promote good drainage ofwater
and to avoid
standingpoolsandrundownofwater.
Care should alsobetakento minimizeanycracks that
may collectortransmitwater.Adequate curingis
essential to
avoidtheharmfuleffects of earlylossof
rnoisture(see13.5).Memberprofilesandtheir
intersectionswithothermembersshallbedesignedand
detailedinawaytoensureeasyflow of concreteand
proper compaction duringconcreting.
Concreteis morevulnerableto deteriorationdue to
chemicalorclimaticattack whenitis inthinsections,
in sections under
hydrostaticpressure from one side
only,inpartiallyimmersedsectionsand
Atcomersand
edges ofelements.The life of the structure canbe
lengthenedbyprovidingextracover tosteel,by
chamfering the corners orbyusing circular cross
sections
orbyusingsurfacecoatings whichpreventor
reduce the ingress of water, carbon dioxide or
aggressivechemicals,
8.2.2ExposureConditions
8.2.2.1Generalenvironment
Thegeneralenvironmentto whichtheconcretewill
be exposed during its working life is classified into
five
levelsof severity,thatis, mild,moderate,
severe,
verysevereandextremeasdescribedin Table3.
The freewater-cement ratiois animportantfactor in
governingthedurabilityofconcreteandshouldalways
bethelowestvalue.Appropriatevaluesfor minimum
cementcontentand themaximumfreeweler-cemenl
ratio are given in TableSfordifferent exposure
conditions.The minimumcementcontentand
maximumwater-cementratioapplyto 20mm nominal
maximum
sizeaggresate.Forothersizesofaggregate
theyshouldbechanged81givenin Table6.
S±l
4±t
EntrainedAir
Percentage
NominalMaximumSize
Aggregate
(mm)
20
40
Since airentrainmentreducesthestrength,suitable
adjustmentsmay be made in the mix design for
achievingrequired strength.
8.1.1.4Exposuretosulphateattack
Table4givesrecommendationsforthetypeofcement,
maximumfree water/cement ratio and minimum
cement content, which are requiredatdifferentsulphate
concentrationsin near-neutralgroundwaterhaving
pHof6to 9.
For theveryhighsulphateconcentrationsin ClassS
conditions,someformof liningsuchaspolyethylene
orpolychloroprenesheet;orsurface coating based on
asphalt,chlorinatedrubber,epoxy; orpolyurethane
materialsshouldalsobe usedtopreventaccess bythe
sulphatesolution.
8.2.3RequirementofConcreteCover
8.1.3.1Theprotectionof thesteelin concreteagainst
corrosiondependsuponanadequatethicknessofgood
qualityconcrete.
8.2.3.2Thenominalcoverto thereinforcementshall
beprovidedas per26.4.
8.%.4ConcreteMixProportions
8.1.4.1General
8.2.2.2Abrasive
Specialistliteraturesmaybereferredto fordurability
requirementsofconcretesurfacesexposedtoabrasive
action,forexample,incaseofmachineryandmetalt)'fes.
8.2.2.3Freezingandthawing
Where freezing and thawingactionsunderwet
conditionsexist.enhanceddurabilitycanbeobtained
bytheuseofsuitableairentrainingadmixtures.When
concretelower than grade M 50 is used under these
conditions,the mean total air
contentbyvolumeof
the
fresh concreteat the time of delivery into the
construction
should be:
ExposureConditions
(3)
SINo.Environment
(1) (2)
18
8.2.4.2Maximumcementcontent
Cement content not includingflyash and ground
granulated blast furnace slag inexcessof 450kglm
l
should not be usedunlessspecialconsiderationhas
IS456:2000
been given in design to the increased riskofcracking
due to
dryingshrinkage in.thin sections, or to early
thermalcracking andto theincreasedrisk of
damage
duetoalkalisilicareactions.
Table 4RequirementsforConcreteExposed toSulphateAttack
(Clauses8.2.2.4and9.1.2)
Percent gil gil
(I)(2) (3.) (4) (5)
1) Traces LessthanLessthan
«0.2) 1.0 n.3
ConcentrationofSuJpbates,
ExpresseduSOJ
....
SI
No.
ClaVi
... 1..-~oil,
TotalSOl SOlin
2:1Water:
SoilExtract
InGround
Water
Typeof Cement
(6)
Ordinary Portland
cement or Portland
slag cement or
Portlandpozzolana
cement
Dense,ruDyCompactedConcrete.
Made wltb 20 mmNominal
Maximum SizeAllre.ate.
ComplyIDlwitbIS383
# ,
Minimum Maximum
Cement FaceWater-
Content Cement
kllm
J
Ratio
(7) (8)
280 0.5S
iv)4 10to 11[0 2.5to
2.0 S,O 50
v) 5 Morethin MorechanMorethan
2.0 5.0 5.0
ii)
iii)
2 0.2 to
0.5
0.5
to
1.0
1.0to
1.9
1.91U
3.1
0.3to
1.2
1.110
2.5
Ordinary Portland
cement or
Portlandslag
cementor
Portland
pozzolanacement
Supersulphated
cement or
sulphateresisting
Portlandcement
Supersulphated
cement or
sulphateresisting
Portland cement
Portlandpozzolana
cement or Portland
slag cement
Supersulphatcd
or sulphate
resisting
Portland
cement
Sulphateresisting,.
Portlandcementor
supersulphatedc;eanent
withprotectivecoatings
330
310
330
350
370
4(X)
0.50
o.so
0.50
0.45
O,4S
0.40
NOTES
1 Cement content given in this tableisIrrespectiveofgradesofcement.
2Use of supersulphatedcement isgenerallyrestrictedwheretheprevailingtemperatureisabove40f'C.
3Supersutpbated cementgivesanacceptable life providedthatthe concrete is dense andpreparedwithawater-cementratio of 0.4 or
less, inmineralacids,down topH3.~.
4 Thecementcontents given incol6 ofthistablearetheminimum recommended. ForSO,contentsneartheupperlimit ofanyclass.
cement contents above theseminimumareadvised.
5 For severeconditions.such ~thinsectionsunderhydrostaticpressureononeside onlyandsectionspantyimmersed.considerations
should
begiven to
afurther reduction ofwater-cementratio.
6PortlandslagcementconformingtoIS45.5withslagcontentmorethan50percentexhibitsbettersulphateresisting properties.
7 Where chl()ride is encountered alongwith sulphates in soilorgroundwater.ordinaryPortlandcement with C1Acontentfrom~to8
percent shall
bedesirable to
heused in concrete,insteadof sulphateresistingcement.Alternatively.Portland ~lllgermentconforming
to IS4~~havingmorethan~opercentslagOfa blendofordinaryPortlandcementandslagmaybeused providedsutlicient information
is available on
performanceof.
suchblended cements intheseconditions.
19
Cement content not includingflyash and ground
granulated blast furnace slag inexcessof 450kglm
l
should not be usedunlessspecialconsiderationhas
IS456:2000
been given in design to the increased riskofcracking
due to
dryingshrinkage in.thin sections, or to early
thermalcracking andto theincreasedrisk of
damage
duetoalkalisilicareactions.
Table 4RequirementsforConcreteExposed toSulphateAttack
(Clauses8.2.2.4and9.1.2)
Percent gil gil
(I)(2) (3.) (4) (5)
1) Traces LessthanLessthan
«0.2) 1.0 n.3
ConcentrationofSuJpbates,
ExpresseduSOJ
....
SI
No.
ClaVi
... 1..-~oil,
TotalSOl SOlin
2:1Water:
SoilExtract
InGround
Water
Typeof Cement
(6)
Ordinary Portland
cement or Portland
slag cement or
Portlandpozzolana
cement
Dense,ruDyCompactedConcrete.
Made wltb 20 mmNominal
Maximum SizeAllre.ate.
ComplyIDlwitbIS383
# ,
Minimum Maximum
Cement FaceWater-
Content Cement
kllm
J
Ratio
(7) (8)
280 0.5S
iv)4 10to 11[0 2.5to
2.0 S,O 50
v) 5 Morethin MorechanMorethan
2.0 5.0 5.0
ii)
iii)
2 0.2 to
0.5
0.5
to
1.0
1.0to
1.9
1.91U
3.1
0.3to
1.2
1.110
2.5
Ordinary Portland
cement or
Portlandslag
cementor
Portland
pozzolanacement
Supersulphated
cement or
sulphateresisting
Portlandcement
Supersulphated
cement or
sulphateresisting
Portland cement
Portlandpozzolana
cement or Portland
slag cement
Supersulphatcd
or sulphate
resisting
Portland
cement
Sulphateresisting,.
Portlandcementor
supersulphatedc;eanent
withprotectivecoatings
330
310
330
350
370
4(X)
0.50
o.so
0.50
0.45
O,4S
0.40
NOTES
1 Cement content given in this tableisIrrespectiveofgradesofcement.
2Use of supersulphatedcement isgenerallyrestrictedwheretheprevailingtemperatureisabove40f'C.
3Supersutpbated cementgivesanacceptable life providedthatthe concrete is dense andpreparedwithawater-cementratio of 0.4 or
less, inmineralacids,down topH3.~.
4 Thecementcontents given incol6 ofthistablearetheminimum recommended. ForSO,contentsneartheupperlimit ofanyclass.
cement contents above theseminimumareadvised.
5 For severeconditions.such ~thinsectionsunderhydrostaticpressureononeside onlyandsectionspantyimmersed.considerations
should
begiven to
afurther reduction ofwater-cementratio.
6PortlandslagcementconformingtoIS45.5withslagcontentmorethan50percentexhibitsbettersulphateresisting properties.
7 Where chl()ride is encountered alongwith sulphates in soilorgroundwater.ordinaryPortlandcement with C1Acontentfrom~to8
percent shall
bedesirable to
heused in concrete,insteadof sulphateresistingcement.Alternatively.Portland ~lllgermentconforming
to IS4~~havingmorethan~opercentslagOfa blendofordinaryPortlandcementandslagmaybeused providedsutlicient information
is available on
performanceof.
suchblended cements intheseconditions.
19
IS456:2000
8.2.5Mix Constituents
8.2.5.1General
For concrete to be durable,carefulselectionof the mix
andmaterialsisnecessary, sothatdeleterious
constituents do not exceed the limits.
8.2.5.1Chloridesinconcrete
Whenever there is chloride in concrete there is an
increased
riskofcorrosionofembeddedmetal.
The
higherthechloridecontent, orifsubsequentlyexposed
to warm moistconditions.the greater the risk of
corrosion. All constituents
maycontain chlorides and
. concrete
may
becontaminatedbychlorides from the
external environment. To minimize the chances of
deterioration
ofconcretefromharmfulchemicalsalts,
the levels of such harmful salts in concrete coming
from concrete materials, that is, cement, aggregates
waterand admixtures.as well as
bydiffusionfromthe
environment should
belimited.Thetotal amount of
chloridecontent (as Cl) in the concrete at the time of
placingshall be as giveninTable 7.
The
totalacid soluble chloride content should be
calculated
fromthe mix proportionsand the measured
chloridecontentsof each of theconstituents.Wherever
possible, the total chloride content of the concrete
should
bedetermined,
8.2.5.3 Sulphates inconcrete
Sulphates are present in most cements and in some
aggregates;excessiveamountsofwater-soluble
sulphatefromtheseor other mixconstituentscancause
expansionand
disruptionofconcrete.Topreventthis,
the totalwater-solublesulphatecontentof the
concrete
mix.expressed
asSOl'shouldnotexceed4percentby
massofthecement inthemix. The sulphatecontent
should be calculated as the totalfromthevarious
constituents of the mix.
The 4 percentlimitdoes not
applytoconcretemade
withsupersulphatedcementcomplyingwithIS6909.
8.2.5.4Alkali-aggregatereaction
Some aggregates containing particular varieties of
silica
maybe susceptible to attackbyalkalis
(N~O
and~O)originatingfromcement or other sources,
producing an expansive reaction which can cause
cracking and disruption of concrete. Damage to
concrete from this reaction willnormallyonly occur
when all the following are present together:
a) A high moisture level, within the concrete;
b) A cement
withhigh alkali content, or another
source of
alkali;
c)Aggregatecontaininganalkalireactive
constituent.
Where theservicerecords ofparticular
cementl
aggregatecombinationare wellestablished,anddo not
include anyinstancesofcrackingdue to alkali
aggregate reaction, no further precautions should
be
necessary.Whenthematerialsareunfamiliar,
precautionsshould take one or more of the following
forms:
a) Use of non-reactive aggregate from alternate
sources.
Table5 MinimumCementContent,MaximumWater-CementRatio andMinimumGradeofConcrete
for
DifTerentExposureswithNormalWeightAggregates of20mmNominalMaximumSize
(Clause»6.1.2,8.2.4.1and9.1.2)
SI
No.
i)
iii)
iii)
iv)
v)
t;xposure PlainConcrete ReinforcedConcrete
~
....
" --
... ...
Minimum Maximum Minimum Minimum Maxirnum Minimum
Cement FreeWater· Gradeof Cement FreeWater- Gradeof
Content CementRatio Concrete Content CementRatio Concrete
kglm' kgln}l
(2) (3) (4) (~) (6) (7) (8)
Mild 220 0.60 300 O.5~ M20
Moderate 240 0.60 MIS 300 O.SO M25
Severe 2S0 O.SO M20 320 O.4~ MJO
Verysevere 260 0.45 M20 340 0.45 M3S
Extreme ~80 0.40 M2~ 360 0.40 M40
NC)T&,
ICelnentcontentprescribedinthistableisirrapeetiveofthegrDdesofcementandit isinclusiveofadditionsmentionedin5.2.The
additionssuchDIflyashoraroundgranulatedblastfurnaceslagmayhetakenintoICcountintheconcretecompositionwithrespecllO
thecementcontentandwater-cementratioifthesuitabilityisestablishedandaslonlasthemaximum81nountscakcnintoac&.~untdo
notexceedthelimilorpozzolonaandalaespecifiedinIS1489(PartI)andIS4S~respectively.
2Minimumgrade·forplain concreteundermildexposu~conditionitnolspecified.
20
8.2.5Mix Constituents
8.2.5.1General
For concrete to be durable,carefulselectionof the mix
andmaterialsisnecessary, sothatdeleterious
constituents do not exceed the limits.
8.2.5.1Chloridesinconcrete
Whenever there is chloride in concrete there is an
increased
riskofcorrosionofembeddedmetal.
The
higherthechloridecontent, orifsubsequentlyexposed
to warm moistconditions.the greater the risk of
corrosion. All constituents
maycontain chlorides and
. concrete
may
becontaminatedbychlorides from the
external environment. To minimize the chances of
deterioration
ofconcretefromharmfulchemicalsalts,
the levels of such harmful salts in concrete coming
from concrete materials, that is, cement, aggregates
waterand admixtures.as well as
bydiffusionfromthe
environment should
belimited.Thetotal amount of
chloridecontent (as Cl) in the concrete at the time of
placingshall be as giveninTable 7.
The
totalacid soluble chloride content should be
calculated
fromthe mix proportionsand the measured
chloridecontentsof each of theconstituents.Wherever
possible, the total chloride content of the concrete
should
bedetermined,
8.2.5.3 Sulphates inconcrete
Sulphates are present in most cements and in some
aggregates;excessiveamountsofwater-soluble
sulphatefromtheseor other mixconstituentscancause
expansionand
disruptionofconcrete.Topreventthis,
the totalwater-solublesulphatecontentof the
concrete
mix.expressed
asSOl'shouldnotexceed4percentby
massofthecement inthemix. The sulphatecontent
should be calculated as the totalfromthevarious
constituents of the mix.
The 4 percentlimitdoes not
applytoconcretemade
withsupersulphatedcementcomplyingwithIS6909.
8.2.5.4Alkali-aggregatereaction
Some aggregates containing particular varieties of
silica
maybe susceptible to attackbyalkalis
(N~O
and~O)originatingfromcement or other sources,
producing an expansive reaction which can cause
cracking and disruption of concrete. Damage to
concrete from this reaction willnormallyonly occur
when all the following are present together:
a) A high moisture level, within the concrete;
b) A cement
withhigh alkali content, or another
source of
alkali;
c)Aggregatecontaininganalkalireactive
constituent.
Where theservicerecords ofparticular
cementl
aggregatecombinationare wellestablished,anddo not
include anyinstancesofcrackingdue to alkali
aggregate reaction, no further precautions should
be
necessary.Whenthematerialsareunfamiliar,
precautionsshould take one or more of the following
forms:
a) Use of non-reactive aggregate from alternate
sources.
Table5 MinimumCementContent,MaximumWater-CementRatio andMinimumGradeofConcrete
for
DifTerentExposureswithNormalWeightAggregates of20mmNominalMaximumSize
(Clause»6.1.2,8.2.4.1and9.1.2)
SI
No.
i)
iii)
iii)
iv)
v)
t;xposure PlainConcrete ReinforcedConcrete
~
....
" --
... ...
Minimum Maximum Minimum Minimum Maxirnum Minimum
Cement FreeWater· Gradeof Cement FreeWater- Gradeof
Content CementRatio Concrete Content CementRatio Concrete
kglm' kgln}l
(2) (3) (4) (~) (6) (7) (8)
Mild 220 0.60 300 O.5~ M20
Moderate 240 0.60 MIS 300 O.SO M25
Severe 2S0 O.SO M20 320 O.4~ MJO
Verysevere 260 0.45 M20 340 0.45 M3S
Extreme ~80 0.40 M2~ 360 0.40 M40
NC)T&,
ICelnentcontentprescribedinthistableisirrapeetiveofthegrDdesofcementandit isinclusiveofadditionsmentionedin5.2.The
additionssuchDIflyashoraroundgranulatedblastfurnaceslagmayhetakenintoICcountintheconcretecompositionwithrespecllO
thecementcontentandwater-cementratioifthesuitabilityisestablishedandaslonlasthemaximum81nountscakcnintoac&.~untdo
notexceedthelimilorpozzolonaandalaespecifiedinIS1489(PartI)andIS4S~respectively.
2Minimumgrade·forplain concreteundermildexposu~conditionitnolspecified.
20
1S4S6:2000
Table 7LimitsofChlorideContent orConcrete
(Clause8.2.5.2)
Thedestructiveactionofaggressivewaterson concrete
is progressiveeThe rateofdeteriorationdecreasesas
the concrete is madestrongerand
more impermeable,
and increasesas thesaltcontentofthewaterincreases.
Wherestructuresareonlypartiallyimmersedor are in
contactwithaggressivesoilsor
watersononesideonly,
SI
TypeorUse01Concrete MaximumTotal
No. Acid Soluble
ChlorideConteDt
Exp~cd asklhnJor
CODcrete
(I) (2) (3)
i) Concretecontainingmetaland 0.4
steamcuredatelevatedtempe-
ratureandpre-stressedconcrete
ii)Reinforcedconcreteor plainconcrete 0.6
containingembedded metal
iii) Concretenotcontainingembedded J.O
metaloranymaterialrequiring
protectionfrom chloride
b) Usc of low alkali ordinary Portland cement
having total alkalicontent not morethan 0.6
percent(as Na
20
equivalent).
Furtheradvantagecan be obtainedby useof fly
ash(GradeI)conformingto IS 3812 or
granulated blastfurnace slag conforming to
IS 12089aspartreplacement ofordinary
Portland cement (having total alkali
contentas
Na
2
0 equivalent notmore than 0.6percent),
providedfly·ashcontentis at least 20 percent
or slag content is at least 50
percent.
c) Measurestoreduce the degree ofsaturationof
theconcrete duringservicesuch as use of
impermeablemembranes,
d)Limitingthecementcontentin theconcretemix
and thereby limiting totalalkalicontent in the
concrete mix.Formore guidance specialist
literaturesmaybereferred.
8.2.6ConcreteinAggressiveSoils andWater
8.2.6.1General
8.1.6.2Drainage
At siteswherealkaliconcentrationsare high ormay
becomeveryhigh.thegroundwatershouldbelowered
bydrainage so thatitwillnotcome intodirectcontact
withtheconcrete.
Additional protectionmaybeobtainedbythe use of
chemicallyresistantstone facing or a layer of plaster
of Paris coveredwithsuitablefabric,such as jute
thoroughly impregnatedwith bituminousmaterial.
8.2.7Compaction;Finishingand Curing
Adequatecompactionwithoutsegregationshouldbe
ensuredby providing suitable workabilityandby
employingappropriateplacingandcompacting
equipmentandprocedures.Full
compactionis
particularly
importantinthevicinityofconstruction
and
movementjoints andofembeddedwaterbars and
reinforcement.
Good finishingpracticesare essentialfor durable
concrete.
Overworkingthesurfaceand the additionof waterl
cement to aid infinishingshouldbe avoided; the
resulting laitance
will haveimpairedstrengthand
durabilityand will be particularlyvulnerableto
freezing
and thawingunderwetconditions.
Itisessentialtouseproper and adequatecuring
techniques to reduce thepermeabilityoftheconcrete
andenhanceits durability byextendingthe hydration
of the
cement,particularlyinitssurfacezone
isee
13.5).
8.2.8 Concrete inSea-water
Concrete
i~sea-wateror exposeddirectlyalongthe
sea-coastshallbeat least M 20 Gradeinthe case of
plainconcreteandM 30incaseofreinforcedconcrete.
Theuse of slagorpozzolanacementisadvantageous
under such conditions.
8.2.8.1SPecialattentionshallbegiven tothedesign
ofthemixto obtainthedensestpossibleconcrete;slag.
broken brick. soft limestone, softsandstone,orother
porousor weak aggregatesshall notbe used.
8.2.8.2As faraspossible,preferenceshallbegivento
precast
membersunreinforced,well-curedand
hardened.withoutsharp corners, and havingtrowel
smoothfinishedsurfacesfree fromcrazing.cracks or
other defects;plasteringshould
beavoided.
8.2.8.3Noconstructionjointsshallbeallowedwithin
600 mm below lowwater-levelor within 600 mm of
the upper and
lowerplanes of waveaction.
Where
evaporationmaycause seriousconcentrationsof salts
withsubsequentdeterioration,even where theoriginal
.salt contentof the soil or water
isnothigh.
NOTE-
Guidancefeaardingrequirementsforconaeteexposed
10sulphnteanaek islivenin1~4.
AdjustmentstoMinimumCemeDt
ContentsIn1able5
k&lm:-
(3)
+40
o
-30
(2)
10
20
40
Nominal
Maximum
AarepteSize
mm
Table6Adjustmentsto Minimum Cement
ContentsforAllregatesOtherThan20mm
Nominal Maximum Size
(Clause8.2.4.1)
(I)
i)
ii)
iii)
SI
No.
21
Table 7LimitsofChlorideContent orConcrete
(Clause8.2.5.2)
Thedestructiveactionofaggressivewaterson concrete
is progressiveeThe rateofdeteriorationdecreasesas
the concrete is madestrongerand
more impermeable,
and increasesas thesaltcontentofthewaterincreases.
Wherestructuresareonlypartiallyimmersedor are in
contactwithaggressivesoilsor
watersononesideonly,
SI
TypeorUse01Concrete MaximumTotal
No. Acid Soluble
ChlorideConteDt
Exp~cd asklhnJor
CODcrete
(I) (2) (3)
i) Concretecontainingmetaland 0.4
steamcuredatelevatedtempe-
ratureandpre-stressedconcrete
ii)Reinforcedconcreteor plainconcrete 0.6
containingembedded metal
iii) Concretenotcontainingembedded J.O
metaloranymaterialrequiring
protectionfrom chloride
b) Usc of low alkali ordinary Portland cement
having total alkalicontent not morethan 0.6
percent(as Na
20
equivalent).
Furtheradvantagecan be obtainedby useof fly
ash(GradeI)conformingto IS 3812 or
granulated blastfurnace slag conforming to
IS 12089aspartreplacement ofordinary
Portland cement (having total alkali
contentas
Na
2
0 equivalent notmore than 0.6percent),
providedfly·ashcontentis at least 20 percent
or slag content is at least 50
percent.
c) Measurestoreduce the degree ofsaturationof
theconcrete duringservicesuch as use of
impermeablemembranes,
d)Limitingthecementcontentin theconcretemix
and thereby limiting totalalkalicontent in the
concrete mix.Formore guidance specialist
literaturesmaybereferred.
8.2.6ConcreteinAggressiveSoils andWater
8.2.6.1General
8.1.6.2Drainage
At siteswherealkaliconcentrationsare high ormay
becomeveryhigh.thegroundwatershouldbelowered
bydrainage so thatitwillnotcome intodirectcontact
withtheconcrete.
Additional protectionmaybeobtainedbythe use of
chemicallyresistantstone facing or a layer of plaster
of Paris coveredwithsuitablefabric,such as jute
thoroughly impregnatedwith bituminousmaterial.
8.2.7Compaction;Finishingand Curing
Adequatecompactionwithoutsegregationshouldbe
ensuredby providing suitable workabilityandby
employingappropriateplacingandcompacting
equipmentandprocedures.Full
compactionis
particularly
importantinthevicinityofconstruction
and
movementjoints andofembeddedwaterbars and
reinforcement.
Good finishingpracticesare essentialfor durable
concrete.
Overworkingthesurfaceand the additionof waterl
cement to aid infinishingshouldbe avoided; the
resulting laitance
will haveimpairedstrengthand
durabilityand will be particularlyvulnerableto
freezing
and thawingunderwetconditions.
Itisessentialtouseproper and adequatecuring
techniques to reduce thepermeabilityoftheconcrete
andenhanceits durability byextendingthe hydration
of the
cement,particularlyinitssurfacezone
isee
13.5).
8.2.8 Concrete inSea-water
Concrete
i~sea-wateror exposeddirectlyalongthe
sea-coastshallbeat least M 20 Gradeinthe case of
plainconcreteandM 30incaseofreinforcedconcrete.
Theuse of slagorpozzolanacementisadvantageous
under such conditions.
8.2.8.1SPecialattentionshallbegiven tothedesign
ofthemixto obtainthedensestpossibleconcrete;slag.
broken brick. soft limestone, softsandstone,orother
porousor weak aggregatesshall notbe used.
8.2.8.2As faraspossible,preferenceshallbegivento
precast
membersunreinforced,well-curedand
hardened.withoutsharp corners, and havingtrowel
smoothfinishedsurfacesfree fromcrazing.cracks or
other defects;plasteringshould
beavoided.
8.2.8.3Noconstructionjointsshallbeallowedwithin
600 mm below lowwater-levelor within 600 mm of
the upper and
lowerplanes of waveaction.
Where
evaporationmaycause seriousconcentrationsof salts
withsubsequentdeterioration,even where theoriginal
.salt contentof the soil or water
isnothigh.
NOTE-
Guidancefeaardingrequirementsforconaeteexposed
10sulphnteanaek islivenin1~4.
AdjustmentstoMinimumCemeDt
ContentsIn1able5
k&lm:-
(3)
+40
o
-30
(2)
10
20
40
Nominal
Maximum
AarepteSize
mm
Table6Adjustmentsto Minimum Cement
ContentsforAllregatesOtherThan20mm
Nominal Maximum Size
(Clause8.2.4.1)
(I)
i)
ii)
iii)
SI
No.
21
IS456:1000
unusuallysevereconditionsor abrasionareanticipated,
suchpartsof the workshall
beprotectedbybituminous
orsilico-fluoridecoatingsor stonefacingbeddedwith
bitumen.
8.2.8.4 In reinforcedconcretestructures,care shall
he
takento protect the reinforcement from exposure to
saline atmosphereduring storage,fabricationand use.
It
maybeachievedbytreatingthesurfaceof
reinforcementwithcementwash or bysuitable
methods.
9CONCRETEMIXPROPORTIONING
9.1MixProportion
The mix proportions shallbeselected to ensure the
workabilityof the freshconcrete and
whenconcrete
is
hardened,it shallhavetherequiredstrength,durability
and surface
finish.
9.1.1 The determinationof the proportionsof cement,
aggregates and water to attain the required strengths
shall he made as follows:
a)
Bydesigning the concrete mix; such concrete
shall
becalled 'Design mix concrete', or
b) Byadoptingnominal concretemix:such
concreteshallbecalled 'Nominalmixconcrete'.
Design mix concrete is preferred to nominal mix. If
design mix concretecannot
beused for any reason on
thework for grades of M 20 orlower)nominal mixes
maybeusedwiththepermissionofengineer-in-charge.
which, however. islikelyto involve a higher cement
content.
9.1.2InformationRequired
Inspecifyingaparticular gradeofconcrete,the
following informationshall
beincluded:
a)
Typeof mix, that is, design mix concreteOf
nominal mix concrete:
h)Gradedesignation;
c) Type of cement;
d) Maximum nominal size of aggregate;
e)Minimumcement cont.ent(for design mix
concrete);
f)Maximumwater-cementratio;
g)Workability;
h) Mix proportion (for nominalmix concrete);
j)Exposureconditions as per Tables 4 and5;
k) Maximum temperature of concrete at the time
of placing;
m) Method of
placing;and
n) Degree of supervision.
9.1.2.1In appropriatecircumstances.the following
additional information
maybespecified:
a)
Typeof aggregate,
b)Maximum cement
content.and
c)Whetheran admixtureshall orshallnot be
used and thetype ofadmixtureand the
condition of use.
9.2DesignMixConcrete
9.2.1Astheguarantorof quality ofconcreteused in
theconstruction,theconstructorshallcarryoutthemix
design and the mix sodesigned(notthe methodof
design) shall
beapprovedbythe employer within
the
limitations of parameters and other stipulations laid
down
bythis standard.
9.2.2The mix shallbedesigned to produce thegrade
of concrete having the required workability and a
characteristicstrengthnotlessthanappropriatevalues
given in Table2. The targetmean strengthof concrete
mix shouldbe equal to the characteristicstrengthplus
1.65 times the standarddeviation.
9.2.3Mix design done earlier not prior to one year
maybe considered adequate for later work provided
there is.no change in source and the quality of the
materials,
9.2.4StandardDeviation
Thestandarddeviationforeachgradeofconcreteshall
becalculated,separately.
9.2.4.1Standarddeviation bluedon test
strengthof
sample
a)Numberoftest resultsofsample,s'-Thetotal
numberof test strength of samples required to
constitute an acceptable recordfarcalculation
of standarddeviation shallbenot less than 30.
Attemptsshould be madetoobtainthe 30
,samples,asearlyaspossible,whena mixis used
for the first time.
b)In caseof
significantchangesin concrete
Whensignificantchanges are made in the
production of concrete batches (for example
changes in thematerials used, mix design,
equipment or technical
control).the standard
deviation value
shanbe separately calculated
for such batches of concrete.
c)Standard
deviationtobebrough: up todate
The calculationof the standard deviation shall
bebroughtup to date afterevery change of mix
design.
9.2.4.2Assumedstandarddeviation
Where sufficient test results for a particular grade of
concrete are not available. the value of standard
deviation given inTable8maybeassumed for design
of mix in the first instance. As soon as the results of
samples are available, actual calculated standard
deviationshall
beusedand themix designedproperly.
22
unusuallysevereconditionsor abrasionareanticipated,
suchpartsof the workshall
beprotectedbybituminous
orsilico-fluoridecoatingsor stonefacingbeddedwith
bitumen.
8.2.8.4 In reinforcedconcretestructures,care shall
he
takento protect the reinforcement from exposure to
saline atmosphereduring storage,fabricationand use.
It
maybeachievedbytreatingthesurfaceof
reinforcementwithcementwash or bysuitable
methods.
9CONCRETEMIXPROPORTIONING
9.1MixProportion
The mix proportions shallbeselected to ensure the
workabilityof the freshconcrete and
whenconcrete
is
hardened,it shallhavetherequiredstrength,durability
and surface
finish.
9.1.1 The determinationof the proportionsof cement,
aggregates and water to attain the required strengths
shall he made as follows:
a)
Bydesigning the concrete mix; such concrete
shall
becalled 'Design mix concrete', or
b) Byadoptingnominal concretemix:such
concreteshallbecalled 'Nominalmixconcrete'.
Design mix concrete is preferred to nominal mix. If
design mix concretecannot
beused for any reason on
thework for grades of M 20 orlower)nominal mixes
maybeusedwiththepermissionofengineer-in-charge.
which, however. islikelyto involve a higher cement
content.
9.1.2InformationRequired
Inspecifyingaparticular gradeofconcrete,the
following informationshall
beincluded:
a)
Typeof mix, that is, design mix concreteOf
nominal mix concrete:
h)Gradedesignation;
c) Type of cement;
d) Maximum nominal size of aggregate;
e)Minimumcement cont.ent(for design mix
concrete);
f)Maximumwater-cementratio;
g)Workability;
h) Mix proportion (for nominalmix concrete);
j)Exposureconditions as per Tables 4 and5;
k) Maximum temperature of concrete at the time
of placing;
m) Method of
placing;and
n) Degree of supervision.
9.1.2.1In appropriatecircumstances.the following
additional information
maybespecified:
a)
Typeof aggregate,
b)Maximum cement
content.and
c)Whetheran admixtureshall orshallnot be
used and thetype ofadmixtureand the
condition of use.
9.2DesignMixConcrete
9.2.1Astheguarantorof quality ofconcreteused in
theconstruction,theconstructorshallcarryoutthemix
design and the mix sodesigned(notthe methodof
design) shall
beapprovedbythe employer within
the
limitations of parameters and other stipulations laid
down
bythis standard.
9.2.2The mix shallbedesigned to produce thegrade
of concrete having the required workability and a
characteristicstrengthnotlessthanappropriatevalues
given in Table2. The targetmean strengthof concrete
mix shouldbe equal to the characteristicstrengthplus
1.65 times the standarddeviation.
9.2.3Mix design done earlier not prior to one year
maybe considered adequate for later work provided
there is.no change in source and the quality of the
materials,
9.2.4StandardDeviation
Thestandarddeviationforeachgradeofconcreteshall
becalculated,separately.
9.2.4.1Standarddeviation bluedon test
strengthof
sample
a)Numberoftest resultsofsample,s'-Thetotal
numberof test strength of samples required to
constitute an acceptable recordfarcalculation
of standarddeviation shallbenot less than 30.
Attemptsshould be madetoobtainthe 30
,samples,asearlyaspossible,whena mixis used
for the first time.
b)In caseof
significantchangesin concrete
Whensignificantchanges are made in the
production of concrete batches (for example
changes in thematerials used, mix design,
equipment or technical
control).the standard
deviation value
shanbe separately calculated
for such batches of concrete.
c)Standard
deviationtobebrough: up todate
The calculationof the standard deviation shall
bebroughtup to date afterevery change of mix
design.
9.2.4.2Assumedstandarddeviation
Where sufficient test results for a particular grade of
concrete are not available. the value of standard
deviation given inTable8maybeassumed for design
of mix in the first instance. As soon as the results of
samples are available, actual calculated standard
deviationshall
beusedand themix designedproperly.
22
Table 8 AssumedStandardJleviation
(Clau~'e9.2.4.2andTub/£'11)
However,whenadequatepastrecordsforasimilargrade
existandjustifytothedesigneravalueofst,Uldarddeviation
differentfromthatshowninTable8,itshallbepermissible
tousethatvalue.
9.3NominalMixConcrete
Nominalmixconcretemaybeusedforconcreteof
M 20 or lower. Theproportionsofruutcnalsfor
nominal mix concrete shall be inaccordancewith
1:1ble9.
9.3.1 The cement'contentofthe mixspecifiedin
Table9foranynominal mix shallbeproportionately
increasedifthequantityofwater in a nuxhastohe
increasedto overcor..e thedifficultiesof placementand
compaction, so thatthewater-cementratioasspecified
isnotexceeded.
IS456:2000
10PRODUCTIONOF CONCRETE
10.1QualityAssuranceMeasures
10.1.1 Inorderthat thepropertiesof the completed
structure
beconsistentwiththe requirements and the
assumptions made during the planning and the design,
adequatequality assurance measures shallbetaken.
The construction should result in satisfactory strength,
serviceability and long term durability so as to lower
theoveralllife-cyclecost.Quality assurancein
construction
activityrelates to proper design, usc of
adequate materials and components to
besupplied by
the producers, proper workmanship in the execution
of works by the contractor and ultimately proper care
duringthe useofstructureincludingtimely
maintenance and repairbythe owner.
10.J.2Quality assurance measures arebothtechnical
and organizational. Some common cases should
be
specified in a general Quality Assurance Plan which
shall
identifythekeyelementsnecessary to provide
fitness of the structure and the means
bywhichthey
are to beprovidedandmeasuredwiththeoverall
purpose to provide confidence that the realized project
will worksatisfactorilyin
servicefulfillingintended
needs. Thejob ofqualitycontrol andqualityassurance
wouldinvolve quality auditofboththeinputsas well
as
theoutputs.Inputsare in the form of materials for
concrete:
workmanshipin allstagesofhatching.
mixing,transportation,placing,compactionand
curing:and therelatedplant,machineryand
equipments:resultingin theoutputin the form of
concrete in place. To ensure
properperformance,itis
necessary thateachstepinconcretingwhichwi11be
covered
bythenext stepisinspectedasthework
proceeds(seealso17).
4.0
l5
5.0
AS5Uftl,dStKndard
Deviation
N/narn
z
Gradeof
Concrete
MIO
MIS
M20
M2S
MJO
MJS
M40
M4S
MSO
NOTE--The above valuescorrespondto thesitecontrolhaving
properstorageofcement;weighhatchingofallmaterial»;controlled
addition ofwater;regularcheckingofall,nate.-juls.ag~rcgate
&J'adingsand moisturecontent;andperiodicalchecking of
work3hilityandstrength.W~rctherei~deviationfromth~above
the valuesgivenintheabnvetnbleshallheinc.:fea~cd hyIN/nun!.
Table«)ProportionsforNominalMixConcrete
(Clausrs9.3lind9.~.l)
Gradeof
Concrete
TotalQuantityofDryAggre
gatesbyi\lassper SOkgof
Cement,tobeTakenastheSUID
oftheIndividualM1I$..'iesof
FtntaodCoarseAl:gregH1es,kg,
MtlX
PreportionofFine
A~gregate to~oarse
Axgre"ate(hyl\1a'tt)
QuantityofWat~rper
SOkgofCement,Max
I
(I)
M5
M7.~
M 10
M15
M20
(2)
ROO
625
480
330
2~O
Generally 1:2butsubjectto
an upperlimit of I: 1
1'1anda
lowerlimit of1:2
1
/1.
(4)
60
45
34
32
30
NOTE-11leproportionofthefinetocoarseaggregatesshouldbeadjustedfromupperlimit10lowerlimitprogressivelyasthe~rading
of fineagl~gates becomes finer andthemaximumsizeofcoarsea~gregate becomes larger,Graded coarseaggregateshallbeused.
Examplt
ForMAvera,,,,radinaoffineaggregate(that is. Zone IIofTable4ofIS~83).the proportionsshallbeL 1'1"1:1andl:2'/:!for
maximumsizeofngg~gntes 10mm,20mmand40mmrespectively,
23
(Clau~'e9.2.4.2andTub/£'11)
However,whenadequatepastrecordsforasimilargrade
existandjustifytothedesigneravalueofst,Uldarddeviation
differentfromthatshowninTable8,itshallbepermissible
tousethatvalue.
9.3NominalMixConcrete
Nominalmixconcretemaybeusedforconcreteof
M 20 or lower. Theproportionsofruutcnalsfor
nominal mix concrete shall be inaccordancewith
1:1ble9.
9.3.1 The cement'contentofthe mixspecifiedin
Table9foranynominal mix shallbeproportionately
increasedifthequantityofwater in a nuxhastohe
increasedto overcor..e thedifficultiesof placementand
compaction, so thatthewater-cementratioasspecified
isnotexceeded.
IS456:2000
10PRODUCTIONOF CONCRETE
10.1QualityAssuranceMeasures
10.1.1 Inorderthat thepropertiesof the completed
structure
beconsistentwiththe requirements and the
assumptions made during the planning and the design,
adequatequality assurance measures shallbetaken.
The construction should result in satisfactory strength,
serviceability and long term durability so as to lower
theoveralllife-cyclecost.Quality assurancein
construction
activityrelates to proper design, usc of
adequate materials and components to
besupplied by
the producers, proper workmanship in the execution
of works by the contractor and ultimately proper care
duringthe useofstructureincludingtimely
maintenance and repairbythe owner.
10.J.2Quality assurance measures arebothtechnical
and organizational. Some common cases should
be
specified in a general Quality Assurance Plan which
shall
identifythekeyelementsnecessary to provide
fitness of the structure and the means
bywhichthey
are to beprovidedandmeasuredwiththeoverall
purpose to provide confidence that the realized project
will worksatisfactorilyin
servicefulfillingintended
needs. Thejob ofqualitycontrol andqualityassurance
wouldinvolve quality auditofboththeinputsas well
as
theoutputs.Inputsare in the form of materials for
concrete:
workmanshipin allstagesofhatching.
mixing,transportation,placing,compactionand
curing:and therelatedplant,machineryand
equipments:resultingin theoutputin the form of
concrete in place. To ensure
properperformance,itis
necessary thateachstepinconcretingwhichwi11be
covered
bythenext stepisinspectedasthework
proceeds(seealso17).
4.0
l5
5.0
AS5Uftl,dStKndard
Deviation
N/narn
z
Gradeof
Concrete
MIO
MIS
M20
M2S
MJO
MJS
M40
M4S
MSO
NOTE--The above valuescorrespondto thesitecontrolhaving
properstorageofcement;weighhatchingofallmaterial»;controlled
addition ofwater;regularcheckingofall,nate.-juls.ag~rcgate
&J'adingsand moisturecontent;andperiodicalchecking of
work3hilityandstrength.W~rctherei~deviationfromth~above
the valuesgivenintheabnvetnbleshallheinc.:fea~cd hyIN/nun!.
Table«)ProportionsforNominalMixConcrete
(Clausrs9.3lind9.~.l)
Gradeof
Concrete
TotalQuantityofDryAggre
gatesbyi\lassper SOkgof
Cement,tobeTakenastheSUID
oftheIndividualM1I$..'iesof
FtntaodCoarseAl:gregH1es,kg,
MtlX
PreportionofFine
A~gregate to~oarse
Axgre"ate(hyl\1a'tt)
QuantityofWat~rper
SOkgofCement,Max
I
(I)
M5
M7.~
M 10
M15
M20
(2)
ROO
625
480
330
2~O
Generally 1:2butsubjectto
an upperlimit of I: 1
1'1anda
lowerlimit of1:2
1
/1.
(4)
60
45
34
32
30
NOTE-11leproportionofthefinetocoarseaggregatesshouldbeadjustedfromupperlimit10lowerlimitprogressivelyasthe~rading
of fineagl~gates becomes finer andthemaximumsizeofcoarsea~gregate becomes larger,Graded coarseaggregateshallbeused.
Examplt
ForMAvera,,,,radinaoffineaggregate(that is. Zone IIofTable4ofIS~83).the proportionsshallbeL 1'1"1:1andl:2'/:!for
maximumsizeofngg~gntes 10mm,20mmand40mmrespectively,
23
IS456:2000
ApproximateQuantityofSurface
Water..
Table 10SurfaceWaterCarriedbyAggregate
(Clause10.2.5)
10.2.6 No substitutionsin materials used on the work
or alterationsin theestablished proportions.except as
permitted in 10.2.4 and 10.2.Sshall
bemade without
additional tests to show that the quality and strength
of concrete aresatisfactory.
(4)
120
80
40
20-40
(3)
7.5
5.0
2.5
1.25-2,5
IICourserthe oggregllte.
less thewllterit willcorry.
(I) (2)
i)Verywetsand
ii)Modernlel)'wet sand
iii)Moistsand
IV)"Moistgravelorcrushedrock
10.3Mixing
Concrete shanbemixed in a mechanical mixer. The
mixer should comply with IS179"and IS12119.The
mixersshallbefitted withwatermeasuring(metering)
devices. The mixingshall be continueduntil there is a
uniform distribution of the materials and the mass is
mea.sured and within
±3 pereent of the quantity of
aggregate.admixturesand water being measured.
10.2.3ProportionflYpeandgradingofaggregatesshall
bemade by trial in such a way soasto obtain densest
possible concrete. All ingredients of the concrete
should be used by mass only.
10.2.4
Volumebatching may be allowed only where
weigh-batchingis not practical and provided accurate
bulk densities of materials to be
actuallyused in
concrete haveearlier beenestablished. Allowancefor
bulking shall be made in accordance with IS 2386
(Part 3). The mass volume relationship should be
checkeda.sfrequentlyasnecessary.the frequency for
the givenjob beingdetermined
byengineer-in-charge
10ensure that the specified grading is maintained,
10.2.S
Itis important to maintain thewater-cement
ratioconstant at itscorrectvalue.Tothisend. determi
nation of moisture contents in both fine and coarse
aggregatesshall
bemade as frequentlyas possible.the
frequency for a given job being determined by the
engineer-in-chargeaccording to weather conditions.
The amount of the added water shall be adjusted to
compensateforanyobservedvariationsin themoisture
contents. For thedeterminationof moisture content
in the
aggregates.IS 2386 (Part 3) maybereferred to.
To allow for the variation in mass of aggregatedue to
variationintheirmoisturecontent,suitableadjustments
in the massesof aggregatesshall also be made. In the
absence of exact data. only in the case of nominal
mixes.the amount of surface water may be estimated
from the valuesgiven in Table 10.
10.2Batching
Toavoidconfusionanderrorinbatching,consideration
should begivento usingthe smallest practicalnumber
ofdifferent concrete mixesonany site or inanyone
plant. Inhatchingconcrete.thequantityof bothcement
and aggregateshall
bedeterminedby
mass;admixture.
if solid. by mass; liquid admixture may however
be
measured in volume or mass; water shallbeweighed
OJ'measured
byvolume in a calibrated tank(set'also
IS 4925).
Ready-mixedconcretesuppliedbyready-mixed
concreteplantshall
bepreferred.Forlargeandmedium
project sites the concreteshall
besourced from ready
mixedconcreteplants or from on site or off site
hatching and mixing plants
(seeIS 4926).
10.2.1Except where itcan
heshowntothesatisfaction
of theengineer-in-chargethat supply of properly
gradedaggregateof uniformqualitycanbemaintained
over a period of work. the gradingof aggregateshould
be controlled
byobtaining the coarse aggregate in
different
sizesandblendingthemin the
right
proportions when required. thedifferentsizes being
stocked in separate stock-piles. The material should
bestock-piledfor severalhourspreferablyaday before
use. The grading ofcoarseand fine aggregate should
becheckedasfrequentlya.s possible. the frequency
for a given job being determinedbythe engineer-in
chargeto
ensurethat thespecifiedgradingis
maintained. 10.2.2The accuracyof the measuringequipmentshall
bewithin±2 percent of the quantity of cement being
10.1.3 Each party involved in the realization of a
project should establish and implement a Quality
Assurance Plan. for its participation in the project.
Supplier'sandsubcontractor'sactivitiesshall be
coveredin the plan. TheindividualQualityAssurance
Plans shall tit into the generalQualityAssurancePlan.
A Quality Assurance Plan shall define the tasks and
responsibilitiesof all persons involved. adequate
controland checking procedures,and the organization
andmaintainingadequatedocumentationof the
building process anditsresults. Such documentation
should generally include:
a) test reports and manufacturer's certificate for
materials. concrete mix design details;
b) pour cards for siteorganizationand clearance
for concrete placement;
c) record of site inspectionofworkmanship,field
tests;
d)non-conformancereports. change orders;
e) quality control charts; and
1)statistical analysis.
NOTE-Quahtycontrot chartsarerecommendedwhereverthe
concreteis in continuousproductionover considerableperiod.
. 24
ApproximateQuantityofSurface
Water..
Table 10SurfaceWaterCarriedbyAggregate
(Clause10.2.5)
10.2.6 No substitutionsin materials used on the work
or alterationsin theestablished proportions.except as
permitted in 10.2.4 and 10.2.Sshall
bemade without
additional tests to show that the quality and strength
of concrete aresatisfactory.
(4)
120
80
40
20-40
(3)
7.5
5.0
2.5
1.25-2,5
IICourserthe oggregllte.
less thewllterit willcorry.
(I) (2)
i)Verywetsand
ii)Modernlel)'wet sand
iii)Moistsand
IV)"Moistgravelorcrushedrock
10.3Mixing
Concrete shanbemixed in a mechanical mixer. The
mixer should comply with IS179"and IS12119.The
mixersshallbefitted withwatermeasuring(metering)
devices. The mixingshall be continueduntil there is a
uniform distribution of the materials and the mass is
mea.sured and within
±3 pereent of the quantity of
aggregate.admixturesand water being measured.
10.2.3ProportionflYpeandgradingofaggregatesshall
bemade by trial in such a way soasto obtain densest
possible concrete. All ingredients of the concrete
should be used by mass only.
10.2.4
Volumebatching may be allowed only where
weigh-batchingis not practical and provided accurate
bulk densities of materials to be
actuallyused in
concrete haveearlier beenestablished. Allowancefor
bulking shall be made in accordance with IS 2386
(Part 3). The mass volume relationship should be
checkeda.sfrequentlyasnecessary.the frequency for
the givenjob beingdetermined
byengineer-in-charge
10ensure that the specified grading is maintained,
10.2.S
Itis important to maintain thewater-cement
ratioconstant at itscorrectvalue.Tothisend. determi
nation of moisture contents in both fine and coarse
aggregatesshall
bemade as frequentlyas possible.the
frequency for a given job being determined by the
engineer-in-chargeaccording to weather conditions.
The amount of the added water shall be adjusted to
compensateforanyobservedvariationsin themoisture
contents. For thedeterminationof moisture content
in the
aggregates.IS 2386 (Part 3) maybereferred to.
To allow for the variation in mass of aggregatedue to
variationintheirmoisturecontent,suitableadjustments
in the massesof aggregatesshall also be made. In the
absence of exact data. only in the case of nominal
mixes.the amount of surface water may be estimated
from the valuesgiven in Table 10.
10.2Batching
Toavoidconfusionanderrorinbatching,consideration
should begivento usingthe smallest practicalnumber
ofdifferent concrete mixesonany site or inanyone
plant. Inhatchingconcrete.thequantityof bothcement
and aggregateshall
bedeterminedby
mass;admixture.
if solid. by mass; liquid admixture may however
be
measured in volume or mass; water shallbeweighed
OJ'measured
byvolume in a calibrated tank(set'also
IS 4925).
Ready-mixedconcretesuppliedbyready-mixed
concreteplantshall
bepreferred.Forlargeandmedium
project sites the concreteshall
besourced from ready
mixedconcreteplants or from on site or off site
hatching and mixing plants
(seeIS 4926).
10.2.1Except where itcan
heshowntothesatisfaction
of theengineer-in-chargethat supply of properly
gradedaggregateof uniformqualitycanbemaintained
over a period of work. the gradingof aggregateshould
be controlled
byobtaining the coarse aggregate in
different
sizesandblendingthemin the
right
proportions when required. thedifferentsizes being
stocked in separate stock-piles. The material should
bestock-piledfor severalhourspreferablyaday before
use. The grading ofcoarseand fine aggregate should
becheckedasfrequentlya.s possible. the frequency
for a given job being determinedbythe engineer-in
chargeto
ensurethat thespecifiedgradingis
maintained. 10.2.2The accuracyof the measuringequipmentshall
bewithin±2 percent of the quantity of cement being
10.1.3 Each party involved in the realization of a
project should establish and implement a Quality
Assurance Plan. for its participation in the project.
Supplier'sandsubcontractor'sactivitiesshall be
coveredin the plan. TheindividualQualityAssurance
Plans shall tit into the generalQualityAssurancePlan.
A Quality Assurance Plan shall define the tasks and
responsibilitiesof all persons involved. adequate
controland checking procedures,and the organization
andmaintainingadequatedocumentationof the
building process anditsresults. Such documentation
should generally include:
a) test reports and manufacturer's certificate for
materials. concrete mix design details;
b) pour cards for siteorganizationand clearance
for concrete placement;
c) record of site inspectionofworkmanship,field
tests;
d)non-conformancereports. change orders;
e) quality control charts; and
1)statistical analysis.
NOTE-Quahtycontrot chartsarerecommendedwhereverthe
concreteis in continuousproductionover considerableperiod.
. 24
18456:1000
These
tolerances
applytoconcretedimensionsonly,and
not
topositioniolof
verticalreinforcingsteelordowels.
11.2aeanm._TnatmeDt01Formwork
All rubbish,particularly,chippinss,shavings and
sawduatsballberemovedfromtheinteriorofthefonns
beforetheconcreteisplaced.Thefaceofformwork
incontactwiththeconcreteshallbecleanedandtreated
withformreleaseagent.Releaseagentsshouldbe
appliedsoasto providea thinunifonncoatingto the
fonns withoutcoatingthereinforcement.
11FORMWORK
11.1General
Theformworkshallbedesignedandconstructedso
as to remain sufficiently rigid during placing and
compactionofconcrete,andshallbesuchastoprevent
lossofslurryfrom theconcrete.For furtherdetails
regardingdesign,detailing,etc,referencemaybemade
to IS14687.Thetoleranceson theshapes,linesand
dimensionsshown
inthedrawingshallbewithinthe
limits
givenbelow:
ubifortnincolourandconsistenc.y.If there is
.e,re,ationalterunloadingfromthemixer,the
COhcreteshouldberemixed.
10.3.1Porguidance,the mixingtimeshallbeat least
2
min.Por othertypesofmore efficient mixers,
manufacturersrecommendationsshalJbefollowed;
forhydrophobiccement itmaybedecidedbythe
engineer-in-charge.
10.3.2Workabilityshouldbechecked atfrequent
intervals(IttIS1199).
10.3.3Dosagesofretarders,plasticisers and
superplasticisersshall berestrictedto O.S,1.0and2.0
percentrespectivelyby weightofcementitious
materialsandunlessahighervalue isagreedupon
betweenthe!Itllftufacturerandtheconstructorbased
onperformancetest.
11ASSEMBLYOFREINFORCEMENT
7days
14days
3 days
14 days
21days
7 days
MinimumPeriod
BeforeStriking
Formwork
16-24 h
TypeofFormwor/c
12.1Reinforcementshall be bent and fixed in
accordancewithprocedurespecifiedin IS 2502.The
highstrengthdefonnedsteelbarsshouldnotbere-bent
11.3Strlpplnl11me
Fonns shall not
bereleased until the concrete has
achievedastrengthofatleasttwice thestresstowhich
theconcretemay
besubjectedat the timeofremoval
offonnwork.Thestrengthreferredto shallbethatof
concreteusingthe same cement andaggregatesand
admixture,ifany,withthesameproportionsandcured
underconditionsoftemperatureandmoisturesimilar
to
thoseexistingon the work.
11.3.1Whiletheabovecriteriaofstrengthshall bethe
guidingfactorforremovalof formwork,innormal
circumstanceswhereambienttemperaturedoesnotfall
belowI
SOCandwhereordinaryPortlandcementisused
andadequatecuringisdone,followingstriWngperiod
maydeemtosatisfytheguideline
givenin11.3:
a) Verticalfonnworkto columns,
walls,beams
b)Soffitformworktoslabs
(Propsto
berefixed
immediatelyafterremoval
offormwork)
c) Soffitfonnwork to beams
(Propstobe refixed
immediatelyafterremoval
offormwork)
d)Propstoslabs:
1)Spanningupto4.5 m
2)
Spanningover4.Sm
e) Props tobeamsand arches:
1)Spanningup to 6 m
2)
Spanningover6 m
Forothercements andlowertemperature, the
strippingtimerecommendedabove maybesuitably
modified.
11.3.2The
'numberof propsleftunder,theirsizesand
dispositionshallbesuchas tobeable tosafelycarry
the full dead load of the slab, beamorarch asthecase
maybe tOlether withanyliveload likely to occur
duringcuringorfurtherconstruction.
11.3.3Wheretheshapeof theelementis suchthatthe
formworkhasre-entrantangles,theformworkshallbe
removedas soonaspossibleaftertheconcretehasset,
to avoidshrinkage cracking occurring duetothe
restraintimposed.
+12
_ 6mm
+50
mm
-12
0.02timesthe
width
ofthefoot
ing in thedirec
tionofdeviation
butnotmorethan
SOmm
±
o.ostimesthe
specified thick
ness
2)
Eccentricity
3)Thickness
a)Deviationfromspecified
dimensionsofcross-section
ofcolumns
aadbeams
b)Deviationfromdimensions
offootinss
1)
Dimensio.inplan
2118818/07-5
2S
These
tolerances
applytoconcretedimensionsonly,and
not
topositioniolof
verticalreinforcingsteelordowels.
11.2aeanm._TnatmeDt01Formwork
All rubbish,particularly,chippinss,shavings and
sawduatsballberemovedfromtheinteriorofthefonns
beforetheconcreteisplaced.Thefaceofformwork
incontactwiththeconcreteshallbecleanedandtreated
withformreleaseagent.Releaseagentsshouldbe
appliedsoasto providea thinunifonncoatingto the
fonns withoutcoatingthereinforcement.
11FORMWORK
11.1General
Theformworkshallbedesignedandconstructedso
as to remain sufficiently rigid during placing and
compactionofconcrete,andshallbesuchastoprevent
lossofslurryfrom theconcrete.For furtherdetails
regardingdesign,detailing,etc,referencemaybemade
to IS14687.Thetoleranceson theshapes,linesand
dimensionsshown
inthedrawingshallbewithinthe
limits
givenbelow:
ubifortnincolourandconsistenc.y.If there is
.e,re,ationalterunloadingfromthemixer,the
COhcreteshouldberemixed.
10.3.1Porguidance,the mixingtimeshallbeat least
2
min.Por othertypesofmore efficient mixers,
manufacturersrecommendationsshalJbefollowed;
forhydrophobiccement itmaybedecidedbythe
engineer-in-charge.
10.3.2Workabilityshouldbechecked atfrequent
intervals(IttIS1199).
10.3.3Dosagesofretarders,plasticisers and
superplasticisersshall berestrictedto O.S,1.0and2.0
percentrespectivelyby weightofcementitious
materialsandunlessahighervalue isagreedupon
betweenthe!Itllftufacturerandtheconstructorbased
onperformancetest.
11ASSEMBLYOFREINFORCEMENT
7days
14days
3 days
14 days
21days
7 days
MinimumPeriod
BeforeStriking
Formwork
16-24 h
TypeofFormwor/c
12.1Reinforcementshall be bent and fixed in
accordancewithprocedurespecifiedin IS 2502.The
highstrengthdefonnedsteelbarsshouldnotbere-bent
11.3Strlpplnl11me
Fonns shall not
bereleased until the concrete has
achievedastrengthofatleasttwice thestresstowhich
theconcretemay
besubjectedat the timeofremoval
offonnwork.Thestrengthreferredto shallbethatof
concreteusingthe same cement andaggregatesand
admixture,ifany,withthesameproportionsandcured
underconditionsoftemperatureandmoisturesimilar
to
thoseexistingon the work.
11.3.1Whiletheabovecriteriaofstrengthshall bethe
guidingfactorforremovalof formwork,innormal
circumstanceswhereambienttemperaturedoesnotfall
belowI
SOCandwhereordinaryPortlandcementisused
andadequatecuringisdone,followingstriWngperiod
maydeemtosatisfytheguideline
givenin11.3:
a) Verticalfonnworkto columns,
walls,beams
b)Soffitformworktoslabs
(Propsto
berefixed
immediatelyafterremoval
offormwork)
c) Soffitfonnwork to beams
(Propstobe refixed
immediatelyafterremoval
offormwork)
d)Propstoslabs:
1)Spanningupto4.5 m
2)
Spanningover4.Sm
e) Props tobeamsand arches:
1)Spanningup to 6 m
2)
Spanningover6 m
Forothercements andlowertemperature, the
strippingtimerecommendedabove maybesuitably
modified.
11.3.2The
'numberof propsleftunder,theirsizesand
dispositionshallbesuchas tobeable tosafelycarry
the full dead load of the slab, beamorarch asthecase
maybe tOlether withanyliveload likely to occur
duringcuringorfurtherconstruction.
11.3.3Wheretheshapeof theelementis suchthatthe
formworkhasre-entrantangles,theformworkshallbe
removedas soonaspossibleaftertheconcretehasset,
to avoidshrinkage cracking occurring duetothe
restraintimposed.
+12
_ 6mm
+50
mm
-12
0.02timesthe
width
ofthefoot
ing in thedirec
tionofdeviation
butnotmorethan
SOmm
±
o.ostimesthe
specified thick
ness
2)
Eccentricity
3)Thickness
a)Deviationfromspecified
dimensionsofcross-section
ofcolumns
aadbeams
b)Deviationfromdimensions
offootinss
1)
Dimensio.inplan
2118818/07-5
2S
IS456:2000
12.~~PlacingofRelnforcement
Rough handling, shock loading (prior to embedment)
andthedroppingofreinforcementfroma heightshould
be avoided. Reinforcement should hesecuredagainst
displacement outside the specified
limits.
12.3.1Toleranceson Placing
(~fReinforcement
Unlessotherwisespecifiedbyengineer-in-charge,the
reinforcement shall he placed withinthefollowing
tolerances:
orstraightcnedwithoutthe approval ofengineer-in
charge.
Barbendingschedulesshall bepreparedfor all
reinforcement work.
J2.2 Allreinforcementshallbeplacedandmaintained
in thepositionshown in the drawingsbyprovidingpropercover blocks, spacers, supporting bars, etc.
12.2.1Crossingbars should not be lack-weldedfor
assemblyofreinforcementunlesspermitted by
engineer-in-charge.
t2.3~2ToleranceforCover
Unlessspecifiedotherwise,actual concrete cover
should not deviate from the required nominal cover
+10
by 0
mrn,
Nominal
coveras given in 26.4.1 shouldbespecified
toall steel reinforcementincluding links. Spacers
between
thelinks (or thebarswhere no links exist)andthe formworkshouldbe of the same nominal size
as the nominal cover.
Spacers,chairsandothersupportsdetailedon
drawings,togetherwithsuchothersupportsas
mayhenecessary,shouldbeusedtomaintainthe
specitiednominal cover to thesteelreinforcement.
Spacers
orchairs
shouldbe placed atamaximum
spacingofIm and closer spacingmaysometimesbe
necessary.
Spacers,coverblocksshouldheofconcreteofsame
strength or PVC.
1.2.4WeldedJointsor
MechanicalConnections
Weldedjointsormechanicalconnectionsin
reinforcement
maybe
usedbutinallcasesofimportant
connections,testsshallhemade to prove that thejoints
areof the full strength of bars connected.Weldingof
reinforcements shall be done in accordance with the
recommendations of IS 2751 and IS 94
J7.
12.5Where reinforcement bars upto 12 mm for high
strengthdeformedsteel barsand up to 16mm formild
a)foreffectivedepth 200nun
orless
b)for effectivedepthmorethan
200mm
±10nun
±15mm
steelbarsarebent.aside at constructionjointsana
afterwards bent backintotheir original positions. care
should
betaken to ensure that at no time is the radius
of the bend
Jessthan 4 bar diameters for plain mild
steel or 6 bar diameters for deformed bars, Care shall
also be
takenwhen bending
hackbars, to ensure that
the concrete around the bar is not damaged
beyond
the band.
12.6 Reinforcementshould
beplaced and tied in such
awaythatconcreteplacementbepossiblewithout
segregationof themix. Reinforcementplacingshould
allow compactionbyimmersion vibrator. Within the
concrete mass,
differenttypesofmetalincont.act
should
beavoidedtoensurethatbimetalcorrosiondoes
nott.akeplace,
13TRANSPORTING,
PLACING,
COMPACTI'()NANDCURING
1.3.1TransportingandHandling
Aftermixing,
concreteshall betransported tothe
formworkas rapidlyaspossiblebymethods whichwill
prevent the segregationOfJossofanyof the ingredients
oringressofforeignmatter or water andmaintaining
(herequired workability
13.1.1 DuringhoiOfcoldweather.concreteshallbe
transportedindeepcontainers. Othersuitablemethods
toreducethe loss of waterhyevaporationin hot
weather and heat loss
incold weathermayalsobeadopted.
13.2Placing
TIleconcreteshallhedepositedasnearlyaspracticable
in its final
position toavoid rehandling. The concrete
shall
heplacedandcompactedhefore initialsettingof
concrete commences and should not be subsequently
disturbed.Methodsofplacing should besuch as
toprecludescgreg.rtion. Care should be taken to
avoid displacement ofreinforcementormovement
of Iorrnwork . Asageneralguidance,the maxi ...
mum permissible free fall ofconcretemaybe taken
as1.5Ill.
13.3COInpaction
Concreteshouldhe thoroughly compacted andfully
worked around the reinforcement,aroundembedded
fixturesandintocornersofthefonnwork.
13.3.1 Concrete shall
becompacted using mechanical
vibrators
complying withIS
2505,IS 2506. IS 2514
andIS 4656. Over vibration and under vibration of
concreteareharmfuland shouldbeavoided.Vibration
of very wetmixesshould also he avoided.
Whenevervibrationhasto be appliedexternally,the
design of formwork and the disposition of vibrators
shouldreceivespecialconsiderationto ensure efficient
compaction and to avoid surface
blemishes.
26
12.~~PlacingofRelnforcement
Rough handling, shock loading (prior to embedment)
andthedroppingofreinforcementfroma heightshould
be avoided. Reinforcement should hesecuredagainst
displacement outside the specified
limits.
12.3.1Toleranceson Placing
(~fReinforcement
Unlessotherwisespecifiedbyengineer-in-charge,the
reinforcement shall he placed withinthefollowing
tolerances:
orstraightcnedwithoutthe approval ofengineer-in
charge.
Barbendingschedulesshall bepreparedfor all
reinforcement work.
J2.2 Allreinforcementshallbeplacedandmaintained
in thepositionshown in the drawingsbyprovidingpropercover blocks, spacers, supporting bars, etc.
12.2.1Crossingbars should not be lack-weldedfor
assemblyofreinforcementunlesspermitted by
engineer-in-charge.
t2.3~2ToleranceforCover
Unlessspecifiedotherwise,actual concrete cover
should not deviate from the required nominal cover
+10
by 0
mrn,
Nominal
coveras given in 26.4.1 shouldbespecified
toall steel reinforcementincluding links. Spacers
between
thelinks (or thebarswhere no links exist)andthe formworkshouldbe of the same nominal size
as the nominal cover.
Spacers,chairsandothersupportsdetailedon
drawings,togetherwithsuchothersupportsas
mayhenecessary,shouldbeusedtomaintainthe
specitiednominal cover to thesteelreinforcement.
Spacers
orchairs
shouldbe placed atamaximum
spacingofIm and closer spacingmaysometimesbe
necessary.
Spacers,coverblocksshouldheofconcreteofsame
strength or PVC.
1.2.4WeldedJointsor
MechanicalConnections
Weldedjointsormechanicalconnectionsin
reinforcement
maybe
usedbutinallcasesofimportant
connections,testsshallhemade to prove that thejoints
areof the full strength of bars connected.Weldingof
reinforcements shall be done in accordance with the
recommendations of IS 2751 and IS 94
J7.
12.5Where reinforcement bars upto 12 mm for high
strengthdeformedsteel barsand up to 16mm formild
a)foreffectivedepth 200nun
orless
b)for effectivedepthmorethan
200mm
±10nun
±15mm
steelbarsarebent.aside at constructionjointsana
afterwards bent backintotheir original positions. care
should
betaken to ensure that at no time is the radius
of the bend
Jessthan 4 bar diameters for plain mild
steel or 6 bar diameters for deformed bars, Care shall
also be
takenwhen bending
hackbars, to ensure that
the concrete around the bar is not damaged
beyond
the band.
12.6 Reinforcementshould
beplaced and tied in such
awaythatconcreteplacementbepossiblewithout
segregationof themix. Reinforcementplacingshould
allow compactionbyimmersion vibrator. Within the
concrete mass,
differenttypesofmetalincont.act
should
beavoidedtoensurethatbimetalcorrosiondoes
nott.akeplace,
13TRANSPORTING,
PLACING,
COMPACTI'()NANDCURING
1.3.1TransportingandHandling
Aftermixing,
concreteshall betransported tothe
formworkas rapidlyaspossiblebymethods whichwill
prevent the segregationOfJossofanyof the ingredients
oringressofforeignmatter or water andmaintaining
(herequired workability
13.1.1 DuringhoiOfcoldweather.concreteshallbe
transportedindeepcontainers. Othersuitablemethods
toreducethe loss of waterhyevaporationin hot
weather and heat loss
incold weathermayalsobeadopted.
13.2Placing
TIleconcreteshallhedepositedasnearlyaspracticable
in its final
position toavoid rehandling. The concrete
shall
heplacedandcompactedhefore initialsettingof
concrete commences and should not be subsequently
disturbed.Methodsofplacing should besuch as
toprecludescgreg.rtion. Care should be taken to
avoid displacement ofreinforcementormovement
of Iorrnwork . Asageneralguidance,the maxi ...
mum permissible free fall ofconcretemaybe taken
as1.5Ill.
13.3COInpaction
Concreteshouldhe thoroughly compacted andfully
worked around the reinforcement,aroundembedded
fixturesandintocornersofthefonnwork.
13.3.1 Concrete shall
becompacted using mechanical
vibrators
complying withIS
2505,IS 2506. IS 2514
andIS 4656. Over vibration and under vibration of
concreteareharmfuland shouldbeavoided.Vibration
of very wetmixesshould also he avoided.
Whenevervibrationhasto be appliedexternally,the
design of formwork and the disposition of vibrators
shouldreceivespecialconsiderationto ensure efficient
compaction and to avoid surface
blemishes.
26
13.4ConstMlttionJointsandColdJoints
Joints are a common source of weaknessand,therefore,
itis desirable to avoid them. If this is notpossible.
their number shallbeminimized. Concreting shallbe
carriedoutcontinuouslyuptoconstruction joints,
theposition
andarrangementof which shall be
indicated by the designer.
Constructionjoints should
compJywithlS11817.
Constructionjointsshall beplacedataccessible
locations to permit cleaning out of laitance, cement
slurry
andunsound
concrete,in ordertocreaterough/
unevensurface.It is recommendedto cleanout laitance
andcement slurryhyusing wire brush on thesurface
of joint immediatelyafterinitial setting of concrete
and
tocleanout
thesame immediatelythereafter.The
preparedsurfaceshouldbeinacleansaturated surface
drycondition when fresh concreteisplaced.againstit.
Inthecaseofconstructionjointsatlocations where
the previous
pourhasbeen
castagainstshuttering the
recommendedmethodofobtaininga roughsurfacefor
thepreviously pouredconcreteis toexposethe
aggregatewith,1highpressure waterJetoranyother
appropriate
means.
Freshconcreteshouldbethoroughlyvibratednear
constructionjointssothatmortarfromthenewconcrete
flows between largeaggregatesanddevelop proper
bond with old concrete.
WherehighshearresistanceISrequiredat the
constructionjoints. shearkeys"layheprovided.
Sprayedcuringmembranesandreleaseagentsshould
bethoroughly removedfromjoint surfaces.
13.5(:urin~
Curingistheprocess ofpreventingthe Jossofmoisture
from theconcretewhilstmaintainingasatisfactory
temperature regime.Thepreventionof moistureloss
from theconcreteispanicularly importantifthewater
cement ratio
ISlow,ifthecementhas a high rate of
strengthdevelopment,iftheconcretecontains
granulatedblastfurnaceslag orpulverised
fuelash.
TIlecuringregimeshouldalsopreventthe.development
ofhigh temperature gradients within the concrete.
Therateofstrengthdevelopmentatearlyagesof
concretemadewithsupersulphatedcementis
significantlyreducedat"lowertemperatures.
Supersulphated cementconcreteis seriously affected
byinadequate curing andthesurface hastobe kept
moist foratleastseven days.
13.5.1 Moist Curing
Exposedsurfacesofconcreteshallbekept
continuously in a dampOfwet conditionbypending
orbycovering with a layer of sacking,canvas,hessian
or similar materials andkeptconstantly wet for at least
seven
daysfrom
thedate of placing concrete in case
IS456:2000
ofordinaryPortlandCementandat least 10dayswhere
mineraladmixturesor blendedcements are used. The
period of
curingshallnotbeless thanJ0daysfor
concreteexposedtodryandhotweatherconditions.
In the case of concrete wheremineraladmixturesor
blendedcementsareused,itisrecommendedthat
above minimum periods
maybeextended to 14days.
13.5.2
Membrane(..'uring
Approved curing compoundsmaybe used in lieu of
moist curing with
thepermissionof theengineer..in
charge.Suchcompoundsshall beappliedtoallexposed
surfacesof the concrete as soon aspossibleafter the
concrete has set.Impermeable membranessuch as
polyethylenesheeting covering closelytheconcrete
surfacemayalsobeused toprovideeffectivebarrier
againstevaporation.
13.5.3For the concretecontaining Portland pozzolana
cement, Portland slag
cement ormineraladmixture,
period of curingmay
beincreased.
13.6Supervision
Itisexceedinglydifficultandcostlytoalterconcrete
once placed. Hence, constant and strict supervision of
all the items of the construction is necessary during
the progress of the work, including the proportioning
andmixing of the concrete. Supervision is alsoof
extreme importance to check the reinforcement and
itsplacing beforebeing covered.
13.6.1Before anyimportantoperation.suchas
concretingor strippingofthefonnworkis started,
adequatenotice shall begiyentotheconstruction
supervisor.
14CONCRETING UNDERSPECIAL
.
(~ONDITIONS
14.1WorkinExtremeWeatherConditions
During hotorcold weather, the concretingshouldbe
doneaspertheproceduresetoutinIS7861
(Part1)orIS 7861(Part2).
14.2Under-WaterCon~retinl
14.ZL1 Whenitis necessary to deposit concrete under
water,themethods.equipment,materialsand
proportionsofthemixtobeusedshallbesubmittedto
and approvedbytheengineer-in-chargebefore the
workis started.
14.2.2 Under-water
concreteshouldhavea slump
recommended in 7.1. The
water-cementratio shall not
exceed 0 6 and
mayneed tobesmaller, depending on
the grade of concrete or the type of chemical attack.
Foraggregates of 40 rom maximum particle size, the
cement content
shallbe atleast350kg/m'of concrete.
14.1.3Coffer-dams orformsshallbesufficientlytight
27
Joints are a common source of weaknessand,therefore,
itis desirable to avoid them. If this is notpossible.
their number shallbeminimized. Concreting shallbe
carriedoutcontinuouslyuptoconstruction joints,
theposition
andarrangementof which shall be
indicated by the designer.
Constructionjoints should
compJywithlS11817.
Constructionjointsshall beplacedataccessible
locations to permit cleaning out of laitance, cement
slurry
andunsound
concrete,in ordertocreaterough/
unevensurface.It is recommendedto cleanout laitance
andcement slurryhyusing wire brush on thesurface
of joint immediatelyafterinitial setting of concrete
and
tocleanout
thesame immediatelythereafter.The
preparedsurfaceshouldbeinacleansaturated surface
drycondition when fresh concreteisplaced.againstit.
Inthecaseofconstructionjointsatlocations where
the previous
pourhasbeen
castagainstshuttering the
recommendedmethodofobtaininga roughsurfacefor
thepreviously pouredconcreteis toexposethe
aggregatewith,1highpressure waterJetoranyother
appropriate
means.
Freshconcreteshouldbethoroughlyvibratednear
constructionjointssothatmortarfromthenewconcrete
flows between largeaggregatesanddevelop proper
bond with old concrete.
WherehighshearresistanceISrequiredat the
constructionjoints. shearkeys"layheprovided.
Sprayedcuringmembranesandreleaseagentsshould
bethoroughly removedfromjoint surfaces.
13.5(:urin~
Curingistheprocess ofpreventingthe Jossofmoisture
from theconcretewhilstmaintainingasatisfactory
temperature regime.Thepreventionof moistureloss
from theconcreteispanicularly importantifthewater
cement ratio
ISlow,ifthecementhas a high rate of
strengthdevelopment,iftheconcretecontains
granulatedblastfurnaceslag orpulverised
fuelash.
TIlecuringregimeshouldalsopreventthe.development
ofhigh temperature gradients within the concrete.
Therateofstrengthdevelopmentatearlyagesof
concretemadewithsupersulphatedcementis
significantlyreducedat"lowertemperatures.
Supersulphated cementconcreteis seriously affected
byinadequate curing andthesurface hastobe kept
moist foratleastseven days.
13.5.1 Moist Curing
Exposedsurfacesofconcreteshallbekept
continuously in a dampOfwet conditionbypending
orbycovering with a layer of sacking,canvas,hessian
or similar materials andkeptconstantly wet for at least
seven
daysfrom
thedate of placing concrete in case
IS456:2000
ofordinaryPortlandCementandat least 10dayswhere
mineraladmixturesor blendedcements are used. The
period of
curingshallnotbeless thanJ0daysfor
concreteexposedtodryandhotweatherconditions.
In the case of concrete wheremineraladmixturesor
blendedcementsareused,itisrecommendedthat
above minimum periods
maybeextended to 14days.
13.5.2
Membrane(..'uring
Approved curing compoundsmaybe used in lieu of
moist curing with
thepermissionof theengineer..in
charge.Suchcompoundsshall beappliedtoallexposed
surfacesof the concrete as soon aspossibleafter the
concrete has set.Impermeable membranessuch as
polyethylenesheeting covering closelytheconcrete
surfacemayalsobeused toprovideeffectivebarrier
againstevaporation.
13.5.3For the concretecontaining Portland pozzolana
cement, Portland slag
cement ormineraladmixture,
period of curingmay
beincreased.
13.6Supervision
Itisexceedinglydifficultandcostlytoalterconcrete
once placed. Hence, constant and strict supervision of
all the items of the construction is necessary during
the progress of the work, including the proportioning
andmixing of the concrete. Supervision is alsoof
extreme importance to check the reinforcement and
itsplacing beforebeing covered.
13.6.1Before anyimportantoperation.suchas
concretingor strippingofthefonnworkis started,
adequatenotice shall begiyentotheconstruction
supervisor.
14CONCRETING UNDERSPECIAL
.
(~ONDITIONS
14.1WorkinExtremeWeatherConditions
During hotorcold weather, the concretingshouldbe
doneaspertheproceduresetoutinIS7861
(Part1)orIS 7861(Part2).
14.2Under-WaterCon~retinl
14.ZL1 Whenitis necessary to deposit concrete under
water,themethods.equipment,materialsand
proportionsofthemixtobeusedshallbesubmittedto
and approvedbytheengineer-in-chargebefore the
workis started.
14.2.2 Under-water
concreteshouldhavea slump
recommended in 7.1. The
water-cementratio shall not
exceed 0 6 and
mayneed tobesmaller, depending on
the grade of concrete or the type of chemical attack.
Foraggregates of 40 rom maximum particle size, the
cement content
shallbe atleast350kg/m'of concrete.
14.1.3Coffer-dams orformsshallbesufficientlytight
27
IS456:2000
to ensure still water ifpracticable. andinanycueto
reducethe flowof waterto lessthan3m1minthroup
thespaceinto which concrete is tobedeposited.
Coffer-damsorfonns instillwatershallbesufficiently
tight to prevent loss of mortar throughthewalls.
De-watering by pumping shall not
bedone while
concreteis beingplacedor until24 hthereafter.
14.2.4Concretecastunderwatershouldnotfall
freely
through the water.Otherwiseitmay
beleachedand
becomesegregated. Concrete shall be deposited
continuouslyuntilit is broughttotherequiredheight.
Whiledepositing.the topsurfaceshallbekeptasnearly
levelas possibleandthefonnationof seamsavoided.
Themethodstobeusedfordepositingconcreteunder
watershallbeone of thefollowing:
a)
Tremie-
Theconcreteisplacedthroupvertical
pipesthe lowerend of whichisalwaysinserted
sufficientlydeep into the concrete which
has
beenplaced previously buthasnotset. The
concrete emerging from the pipe
pushesthe
materialthathas
alreadybeenplacedto theside
andupwardsand thusdoes
notcomeintodirect
contactwithwater.
When concreteistobedepositedunder water
by
meansoftremie,the topsectionofthetremie
shallbeahopper
largeenoughtoholdoneentire
batch of the mix or the entire contents the
transporting
bucket,ifany.
Thetremiepipeshall
benot less than 200 mm in diameterand shall
belargeenoughtoallowa freeflowofconcrete
and strong enough to withstand the external
pressureof thewaterin whichitissuspended,
even
ifa
panialvacuumdevelopsinsidethepipe.
Preferably,flangedsteel pipe ofadequate
strengthforthejob shouldbeused.Aseparate
lifting
deviceshallbeprovidedforeach
tremie
pipewith itshopper at the upper end.Unless
the lowerendofthe pipe isequippedwith an
approvedautomaticcheckvalve, theupperend
ofthepipe shallbepluggedwitha waddingof
the gunny sackingor otherapprovedmaterial
beforedelivering
theconcreteto
thetromiepipe
throughthe
hopper,sothat
whentheconcreteis
forceddownfromthehoppertothepipe,itwill
force the plug (and along with
itanywater in
the pipe) down the pipe and out of
thebottom
end. thusestablishingacontinuousstream of
concrete.
It willbe
necessarytoraiseslowlythe
tremie in order tocauseauniformflow of the
concrete,but thetremieshallnotbeemptied10
that waterentersthepipe.At all timesafterthe
placingof concrete is started and until all the
concrete isplaced,the lowerend ofthettemie
pipeshallbebelowthetopsurfaceoftheplastic
concrete.This.will cause theconcreteto build
up from below insteadof
flowingout
overthe
28
.urface,andthusavoidformetionoflaitance
layors.Ifthocluqointhotremieis10ltwhile
depositin,.thotromioshallbonaisedIlxlved1e
concretesurface,andunloss_04byIc~k
valvo,itshallberc-plulledatthotopend,as••
thebeginninl.beforerefl11inlfordcpositin,
concrete.
b)Directplactmentwithpumps-Asin thecase
of thetremiemethod,thoverticalend pieceof
the
pipelineisalways
insertedsufficientlydeep
intothepreviooslycastconcreteandshouldnot
movetotltesideduringpumping.
c)Dmpbouombucket-Thetopofthebucketshall
bocoveredwithacanvasflap.Thebottomdoors
shallopenfreelydownwvdandoutwardwhen
tripped.Thebucketshallbo(diedcompletelyand
loweredslowlytoavoidbackwaah.Thebottom
doorsshallnotbeopeneduntilthobucketrests
onthesurfaceuponwhichtheconcretoistobe
deposited and whendtscharged,shallbe
withdrawnslowlyuntilwellabovetheconcrete,
d)Bags-Bagsof at least 0.028 m]capacityof
juteorothercoarsecloth shallbefilled about
two-thirdsfullofconcrete,thespareendturned
underso
that
baaissquareendedandsecurely
tied.Theyshallbeplacedcarefullyin header
andstretcher
coursesso thatthewholemassis
interlocked.Bagsusedforthispurposeshall be
freefromdeleteriousmaterials.
e)Grouting-Aseries of roundcages made from
SOmmmeshof 6 mmsteelandextendingover
thefullheishttobeconcretedshall beprepared
and
laidvorticallyovertheareatobeconcreted
sothatthodistancebetweencentresofthecases
and also tothefacesofthe concreteshall not
exceedonemetre.Stoneaggregateof not less
thanSOmmnormorethan200mmsizeshallbe
depositedoutsidethestoolcagesoverthefull
areaandheightto
be
concretedwithduecareto
preventdisplacement
of
thecages.
A stable 1:2cement-sandgroutwith awater
cementratioof notlossthan0.6andnot marc
than0.8shallbepreparedinamechanicalmixer
andsentdownunderpressure(about0.2N/inm
2
)
throulh 38to
50nundiameterpipestenninating
intosteelcages,aboutSOmmabovethebottom
of theconcrete.Asthe&rautio,proceeds,the
pipeshallberaisedaraduallyup to a heiaht of
notmorethan6 000nunaboveitsstarlin, level
afterwhichitmaybewithdrawnandpl,acodinto
thenoxtcale forfurthergroutiolbythesame
procedure.
AfterIfOUtinlthewholeareafor aheishtof
about 600 mm, thesameoperation shallbe
repeated,ifnecessary.forthenextlayer of
to ensure still water ifpracticable. andinanycueto
reducethe flowof waterto lessthan3m1minthroup
thespaceinto which concrete is tobedeposited.
Coffer-damsorfonns instillwatershallbesufficiently
tight to prevent loss of mortar throughthewalls.
De-watering by pumping shall not
bedone while
concreteis beingplacedor until24 hthereafter.
14.2.4Concretecastunderwatershouldnotfall
freely
through the water.Otherwiseitmay
beleachedand
becomesegregated. Concrete shall be deposited
continuouslyuntilit is broughttotherequiredheight.
Whiledepositing.the topsurfaceshallbekeptasnearly
levelas possibleandthefonnationof seamsavoided.
Themethodstobeusedfordepositingconcreteunder
watershallbeone of thefollowing:
a)
Tremie-
Theconcreteisplacedthroupvertical
pipesthe lowerend of whichisalwaysinserted
sufficientlydeep into the concrete which
has
beenplaced previously buthasnotset. The
concrete emerging from the pipe
pushesthe
materialthathas
alreadybeenplacedto theside
andupwardsand thusdoes
notcomeintodirect
contactwithwater.
When concreteistobedepositedunder water
by
meansoftremie,the topsectionofthetremie
shallbeahopper
largeenoughtoholdoneentire
batch of the mix or the entire contents the
transporting
bucket,ifany.
Thetremiepipeshall
benot less than 200 mm in diameterand shall
belargeenoughtoallowa freeflowofconcrete
and strong enough to withstand the external
pressureof thewaterin whichitissuspended,
even
ifa
panialvacuumdevelopsinsidethepipe.
Preferably,flangedsteel pipe ofadequate
strengthforthejob shouldbeused.Aseparate
lifting
deviceshallbeprovidedforeach
tremie
pipewith itshopper at the upper end.Unless
the lowerendofthe pipe isequippedwith an
approvedautomaticcheckvalve, theupperend
ofthepipe shallbepluggedwitha waddingof
the gunny sackingor otherapprovedmaterial
beforedelivering
theconcreteto
thetromiepipe
throughthe
hopper,sothat
whentheconcreteis
forceddownfromthehoppertothepipe,itwill
force the plug (and along with
itanywater in
the pipe) down the pipe and out of
thebottom
end. thusestablishingacontinuousstream of
concrete.
It willbe
necessarytoraiseslowlythe
tremie in order tocauseauniformflow of the
concrete,but thetremieshallnotbeemptied10
that waterentersthepipe.At all timesafterthe
placingof concrete is started and until all the
concrete isplaced,the lowerend ofthettemie
pipeshallbebelowthetopsurfaceoftheplastic
concrete.This.will cause theconcreteto build
up from below insteadof
flowingout
overthe
28
.urface,andthusavoidformetionoflaitance
layors.Ifthocluqointhotremieis10ltwhile
depositin,.thotromioshallbonaisedIlxlved1e
concretesurface,andunloss_04byIc~k
valvo,itshallberc-plulledatthotopend,as••
thebeginninl.beforerefl11inlfordcpositin,
concrete.
b)Directplactmentwithpumps-Asin thecase
of thetremiemethod,thoverticalend pieceof
the
pipelineisalways
insertedsufficientlydeep
intothepreviooslycastconcreteandshouldnot
movetotltesideduringpumping.
c)Dmpbouombucket-Thetopofthebucketshall
bocoveredwithacanvasflap.Thebottomdoors
shallopenfreelydownwvdandoutwardwhen
tripped.Thebucketshallbo(diedcompletelyand
loweredslowlytoavoidbackwaah.Thebottom
doorsshallnotbeopeneduntilthobucketrests
onthesurfaceuponwhichtheconcretoistobe
deposited and whendtscharged,shallbe
withdrawnslowlyuntilwellabovetheconcrete,
d)Bags-Bagsof at least 0.028 m]capacityof
juteorothercoarsecloth shallbefilled about
two-thirdsfullofconcrete,thespareendturned
underso
that
baaissquareendedandsecurely
tied.Theyshallbeplacedcarefullyin header
andstretcher
coursesso thatthewholemassis
interlocked.Bagsusedforthispurposeshall be
freefromdeleteriousmaterials.
e)Grouting-Aseries of roundcages made from
SOmmmeshof 6 mmsteelandextendingover
thefullheishttobeconcretedshall beprepared
and
laidvorticallyovertheareatobeconcreted
sothatthodistancebetweencentresofthecases
and also tothefacesofthe concreteshall not
exceedonemetre.Stoneaggregateof not less
thanSOmmnormorethan200mmsizeshallbe
depositedoutsidethestoolcagesoverthefull
areaandheightto
be
concretedwithduecareto
preventdisplacement
of
thecages.
A stable 1:2cement-sandgroutwith awater
cementratioof notlossthan0.6andnot marc
than0.8shallbepreparedinamechanicalmixer
andsentdownunderpressure(about0.2N/inm
2
)
throulh 38to
50nundiameterpipestenninating
intosteelcages,aboutSOmmabovethebottom
of theconcrete.Asthe&rautio,proceeds,the
pipeshallberaisedaraduallyup to a heiaht of
notmorethan6 000nunaboveitsstarlin, level
afterwhichitmaybewithdrawnandpl,acodinto
thenoxtcale forfurthergroutiolbythesame
procedure.
AfterIfOUtinlthewholeareafor aheishtof
about 600 mm, thesameoperation shallbe
repeated,ifnecessary.forthenextlayer of
I·5
6 -IS
16 - 30
31 - 50
51and above
600
mmandsoon.
Theamount of grouttobesent downshallbe
sufficienttofillallthevoidswhichmaybeeither
asc~rtained orassumedas55percentof the
volumetobeconcreted.
14.2.5Tominimizetheformulationoflaitance,great
care shallbeexercisednot todisturbthe concreteas
far as possible while it is beingdeposited.
15SAMPLINGANDSTRENGTHOF
DESIGNEDCONCRETEMIX
15.1General
Samples from fresh concrete shall be takenasper
IS 1199and cubes shall
bemade, curedandtestedat
28daysinaccordancewithIS
S16.
15.1.1 Inorder to get arelativelyquickeridea of the
quality ofconcrete,optional tests on beams for
modulus
ofruptureat72±2 h or at 7 days, or
compressivestrength
tests at7 days maybecarried
out in addition to 28 dayscompressivestrengthtest.
For this purposethe valuesshouldbe
arrivedat based
onactualtesting. In allcases,the28dayscompressive
strengthspecifiedinTable2 shallalone
bethecriterion
for acceptanceor rejectionof theconcrete.
15.1FrequencyofSampling
15.2.1 SamplingProcedure
Arandomsampling procedureshallbeadoptedto
ensurethateachconcretebatchshallhaveareasonable
chance of being tested that is, thesamplingshould be
spreadoverthe entireperiodofconcretingand cover
all mixing units. .
15.2.2Frequency
The minimumfrequencyof samplingof concrete of
each grade shall
beiDaccordancewiththe following:
QuantityofConcrete in
theNumberofSamples
Work,m'
1
2
3
4
4 plus one
additionalsample
foreachadditional
50m'orpartthereof
NOm-Atleostone sample shallbetakenfromeachshift.
Whereconcreteis producedatcontinuousproductionunit,such
asready-mixedconcreteplant,frequencyof'samplinglnaybe
agreeduponmutuallybysuppliersandpurchasers.
15.3Test Specimen
Three test specimens shallbemade for each sample
L~456:1000
fortestingat28days.Additionalsamplesmaybe
requiredfor variouspurposessuch as todeterminethe
strengthof concreteat
7daysor at the timeof striking
the
formwork,or to determinethe duration of
curing.
or to checkthe testingerror.Additionalsamples may
alsoberequiredfortestingsamplescuredby
accelerated methods as described in IS 9103. The
specimenshall
betested as describedin IS
S16.
15.4TestResultsofSample
The testresultsof the sample shallbethe average of
the strength of three specimens. The
individual
variationshould not bemorethan±lSpercent of the
average.Ifmore,the
testresult.~of thesampleareinvalid.
16ACCEPTANCECRITERIA
16.1CompressiveStreoath
Theconcrete shallbedeemedtocomply with the
strengthrequirementswhen
boththefollowing
conditionare met:
a) The mean
strengthdeterminedfrom anygroup
of fourconsecutivetest results compiles with
theappropriatelimits in col 2 of Table 11.
b) Any individual test resultcomplieswiththe
appropriatelimits in col 3 of Table I).
16.2FlexuralStrength
Whenboth thefollowingconditionsaremet"the
concretecomplieswiththespecifiedflexuralstrength.
a)The mean strengthdetermined fromanygroup
of four consecutive test results exceeds the
specified
characteristicstrengthbyat least 0.3
N/mn1
2
•
b) The strengthdeterminedfrom anytest result is
not less thanthespecifiedcharacteristicstrength
less 0.3N/mm
1
•
16.3
QuantityofConcreteRepresentedby
StrengthTeatResults
The quantity of concreterepresented
bya group of
fourconsecutivetest resultsshall includethe batches
from which .the first and last samples were taken
togetherwithallinterveningbatches.
For theindividualtest resultrequirementsgiven in
col 2 of Table II or in item (b) of
16.2,only the
particularbatchfromwhichthesamplewastakenshall
beat risk.
Where the mean rate of samplingis notspecifiedthe
maximumquantityof concrete that four consecutive
test
resultsrepresentshallbe limitedto 60m'.
16.4
Iftheconcreteisdeemednot to complypersuant
to16.3.thestructuraladequacyofthepartsaffected
shall beinvestigated
(see17)andanyconsequential
action
asneededshallbetaken.
29
6 -IS
16 - 30
31 - 50
51and above
600
mmandsoon.
Theamount of grouttobesent downshallbe
sufficienttofillallthevoidswhichmaybeeither
asc~rtained orassumedas55percentof the
volumetobeconcreted.
14.2.5Tominimizetheformulationoflaitance,great
care shallbeexercisednot todisturbthe concreteas
far as possible while it is beingdeposited.
15SAMPLINGANDSTRENGTHOF
DESIGNEDCONCRETEMIX
15.1General
Samples from fresh concrete shall be takenasper
IS 1199and cubes shall
bemade, curedandtestedat
28daysinaccordancewithIS
S16.
15.1.1 Inorder to get arelativelyquickeridea of the
quality ofconcrete,optional tests on beams for
modulus
ofruptureat72±2 h or at 7 days, or
compressivestrength
tests at7 days maybecarried
out in addition to 28 dayscompressivestrengthtest.
For this purposethe valuesshouldbe
arrivedat based
onactualtesting. In allcases,the28dayscompressive
strengthspecifiedinTable2 shallalone
bethecriterion
for acceptanceor rejectionof theconcrete.
15.1FrequencyofSampling
15.2.1 SamplingProcedure
Arandomsampling procedureshallbeadoptedto
ensurethateachconcretebatchshallhaveareasonable
chance of being tested that is, thesamplingshould be
spreadoverthe entireperiodofconcretingand cover
all mixing units. .
15.2.2Frequency
The minimumfrequencyof samplingof concrete of
each grade shall
beiDaccordancewiththe following:
QuantityofConcrete in
theNumberofSamples
Work,m'
1
2
3
4
4 plus one
additionalsample
foreachadditional
50m'orpartthereof
NOm-Atleostone sample shallbetakenfromeachshift.
Whereconcreteis producedatcontinuousproductionunit,such
asready-mixedconcreteplant,frequencyof'samplinglnaybe
agreeduponmutuallybysuppliersandpurchasers.
15.3Test Specimen
Three test specimens shallbemade for each sample
L~456:1000
fortestingat28days.Additionalsamplesmaybe
requiredfor variouspurposessuch as todeterminethe
strengthof concreteat
7daysor at the timeof striking
the
formwork,or to determinethe duration of
curing.
or to checkthe testingerror.Additionalsamples may
alsoberequiredfortestingsamplescuredby
accelerated methods as described in IS 9103. The
specimenshall
betested as describedin IS
S16.
15.4TestResultsofSample
The testresultsof the sample shallbethe average of
the strength of three specimens. The
individual
variationshould not bemorethan±lSpercent of the
average.Ifmore,the
testresult.~of thesampleareinvalid.
16ACCEPTANCECRITERIA
16.1CompressiveStreoath
Theconcrete shallbedeemedtocomply with the
strengthrequirementswhen
boththefollowing
conditionare met:
a) The mean
strengthdeterminedfrom anygroup
of fourconsecutivetest results compiles with
theappropriatelimits in col 2 of Table 11.
b) Any individual test resultcomplieswiththe
appropriatelimits in col 3 of Table I).
16.2FlexuralStrength
Whenboth thefollowingconditionsaremet"the
concretecomplieswiththespecifiedflexuralstrength.
a)The mean strengthdetermined fromanygroup
of four consecutive test results exceeds the
specified
characteristicstrengthbyat least 0.3
N/mn1
2
•
b) The strengthdeterminedfrom anytest result is
not less thanthespecifiedcharacteristicstrength
less 0.3N/mm
1
•
16.3
QuantityofConcreteRepresentedby
StrengthTeatResults
The quantity of concreterepresented
bya group of
fourconsecutivetest resultsshall includethe batches
from which .the first and last samples were taken
togetherwithallinterveningbatches.
For theindividualtest resultrequirementsgiven in
col 2 of Table II or in item (b) of
16.2,only the
particularbatchfromwhichthesamplewastakenshall
beat risk.
Where the mean rate of samplingis notspecifiedthe
maximumquantityof concrete that four consecutive
test
resultsrepresentshallbe limitedto 60m'.
16.4
Iftheconcreteisdeemednot to complypersuant
to16.3.thestructuraladequacyofthepartsaffected
shall beinvestigated
(see17)andanyconsequential
action
asneededshallbetaken.
29
IS456:2000
16.5Concreteof each grade shall beassessed
separately.
16.6Concrete is liable to be rejected if it is porous
or honey-combed. its placing has been interrupted
without providing a proper construction joint. the
reinforcementhas beendisplacedbeyondthe
tolerances specified. or construction toleranceshave
not been met. However. the hardenedconcrete
may beacceptedaftercarryingoutsuitable
remedialmeasuresto the satisfactionof theengineer
in-charge.
17INSPECTIONANDTESTINGOFSTRU<"'""TURES
17.1Inspection
To ensure that the construction complies with the
design aninspectionprocedure should be set up
coveringmaterials,records.workmanshipand
construction.
17.1.1 Tests should be made onreinforcementand
theconstituentmaterialsofconcreteinaccordancewith
the relevant standards. Whereapplicable,use should
bemade of suitable quality assuranceschemes.
17.1.2 Care should be taken to see that:
a) design and detail arecapableof beingexecuted
to a suitable standard, with dueallowancefor
dimensionaltolerances;
b)thereareclearinstructionsoninspection
standards;
c) there are clearinstructionsonpermissible
deviations;
d) clements critical to workmanship, structural
performance. durability and appearance are
identified;and
e) there is a system to verify that the quality is
satisfactoryinindividual
partsof the structure,
especiallythe criticalones.
17.2Immediatelyafter stripping theforrnwork,all
concreteshallbecarefullyinspectedandanydefective
work or small defects either removed or madegood
beforeconcrete hasthoroughlyhardened.
17.3
Testing
Incase of doubtregardingthe
gradeof concreteused,
eitherdue to poorworkmanship orbasedon resultsof
cube strength tests, compressive strength tests of
concreteon thebasisof
17.4and/orloadtest
(see17.6)
maybecarriedout.
17.4CoreTest
17.4.1 The points from which cores are tobetaken
and the number of cores required shall be at the
discretion of the
engineer-in-chargeand shall be
representative of the whole of concrete concerned.
In no case.however.shall fewer than three cores
be
tested.
17.4.2 Coresshallbepreparedand
testedasdescribed
in IS 516.
17.4.3Concretein the memberrepresentedbya core
test shall be considered acceptable if the average
equivalentcubestrengthof thecoresisequalto at least
85percentof thecubestrengthof thegradeofconcrete
specifiedfor the correspondingage and noindividual
core has a strengthless than
7Spercent.
17.5In case the core test results do not satisfy the
requirement.s of 17.4.3 or where such tests have not
been done, load test
(17.6)mayberesortedto.
17.6
LoadTestsforFlexuralMember
17.6.1 Load tests shouldbecarried outassoonas
Table11CharacteristicCompressive StrengthComplianceRequirement
(Claus~s 16.1and 16.3)
(3)
IndividualTest
ResultsInN1mm
J
II)
Sp«lfted
(;rade
MI~
MeanoftheGroupof
4Non-Onrlapplnl
Consecutive
nsfResultsInNfmm
J
(2)
4!1...+0.825xestablished
standarddeviation(rounded
off toneaJal0.5Nlmm
1
)
or
f
..+3NlmmJ.
whicheverisgreater
M20 ~.f..,+0.82S)(established ~f",~N/mm
1
or standarddeviation(rounded
above off tonealatO.~N/mm
J
)
or
L..+4N/..mr.whichever
is~ter
NOTE-Intheabsenceofestablishedvalueofstandarddeviation.thevaluesJiveninTable8l114ybeassumed.andllttemptshouldbe
l1llIde10obtainresultsof 30sampleslISearlylISpoasibletoambUshdievalueofstandarddeviation.
30
16.5Concreteof each grade shall beassessed
separately.
16.6Concrete is liable to be rejected if it is porous
or honey-combed. its placing has been interrupted
without providing a proper construction joint. the
reinforcementhas beendisplacedbeyondthe
tolerances specified. or construction toleranceshave
not been met. However. the hardenedconcrete
may beacceptedaftercarryingoutsuitable
remedialmeasuresto the satisfactionof theengineer
in-charge.
17INSPECTIONANDTESTINGOFSTRU<"'""TURES
17.1Inspection
To ensure that the construction complies with the
design aninspectionprocedure should be set up
coveringmaterials,records.workmanshipand
construction.
17.1.1 Tests should be made onreinforcementand
theconstituentmaterialsofconcreteinaccordancewith
the relevant standards. Whereapplicable,use should
bemade of suitable quality assuranceschemes.
17.1.2 Care should be taken to see that:
a) design and detail arecapableof beingexecuted
to a suitable standard, with dueallowancefor
dimensionaltolerances;
b)thereareclearinstructionsoninspection
standards;
c) there are clearinstructionsonpermissible
deviations;
d) clements critical to workmanship, structural
performance. durability and appearance are
identified;and
e) there is a system to verify that the quality is
satisfactoryinindividual
partsof the structure,
especiallythe criticalones.
17.2Immediatelyafter stripping theforrnwork,all
concreteshallbecarefullyinspectedandanydefective
work or small defects either removed or madegood
beforeconcrete hasthoroughlyhardened.
17.3
Testing
Incase of doubtregardingthe
gradeof concreteused,
eitherdue to poorworkmanship orbasedon resultsof
cube strength tests, compressive strength tests of
concreteon thebasisof
17.4and/orloadtest
(see17.6)
maybecarriedout.
17.4CoreTest
17.4.1 The points from which cores are tobetaken
and the number of cores required shall be at the
discretion of the
engineer-in-chargeand shall be
representative of the whole of concrete concerned.
In no case.however.shall fewer than three cores
be
tested.
17.4.2 Coresshallbepreparedand
testedasdescribed
in IS 516.
17.4.3Concretein the memberrepresentedbya core
test shall be considered acceptable if the average
equivalentcubestrengthof thecoresisequalto at least
85percentof thecubestrengthof thegradeofconcrete
specifiedfor the correspondingage and noindividual
core has a strengthless than
7Spercent.
17.5In case the core test results do not satisfy the
requirement.s of 17.4.3 or where such tests have not
been done, load test
(17.6)mayberesortedto.
17.6
LoadTestsforFlexuralMember
17.6.1 Load tests shouldbecarried outassoonas
Table11CharacteristicCompressive StrengthComplianceRequirement
(Claus~s 16.1and 16.3)
(3)
IndividualTest
ResultsInN1mm
J
II)
Sp«lfted
(;rade
MI~
MeanoftheGroupof
4Non-Onrlapplnl
Consecutive
nsfResultsInNfmm
J
(2)
4!1...+0.825xestablished
standarddeviation(rounded
off toneaJal0.5Nlmm
1
)
or
f
..+3NlmmJ.
whicheverisgreater
M20 ~.f..,+0.82S)(established ~f",~N/mm
1
or standarddeviation(rounded
above off tonealatO.~N/mm
J
)
or
L..+4N/..mr.whichever
is~ter
NOTE-Intheabsenceofestablishedvalueofstandarddeviation.thevaluesJiveninTable8l114ybeassumed.andllttemptshouldbe
l1llIde10obtainresultsof 30sampleslISearlylISpoasibletoambUshdievalueofstandarddeviation.
30
possibleafterexpiryof28daysfrom the lillie ofplacing
ofconcrete.
17.6.2 The structure shouldhesubjected to aloadequal
tofulldeadloadofthestructure plus1.25tillll'Sthe
imposedloadtoraperiodof24 h and then theunposed
load shall heremoved,
NOTE--·-Dc:adloadincludesselfweightofthestructural
memberspili"weightof finishesandwallsorpartition».Ifany
~l'\consideredin thedesign .
17.6.3Thedeflectiondue toiTJIPOSl~d loadonlyshall
he recorded. If within 24 h of removaloftheimposed
load.thestructuredocs notrecoverat least75percent
ofthedeflection under superimposedload,thetestmay
berepealedafter a lapse of 72 h. If therl~CO\'CI"y isIcs~
thanXOpercent..thestructureshall bedc.eln~d 1ohe
unacceptable.
.7.()...llIrthemaximumdeflectionin111111.shown
during.24hunderload i~lessthan 4()/'~/1.).whereIis
theeffectivespanin m;and1.),theoveralldepthoftlk'
~cclj()n in111111,iti\notncccxs.nyfOItheteL·O\CIV10
hemeasuredandtherecoveryprovi,ion",oft7.tl.~'...,-hall
11
IS45(i:200()
notapply.
17.7Members(1thcrThanFlexuralMembers
Memher-,otherthanflexuralmembersshouldhe
preferablyinvestigatedhyanalysis.
17.HNon-destructiveTests
Non-destructivetests arcused toobtainestimationof
thepropertiesofconcretein thestructure.TIlemethods
adoptedincludeultrasonicpulsevelocity(secISJ33)I
(PariI)Jandreboundhammer [IS13311(Pari 2)L
prnbepcnetrati()n,pull0utand matlJrity.Non
dcstructivctestsprovidealternativestocoretests for
cstirnatiugthe strengthofconcreteinastructure.or
canxupplcmcutthe dataobtained1'1"0111alimited
nUIIIherofcores.Thesemethodsart'basedon
mcusuring aconcreteproperlythaIbearssonic
rl~latic.nshiptostrength,Theaccuracyofthesemethods,
inpart.isdeterminedbythedegreeofcorrelation
h('l\.'t'l'tl~fn..nc~thHndIhephysicalquality1I1CtlSUrl,d
h)th~'nundestructivc texts.
Anvofth\..~"i~mcthodxtna~'he .uloptcd. in whichcuscthe
~H'n ..'I'I~IIH.'l"cnll'ria~h~lllheagreeduponpriortoh'sling.
ofconcrete.
17.6.2 The structure shouldhesubjected to aloadequal
tofulldeadloadofthestructure plus1.25tillll'Sthe
imposedloadtoraperiodof24 h and then theunposed
load shall heremoved,
NOTE--·-Dc:adloadincludesselfweightofthestructural
memberspili"weightof finishesandwallsorpartition».Ifany
~l'\consideredin thedesign .
17.6.3Thedeflectiondue toiTJIPOSl~d loadonlyshall
he recorded. If within 24 h of removaloftheimposed
load.thestructuredocs notrecoverat least75percent
ofthedeflection under superimposedload,thetestmay
berepealedafter a lapse of 72 h. If therl~CO\'CI"y isIcs~
thanXOpercent..thestructureshall bedc.eln~d 1ohe
unacceptable.
.7.()...llIrthemaximumdeflectionin111111.shown
during.24hunderload i~lessthan 4()/'~/1.).whereIis
theeffectivespanin m;and1.),theoveralldepthoftlk'
~cclj()n in111111,iti\notncccxs.nyfOItheteL·O\CIV10
hemeasuredandtherecoveryprovi,ion",oft7.tl.~'...,-hall
11
IS45(i:200()
notapply.
17.7Members(1thcrThanFlexuralMembers
Memher-,otherthanflexuralmembersshouldhe
preferablyinvestigatedhyanalysis.
17.HNon-destructiveTests
Non-destructivetests arcused toobtainestimationof
thepropertiesofconcretein thestructure.TIlemethods
adoptedincludeultrasonicpulsevelocity(secISJ33)I
(PariI)Jandreboundhammer [IS13311(Pari 2)L
prnbepcnetrati()n,pull0utand matlJrity.Non
dcstructivctestsprovidealternativestocoretests for
cstirnatiugthe strengthofconcreteinastructure.or
canxupplcmcutthe dataobtained1'1"0111alimited
nUIIIherofcores.Thesemethodsart'basedon
mcusuring aconcreteproperlythaIbearssonic
rl~latic.nshiptostrength,Theaccuracyofthesemethods,
inpart.isdeterminedbythedegreeofcorrelation
h('l\.'t'l'tl~fn..nc~thHndIhephysicalquality1I1CtlSUrl,d
h)th~'nundestructivc texts.
Anvofth\..~"i~mcthodxtna~'he .uloptcd. in whichcuscthe
~H'n ..'I'I~IIH.'l"cnll'ria~h~lllheagreeduponpriortoh'sling.
IS456:1000
SECTION3GENERALDESIGNCONSIDERATION
18 BASESFORDESIGN
18.1 AimofDesigD
The aim of design is the achievementof an acceptable
probabilitythatstructuresbeingdesignedwillperform
satisfactorilyduringtheir
intendedlife. Withan
appropriate degree of safety, they should sustain all
the loadsand deformationsof
normalconstructionand
use and haveadequatedurabilityandadequate
resistance to the effects of misuse and fire.
18.2Methodsof Design
18.2.1Structureand structuralelementsshallnonnally
bedesigned by Limit State Method. Account should
betakenofacceptedtheories,experimentand
experienceandtheneedtodesignfor durability.
Calculationsalonedo notproducesafe,serviceableand
durable structures. Suitablematerials,qualitycontrol.
adequate detailing and good supervision are equally
important.
18.2.2Where the Limit State Method can not be
conveniently adopted, Working Stress Method(see
Annex B) may be used.
18.2.3DesignBasedonExperimentalBasis
Designsbasedonexperimentalinvestigationson
modelsorfullsizestructureorelementmay be
accepted if they satisfy the primary requirements
of
18.1and subject to experimental details and the
analysis connected therewith being approved
bythe
engineer-in-charge.
18.2.3.1 Where
.the
designis based on experimental
investigationonfullsizestructureorelement,loadtests
shall
be
carriedout to ensure thefollowing:
a) Thestructureshall satisfy the requirementsfor
deflection
(see
23.2)and cracking(see35.3.2)
when subjected to a load for 24 hequalto the
characteristicload multiplied
by ).33Yr'where"(rshallbetakenfromTable 18,forthelimitstate
ofserviceability.If within 24 h of theremoval
of the load, thestructuredoes
not showa
recovery of at least
7Spercentofthemaximum
deflectionshownduringthe24hunder.theload,
the test loading should
berepeated after a lapse
of 72
h.Therecoveryafterthesecond
testshould
beat least7Spercentof themaximumdeflection
shown during thesecondtest.
NOTE-Ifthemaximumdeflectionin mm, shown duriftl
24hunderloadislessthan401
2/D
whereIistheeffectivespan
in m;andDistheoveralldepthofthesectioninrom,iti.not
necessaryforthe~tobemeasured.
b) Thestructureshall have adequatestrenathto
sustainfor24 h,atotalloadequaltothecharac
teristic load multipliedby1.331,whereY,shall
betakenfrom Table 18 forthelimit state of
collapse.
18.3 DurabWty,WorkmanshipaDd~terlall
It is assumed that the quality of concrete, steel and
other materials and of theworkmanship,as verified
byinspections,
isadequatefotsafety.serviceability
anddurability.
18.4
DesllDProcess
Design.includingdesignfordurability,construction
and use in service shouldbeconsideredas awhole.
Therealizationofdesignobjectivesrequires
compliance
with
clearlydefinedstandardsfor
materials,production,workmanship andalso
maintenance
anduse ofstructureinservice.
19LOADS
AND'ORCES
19.1General
Instructuraldesign,accountshallbetakenofthedead.
imposedandwind loads andforces suchasthose
causedbyearthquake.andeffectsduetoshrinkage,
creep,temperature,etc,whereapplicable.
19.2DeadLoads
Dead loads shallbecalculatedon the basis of unit
weightswhichshallbeestablished
takina into
considerationthe materialsspecifiedfor construction.
19.2.1Alternatively,thedead loadsmaybecalculated
onthebasis of unit weights of materialslivenin
IS875(Part 1).Unlessmoreaccuratecalculationsare
warranted, the unit weightsofplainconcrete and
reinforced concrete made with sand and gravel or
crushed natural stone aggregate
maybetakenas
24
kN/m:\and25kN/m
3
respectively.
19.3ImposedLoads,WIndLoadsand SnowLoIds
Imposed loads. wind loads and snow loads shallbe
assumed in accordance with IS87S(Part 2), IS87S
(Part 3) and IS 875 (Part 4)respectively.
19.4EarthquakeForces
Theearthquakeforces shallbecalculatedIn
accordance with IS 1893.
19.5Shrlnkap,enepandTemperatureElfeets
If the effects of shrinkagc,creepandtemperatureare
liabletoaffectmateriallythesafetyandserviceability
of thestructure.these shallbetakenintoaccountin
thecalculations(see6.2.4,6.Z.5and6.2.6)and
IS875(Part5).
19.5.1Inordinarybuildinp,such•lowrisedwellinp
whoselateraldimensiondo Dotexceed45m, the
32
SECTION3GENERALDESIGNCONSIDERATION
18 BASESFORDESIGN
18.1 AimofDesigD
The aim of design is the achievementof an acceptable
probabilitythatstructuresbeingdesignedwillperform
satisfactorilyduringtheir
intendedlife. Withan
appropriate degree of safety, they should sustain all
the loadsand deformationsof
normalconstructionand
use and haveadequatedurabilityandadequate
resistance to the effects of misuse and fire.
18.2Methodsof Design
18.2.1Structureand structuralelementsshallnonnally
bedesigned by Limit State Method. Account should
betakenofacceptedtheories,experimentand
experienceandtheneedtodesignfor durability.
Calculationsalonedo notproducesafe,serviceableand
durable structures. Suitablematerials,qualitycontrol.
adequate detailing and good supervision are equally
important.
18.2.2Where the Limit State Method can not be
conveniently adopted, Working Stress Method(see
Annex B) may be used.
18.2.3DesignBasedonExperimentalBasis
Designsbasedonexperimentalinvestigationson
modelsorfullsizestructureorelementmay be
accepted if they satisfy the primary requirements
of
18.1and subject to experimental details and the
analysis connected therewith being approved
bythe
engineer-in-charge.
18.2.3.1 Where
.the
designis based on experimental
investigationonfullsizestructureorelement,loadtests
shall
be
carriedout to ensure thefollowing:
a) Thestructureshall satisfy the requirementsfor
deflection
(see
23.2)and cracking(see35.3.2)
when subjected to a load for 24 hequalto the
characteristicload multiplied
by ).33Yr'where"(rshallbetakenfromTable 18,forthelimitstate
ofserviceability.If within 24 h of theremoval
of the load, thestructuredoes
not showa
recovery of at least
7Spercentofthemaximum
deflectionshownduringthe24hunder.theload,
the test loading should
berepeated after a lapse
of 72
h.Therecoveryafterthesecond
testshould
beat least7Spercentof themaximumdeflection
shown during thesecondtest.
NOTE-Ifthemaximumdeflectionin mm, shown duriftl
24hunderloadislessthan401
2/D
whereIistheeffectivespan
in m;andDistheoveralldepthofthesectioninrom,iti.not
necessaryforthe~tobemeasured.
b) Thestructureshall have adequatestrenathto
sustainfor24 h,atotalloadequaltothecharac
teristic load multipliedby1.331,whereY,shall
betakenfrom Table 18 forthelimit state of
collapse.
18.3 DurabWty,WorkmanshipaDd~terlall
It is assumed that the quality of concrete, steel and
other materials and of theworkmanship,as verified
byinspections,
isadequatefotsafety.serviceability
anddurability.
18.4
DesllDProcess
Design.includingdesignfordurability,construction
and use in service shouldbeconsideredas awhole.
Therealizationofdesignobjectivesrequires
compliance
with
clearlydefinedstandardsfor
materials,production,workmanship andalso
maintenance
anduse ofstructureinservice.
19LOADS
AND'ORCES
19.1General
Instructuraldesign,accountshallbetakenofthedead.
imposedandwind loads andforces suchasthose
causedbyearthquake.andeffectsduetoshrinkage,
creep,temperature,etc,whereapplicable.
19.2DeadLoads
Dead loads shallbecalculatedon the basis of unit
weightswhichshallbeestablished
takina into
considerationthe materialsspecifiedfor construction.
19.2.1Alternatively,thedead loadsmaybecalculated
onthebasis of unit weights of materialslivenin
IS875(Part 1).Unlessmoreaccuratecalculationsare
warranted, the unit weightsofplainconcrete and
reinforced concrete made with sand and gravel or
crushed natural stone aggregate
maybetakenas
24
kN/m:\and25kN/m
3
respectively.
19.3ImposedLoads,WIndLoadsand SnowLoIds
Imposed loads. wind loads and snow loads shallbe
assumed in accordance with IS87S(Part 2), IS87S
(Part 3) and IS 875 (Part 4)respectively.
19.4EarthquakeForces
Theearthquakeforces shallbecalculatedIn
accordance with IS 1893.
19.5Shrlnkap,enepandTemperatureElfeets
If the effects of shrinkagc,creepandtemperatureare
liabletoaffectmateriallythesafetyandserviceability
of thestructure.these shallbetakenintoaccountin
thecalculations(see6.2.4,6.Z.5and6.2.6)and
IS875(Part5).
19.5.1Inordinarybuildinp,such•lowrisedwellinp
whoselateraldimensiondo Dotexceed45m, the
32
effects due to temperature fluctuations and shrinkage
and creep can be ignored in design calculations.
19.6Other
ForcesandEffects
In addition, account shall be taken of thefollowing
forces and effects if they are liable to affectmaterially
the safety and serviceability of the structure:
a) Foundation movement
(seeIS 1904),
b) Elastic axial shortening,
c) Soil and fluid pressures
[seeIS 875 (Part5)],
d)Vibration,
e) Fatigue.
oImpact[seeIS 875 (Part 5)],
g)Erection loads(seeIS 875 (Part 2)],and
h) Stressconcentrationeffectdue to point loadand
the like.
19.7CombinationofLoads
The combination of loads shall be as given in IS 875
(Part
S).
19.8 Dead LoadCounteracting OtherLoadsand
Fon:es
When dead load counteracts the effects due to other
loads and forces
instructural memberorjoint, special
care shall be exercised by the designer to ensure
adequate safety for possible
stressreversal.
19.9Deslgn Load
Design loadistheload to betakenfor use in the
appropriate method of design;itis thecharacteristic
loadincaseof
workingstressmethodandcharacteristic
load with appropriate partial safety factors for limit
state design.
20STABILITYOFTHESTRlJCTlJRE
ZO.1Overturnina
Thestabilityofastructureas a wholeagainst
overturning shall be ensured
so that therestoring
moment shan be not less than the sum of 1.2timesthe
maximumoverturningmomentdue
tothecharacteristic
dead load and 1.4 times the maximumoverturning
moment due to the characteristic imposed loads. In
cases where dead load providesthe restoring
moment,
only 0.9times the characteristic dead load shall be
considered. Restoring moment due to imposed
loads
shall be ignored.
20.1.1The anchorages or counterweights provided
foroverhangingmembers(during construction and
service)shouldbesuch thatstaticequilibrium
should remain, even when overturning moment is
doubled.
2116el5/07---6 33
IS456:2000
20.2Sliding
Thestructureshall have a factor against sliding of not
lessthan 1.4underthe most
adversecombinationof the
appliedcharacteristicforces.In thiscaseonly0.9 times
thecharacteristicdead loadshall be takenintoaccount.
20.3ProbableVariationin DeadLoad
Toensure stability at all times, account shall be taken
of
probablevariationsindead loadduringconstruction,
repairor othertemporarymeasures.
Windandseismic
loading shall be treatedasimposed
loading.
20.4MomentConnection
In designing the framework of a buildingprovisions
shall be madebyadequatemoment connectionsorby
itsystem of bracings to effectively transmit all the
horizontalforces tothefoundations.
20.5Lateral Sway
LIndertransient wind loadthelateral sway at the top
should notexceedHI500,where11is thetotalheight
of thebuilding,For seismic loading,referenceshould
he made to IS
J893.
21FIRERESISTANCE
21.1 AstructureOfstructuralelementrequiredto have
fireresistanceshould bedesignedto possess an
appropriatedegreeof resistanceto flamepenetration;
heattransmissionandfailure.Thefireresistanceof a
structuralclementis expressedinterms of time in hours
inaccordancewithIS 1641.Fireresistance of concrete
elements depends
upon details of member size. cover
to
steelreinforcement detailing andtypeofaggregate
(normalweightor light weight) used in concrete.
General requirements for fire protection are given in
IS 1642.
21.2Minimum requirementsof
concretecoverand
memberdimensionsfornormal-weightaggregate
concretemembers soitsto have the requiredfire
resistanceshall be inaccordancewith26.4.3 and
Fig.lrespectively.
21.3 Thereinforcement
detailingshould
reflectthe
changing
patternof the structural section and
ensure
that both .individual clementsandthestructureasa
whole containadequatesupport. tics,bondsand
anchoragesfor
therequired tire resistance..
21.3.1 Additionalmeasuressuch as
applicationof fire
resistant finishes. provision of fireresistant
falseceilingsandsacrificialsteel in tensile zone, shouldhe
adopted incasethe nominal cover required exceeds
40 mm for beams and35mmforslabs,togive
protectionagainst spelling.
21.4Specialistliterature maybereferredto for
determiningfireresistanceof thestructureswhichhave
not been covered in Fig. 1 or Table 16A.
and creep can be ignored in design calculations.
19.6Other
ForcesandEffects
In addition, account shall be taken of thefollowing
forces and effects if they are liable to affectmaterially
the safety and serviceability of the structure:
a) Foundation movement
(seeIS 1904),
b) Elastic axial shortening,
c) Soil and fluid pressures
[seeIS 875 (Part5)],
d)Vibration,
e) Fatigue.
oImpact[seeIS 875 (Part 5)],
g)Erection loads(seeIS 875 (Part 2)],and
h) Stressconcentrationeffectdue to point loadand
the like.
19.7CombinationofLoads
The combination of loads shall be as given in IS 875
(Part
S).
19.8 Dead LoadCounteracting OtherLoadsand
Fon:es
When dead load counteracts the effects due to other
loads and forces
instructural memberorjoint, special
care shall be exercised by the designer to ensure
adequate safety for possible
stressreversal.
19.9Deslgn Load
Design loadistheload to betakenfor use in the
appropriate method of design;itis thecharacteristic
loadincaseof
workingstressmethodandcharacteristic
load with appropriate partial safety factors for limit
state design.
20STABILITYOFTHESTRlJCTlJRE
ZO.1Overturnina
Thestabilityofastructureas a wholeagainst
overturning shall be ensured
so that therestoring
moment shan be not less than the sum of 1.2timesthe
maximumoverturningmomentdue
tothecharacteristic
dead load and 1.4 times the maximumoverturning
moment due to the characteristic imposed loads. In
cases where dead load providesthe restoring
moment,
only 0.9times the characteristic dead load shall be
considered. Restoring moment due to imposed
loads
shall be ignored.
20.1.1The anchorages or counterweights provided
foroverhangingmembers(during construction and
service)shouldbesuch thatstaticequilibrium
should remain, even when overturning moment is
doubled.
2116el5/07---6 33
IS456:2000
20.2Sliding
Thestructureshall have a factor against sliding of not
lessthan 1.4underthe most
adversecombinationof the
appliedcharacteristicforces.In thiscaseonly0.9 times
thecharacteristicdead loadshall be takenintoaccount.
20.3ProbableVariationin DeadLoad
Toensure stability at all times, account shall be taken
of
probablevariationsindead loadduringconstruction,
repairor othertemporarymeasures.
Windandseismic
loading shall be treatedasimposed
loading.
20.4MomentConnection
In designing the framework of a buildingprovisions
shall be madebyadequatemoment connectionsorby
itsystem of bracings to effectively transmit all the
horizontalforces tothefoundations.
20.5Lateral Sway
LIndertransient wind loadthelateral sway at the top
should notexceedHI500,where11is thetotalheight
of thebuilding,For seismic loading,referenceshould
he made to IS
J893.
21FIRERESISTANCE
21.1 AstructureOfstructuralelementrequiredto have
fireresistanceshould bedesignedto possess an
appropriatedegreeof resistanceto flamepenetration;
heattransmissionandfailure.Thefireresistanceof a
structuralclementis expressedinterms of time in hours
inaccordancewithIS 1641.Fireresistance of concrete
elements depends
upon details of member size. cover
to
steelreinforcement detailing andtypeofaggregate
(normalweightor light weight) used in concrete.
General requirements for fire protection are given in
IS 1642.
21.2Minimum requirementsof
concretecoverand
memberdimensionsfornormal-weightaggregate
concretemembers soitsto have the requiredfire
resistanceshall be inaccordancewith26.4.3 and
Fig.lrespectively.
21.3 Thereinforcement
detailingshould
reflectthe
changing
patternof the structural section and
ensure
that both .individual clementsandthestructureasa
whole containadequatesupport. tics,bondsand
anchoragesfor
therequired tire resistance..
21.3.1 Additionalmeasuressuch as
applicationof fire
resistant finishes. provision of fireresistant
falseceilingsandsacrificialsteel in tensile zone, shouldhe
adopted incasethe nominal cover required exceeds
40 mm for beams and35mmforslabs,togive
protectionagainst spelling.
21.4Specialistliterature maybereferredto for
determiningfireresistanceof thestructureswhichhave
not been covered in Fig. 1 or Table 16A.
IS456:2000
BEAMS
SOLID SLAB -Pw~·
RIBIWAFFEL SLAB
SLABS
~
::b
".."..
~f.t':
ONE FACE EXPOSE
-IbJ...
FULL VEXPOSED
COLUMNS
--_....._.__....... ------_._--
ColumnDimensiontbfirDJ MinimumWallThicknt.u
FireMilJimum Rib Minimum ...-
......-
....
Resis-/team WidthThicknessFully 50% One 1'<0.4% 04%sp.sl% 1'>1%
tllme Width /11SlabsofFloorsExposed EXPOliCd Face
"
b b
w
D Bxposed
mm mill mID IIIID 111m mm mm mm mm
0.5 200 125 75 150 m tOO 150 100 100
I 200125 95 200 160 120 ISO 120 100
1.5 200 12S 110 250 2(X) 140 175 140 100
2 ZOO 125 125 ~on200 160 160 100
3 240 ISO 150 400 .100 200 200 150
4 280175 170 450 350 240 240 180
NOTES
1Theseminimumdimensionsrelatespecificallyto thecoversgivenin Teble16A.
:zpisthepercentageof steelreinforcement.
FlO. 1MINIMUMDIMENSIONS OF REINFURCEDCONCRE'1llMEMBERSFORFIRERESiSTANCE
22ANALYSIS
22.1General
Allstructuresmay beanalyzed bythelinear
clastictheorytocalculateinternalactions
producedbydesignloads.In lieu ofrigorouselastic
analysis, a simplified analysisasgiven in 22.4 for
framesandasgivenin22.5forcontinuousbeamsmay
beadopted.
22.2EffectiveSpan
Unlessotherwisespecified,the effective span of a
membershallbeasfollows:
a}Simply Supported Beam orSlab-Theeffective
spanofamemberthatis notbuiltintegrally with
itssupportsshallbetakenasclearspanplusthe
effectivedepthofslaborbeamorcentretocentre
ofsupports.whicheveris less.
34
BEAMS
SOLID SLAB -Pw~·
RIBIWAFFEL SLAB
SLABS
~
::b
".."..
~f.t':
ONE FACE EXPOSE
-IbJ...
FULL VEXPOSED
COLUMNS
--_....._.__....... ------_._--
ColumnDimensiontbfirDJ MinimumWallThicknt.u
FireMilJimum Rib Minimum ...-
......-
....
Resis-/team WidthThicknessFully 50% One 1'<0.4% 04%sp.sl% 1'>1%
tllme Width /11SlabsofFloorsExposed EXPOliCd Face
"
b b
w
D Bxposed
mm mill mID IIIID 111m mm mm mm mm
0.5 200 125 75 150 m tOO 150 100 100
I 200125 95 200 160 120 ISO 120 100
1.5 200 12S 110 250 2(X) 140 175 140 100
2 ZOO 125 125 ~on200 160 160 100
3 240 ISO 150 400 .100 200 200 150
4 280175 170 450 350 240 240 180
NOTES
1Theseminimumdimensionsrelatespecificallyto thecoversgivenin Teble16A.
:zpisthepercentageof steelreinforcement.
FlO. 1MINIMUMDIMENSIONS OF REINFURCEDCONCRE'1llMEMBERSFORFIRERESiSTANCE
22ANALYSIS
22.1General
Allstructuresmay beanalyzed bythelinear
clastictheorytocalculateinternalactions
producedbydesignloads.In lieu ofrigorouselastic
analysis, a simplified analysisasgiven in 22.4 for
framesandasgivenin22.5forcontinuousbeamsmay
beadopted.
22.2EffectiveSpan
Unlessotherwisespecified,the effective span of a
membershallbeasfollows:
a}Simply Supported Beam orSlab-Theeffective
spanofamemberthatis notbuiltintegrally with
itssupportsshallbetakenasclearspanplusthe
effectivedepthofslaborbeamorcentretocentre
ofsupports.whicheveris less.
34
b)Continuous Beam or Slab- In the case of
continuousbeam or slab.jfthewidthofthe
support is less than
1/12ofthe clearspan, the
effectivespan shall be as in 22.2
(a).Ifthe
supports are wider than 1/12 of the clearspan
or 600 mm whichever is less, the effective span
shall be taken as under:
1) For end span with one end fixed and the
other continuous or for intermediate spans.
the effective span shall be the clear span
between
supports;
2) For end span with one end free and theother
continuous, the effective span shall be equal
to the clear
spanplus half the effectivedepth
of the beam or slab or the clear span
plus
half the width of the discontinuous support,
whichever is less;
3) In the case of spans with roller or rocket
bearings. the effective span shall
alwayshe
the distance betweenthe centres ofbearings.
c)
Cantilever-The effectivelengthof a cantilever
shall
hetakenasits length to thefaceof the
support plushalftheeffectivedepthexcept
whereitforms theendofa continuous beam
where the length to thecentreof support shall
be taken.
d)
Frames-In the analysisof
acontinuous Irarne,
centre tocentredistanceshallheused.
22.3 Stiffness
22.3.1RelativeStiffness
The relative stiffness of the membersmaybe based on
the
momentof inertiaofthe section determined
on
the basis ofanyoneofthefollowingdefinitions:
a)Grosssection- Thecross-sectionofthe
memberignoringreinforcement:
b)Transformed section- 'Theconcretecross
sectionplustheareaofrcintorccmcrn
transformed on thebasisof modularratio(St'l'
B-I.3);or
c)Crackedsection_.-The area ofconcretein
compressionplus the area of
reinforcement
transformed on the basis of modular
rutin.
The assumptions madeshallbe consistent for(111the
membersof thestructurethroughoutanyanalysis.
22.3.2For deflectioncalculations,appropriate values
of moment of inertia as specified in Annex CshGUIU
be used.
22.4StructuralFrames
The simplifying assumptions as given in 22.4.1
to22..4.3maybe used in the analysis of frames.
35
IS456:2000
22.4.1Arrangementoflmposed Load
a) Considerationmaybe limited to combinations
of:
1) Design dead load on all spans with full
designimposedload on two adjacent spans;
and
2)Design dead load onallspans with full
design imposed loadonalternate spans.
b) When design imposed load does not exceed
three-fourths of the design dead toad, the load
arrangement
maybe designdead loadand design
imposed load on all
thespans.
NOTE----.For beams andslabscontinuousoversupport
22.4.1Ca)rna)'beassumed,
22.4.2 Substitute Frame
For determining the moments andshearsatanyfloor
or roof level due to
gravity loads, the beams atthat
level together with columns
aboveandbelow withtheir
farendsIixedmay be considered to constitute the
frame.
22.4.2.1Wheresideswayconsideration becomes
criticaldueto unsymmctry in geometryorloading,
rigorousanalysisITIayberequired.
22.4.3 For lateral loads, simplified methods
maybe
usedtoobtain themoments andshearsfor structures
that
arcsvmmetrical. For unsymmetrical or very tall
structures. more rigorous methods should be used.
22.5Moment andShear
Coefficientfifor
ContinuousBeams
22.5.1 Unless more exactestimatesare made. for
beamsofuniformcross-sectionwhichsupport
substantially
uniformlydistributedloadsover three orIlHire:'\1',UlSwhichdonotdifferbymore-than15percent
ofthelongest,the bending moments andshearforces
usedindesignmaybe obtained using the coefficients
giveninTable1.2andTable13 respectively.
For
momentsat
supportswhere two unequal spans
meet orjn casewherethespansarenotequallyloaded,
theaverage ofttlctwo values for the negative moment
attheStlpptutmayhetaken for design.
Where coeflicients given in Table 12 are used for
calculationofbendingmoments,redistributionreferred
toin22.7shallnotbepermitted.
22.5.2 Beamsand Slabs Over FreeEnd Supports
Where a member is built into amasonrywall which
develops nnly partial restraint. the member shallbe
designedto resist a negative moment att.heface of the
supportofW1/24whereWis the total design load
and
lis the effective span, or such other restraining
moment as may be shown to
heapplicable,Forsuch a
condition shear coefficient given in Table 13 at the
end support may be increasedhy0.05.
continuousbeam or slab.jfthewidthofthe
support is less than
1/12ofthe clearspan, the
effectivespan shall be as in 22.2
(a).Ifthe
supports are wider than 1/12 of the clearspan
or 600 mm whichever is less, the effective span
shall be taken as under:
1) For end span with one end fixed and the
other continuous or for intermediate spans.
the effective span shall be the clear span
between
supports;
2) For end span with one end free and theother
continuous, the effective span shall be equal
to the clear
spanplus half the effectivedepth
of the beam or slab or the clear span
plus
half the width of the discontinuous support,
whichever is less;
3) In the case of spans with roller or rocket
bearings. the effective span shall
alwayshe
the distance betweenthe centres ofbearings.
c)
Cantilever-The effectivelengthof a cantilever
shall
hetakenasits length to thefaceof the
support plushalftheeffectivedepthexcept
whereitforms theendofa continuous beam
where the length to thecentreof support shall
be taken.
d)
Frames-In the analysisof
acontinuous Irarne,
centre tocentredistanceshallheused.
22.3 Stiffness
22.3.1RelativeStiffness
The relative stiffness of the membersmaybe based on
the
momentof inertiaofthe section determined
on
the basis ofanyoneofthefollowingdefinitions:
a)Grosssection- Thecross-sectionofthe
memberignoringreinforcement:
b)Transformed section- 'Theconcretecross
sectionplustheareaofrcintorccmcrn
transformed on thebasisof modularratio(St'l'
B-I.3);or
c)Crackedsection_.-The area ofconcretein
compressionplus the area of
reinforcement
transformed on the basis of modular
rutin.
The assumptions madeshallbe consistent for(111the
membersof thestructurethroughoutanyanalysis.
22.3.2For deflectioncalculations,appropriate values
of moment of inertia as specified in Annex CshGUIU
be used.
22.4StructuralFrames
The simplifying assumptions as given in 22.4.1
to22..4.3maybe used in the analysis of frames.
35
IS456:2000
22.4.1Arrangementoflmposed Load
a) Considerationmaybe limited to combinations
of:
1) Design dead load on all spans with full
designimposedload on two adjacent spans;
and
2)Design dead load onallspans with full
design imposed loadonalternate spans.
b) When design imposed load does not exceed
three-fourths of the design dead toad, the load
arrangement
maybe designdead loadand design
imposed load on all
thespans.
NOTE----.For beams andslabscontinuousoversupport
22.4.1Ca)rna)'beassumed,
22.4.2 Substitute Frame
For determining the moments andshearsatanyfloor
or roof level due to
gravity loads, the beams atthat
level together with columns
aboveandbelow withtheir
farendsIixedmay be considered to constitute the
frame.
22.4.2.1Wheresideswayconsideration becomes
criticaldueto unsymmctry in geometryorloading,
rigorousanalysisITIayberequired.
22.4.3 For lateral loads, simplified methods
maybe
usedtoobtain themoments andshearsfor structures
that
arcsvmmetrical. For unsymmetrical or very tall
structures. more rigorous methods should be used.
22.5Moment andShear
Coefficientfifor
ContinuousBeams
22.5.1 Unless more exactestimatesare made. for
beamsofuniformcross-sectionwhichsupport
substantially
uniformlydistributedloadsover three orIlHire:'\1',UlSwhichdonotdifferbymore-than15percent
ofthelongest,the bending moments andshearforces
usedindesignmaybe obtained using the coefficients
giveninTable1.2andTable13 respectively.
For
momentsat
supportswhere two unequal spans
meet orjn casewherethespansarenotequallyloaded,
theaverage ofttlctwo values for the negative moment
attheStlpptutmayhetaken for design.
Where coeflicients given in Table 12 are used for
calculationofbendingmoments,redistributionreferred
toin22.7shallnotbepermitted.
22.5.2 Beamsand Slabs Over FreeEnd Supports
Where a member is built into amasonrywall which
develops nnly partial restraint. the member shallbe
designedto resist a negative moment att.heface of the
supportofW1/24whereWis the total design load
and
lis the effective span, or such other restraining
moment as may be shown to
heapplicable,Forsuch a
condition shear coefficient given in Table 13 at the
end support may be increasedhy0.05.
IS456: 2000
Table11Bending Moment Coefficients
(Clause22.5.1)
Type of Load SpanMoments SupportMoments
..
"."
; , t"t ,
Near Middle At Middle At Support AtOther
of EndSpan of Interior Next tothe Interior
Span End Support Supports
(1) (2) (:l) (4) (5)
Deadloadnodimposed 1 I I I
+- +-
load (fixed) 12 16 10 12
I
+
12
1
+-
10
1 1
9 9
NOTE- For obtainingthe bendingmoment,thecoefficientshallbemultipliedbythe total designloadandeffectivespan.
Imposedload (not
fixed)
Table 13Shearfor Coefficients
iClauses22.5.1and22.5.2)
AtAllOther
InteriorSupports
AtSupportNext to the
EndSupport
t"t
&;terSide InnerSide
At End
Support
Type
01Load
(~)
0.5
0.6
0.6
(4)
0.55
(3)
0.6
0.6
(2)
0.4
0.45
(I)
Deadloudandimposed
load(fixed)
Imposedload(not
fixed)
NOTE- For obtainingthe shear force.the coefficientshallbemultipliedbythetotaldesignload.
22.6CriticalSections forMoment andShear
22.6.1Formonolithic construction,themoments
computedat the face of thesupportsshall be usedin
thedesign ofthemembersat thosesections.
Fornon..
monolithicconstructionthedesignof themembershall
be done keeping in view 22.2.
22.6.2Critical Section/orShear
The shearscomputedat the face of the supportshall
beused in the design of the member at that section
except
asin22.6.2.1.
22.6.Z.1When the reaction in the direction of the
applied shear introduces compression
intothe end
region of the member, sections located at a distance
Jessthandfrom the face of the supportmaybe
designed for the same shear as that computed atdistanced(seeFig. 2).
N()TE-The aboveclausesare applicablefor beamsgenerally
carryinguniformlydistributedloudor wheretheprincipalload
islocatedfurtherthan"2d(ruinthefaceof the support.
22.7RedistributionofMoments
Redistributionof momentsmaybedoneinaccordance
with37.1.1 for limit state methodand inaccordance
with8-1.2forworkingstressmethod.However,where
simplifiedanalysisusing coefficients is adopted,
redistributionof
momentsshall notbedone.
23BEAMS
23.0 Effective Depth
Effectivedepth of a beam
isthedistancebetweenthe
centroid of the area oftensionreinforcementand the
maximumcompressionfibre,excludingthethickness
offinishingmaterial not placedmonolithically with
thememberandthethicknessofanyconcreteprovided
to allow forwear.Thiswillnotapplyto deep beams.
23.1 T-Beams and L·Beams
23.1.1General
A slab which is assumed to act as a compression
flange of a T-beam
orL-beam shallsatisfythe
following:
a) The slab shallbecastintegrallywiththe web,
or the web and the slab shall be effectively
bondedtogetherin anyothermanner;and
b) If the mainreinforcementofthe slabisparallel
to the beam,transversereinforcementshallbe
providedas in Fig. 3; suchreinforcementshall
not be lessthan60percentofthemain
reinforcementat mid span of the slab.
23.1.2Effective WidthofFlang,
In theabsenceof moreaccuratedetermination.the
effectivewidthof
flangemaybetakenasthefollowing
36
Table11Bending Moment Coefficients
(Clause22.5.1)
Type of Load SpanMoments SupportMoments
..
"."
; , t"t ,
Near Middle At Middle At Support AtOther
of EndSpan of Interior Next tothe Interior
Span End Support Supports
(1) (2) (:l) (4) (5)
Deadloadnodimposed 1 I I I
+- +-
load (fixed) 12 16 10 12
I
+
12
1
+-
10
1 1
9 9
NOTE- For obtainingthe bendingmoment,thecoefficientshallbemultipliedbythe total designloadandeffectivespan.
Imposedload (not
fixed)
Table 13Shearfor Coefficients
iClauses22.5.1and22.5.2)
AtAllOther
InteriorSupports
AtSupportNext to the
EndSupport
t"t
&;terSide InnerSide
At End
Support
Type
01Load
(~)
0.5
0.6
0.6
(4)
0.55
(3)
0.6
0.6
(2)
0.4
0.45
(I)
Deadloudandimposed
load(fixed)
Imposedload(not
fixed)
NOTE- For obtainingthe shear force.the coefficientshallbemultipliedbythetotaldesignload.
22.6CriticalSections forMoment andShear
22.6.1Formonolithic construction,themoments
computedat the face of thesupportsshall be usedin
thedesign ofthemembersat thosesections.
Fornon..
monolithicconstructionthedesignof themembershall
be done keeping in view 22.2.
22.6.2Critical Section/orShear
The shearscomputedat the face of the supportshall
beused in the design of the member at that section
except
asin22.6.2.1.
22.6.Z.1When the reaction in the direction of the
applied shear introduces compression
intothe end
region of the member, sections located at a distance
Jessthandfrom the face of the supportmaybe
designed for the same shear as that computed atdistanced(seeFig. 2).
N()TE-The aboveclausesare applicablefor beamsgenerally
carryinguniformlydistributedloudor wheretheprincipalload
islocatedfurtherthan"2d(ruinthefaceof the support.
22.7RedistributionofMoments
Redistributionof momentsmaybedoneinaccordance
with37.1.1 for limit state methodand inaccordance
with8-1.2forworkingstressmethod.However,where
simplifiedanalysisusing coefficients is adopted,
redistributionof
momentsshall notbedone.
23BEAMS
23.0 Effective Depth
Effectivedepth of a beam
isthedistancebetweenthe
centroid of the area oftensionreinforcementand the
maximumcompressionfibre,excludingthethickness
offinishingmaterial not placedmonolithically with
thememberandthethicknessofanyconcreteprovided
to allow forwear.Thiswillnotapplyto deep beams.
23.1 T-Beams and L·Beams
23.1.1General
A slab which is assumed to act as a compression
flange of a T-beam
orL-beam shallsatisfythe
following:
a) The slab shallbecastintegrallywiththe web,
or the web and the slab shall be effectively
bondedtogetherin anyothermanner;and
b) If the mainreinforcementofthe slabisparallel
to the beam,transversereinforcementshallbe
providedas in Fig. 3; suchreinforcementshall
not be lessthan60percentofthemain
reinforcementat mid span of the slab.
23.1.2Effective WidthofFlang,
In theabsenceof moreaccuratedetermination.the
effectivewidthof
flangemaybetakenasthefollowing
36
IS 456: 2000
t
(0) (b)
d
FIG.2TYPICALSUPPORTCONOmONSFORLOCATINGFACI'OREDSHEARFORCE
but in no case greater than the breadthof the webplus
halfthesumofthecleardistancestothe adjacentbeams
on either side.
a)ForT-beams,h,=~+b",+6D,
I
b) For L-beams,b,=~+b
w
+3D,
12
c)For isolated beams, the effective flange width
shallbeobtainedas belowbutinnocasegreater
than the actual
width:
T-beam,b,
.~I)o +b..
.:JL+4
b
Lbb
·
O.S
Inb
-eam,'=~+ w
...!l.+4
b
where
b,=effective widthofflange,
In=distance betweenpointsof zeromoments
in the beam,
b",=breadthof the web,
Dr=thicknessof flange, and
b=actual width of theflange.
NOTE- Porcontinuousbeamsandframe.,",,'maybe
assumedlUI0.7time.theeffectivespan.
23.2Controlof Defledlon
The deflection of • structureor part thereofshall not
adverselyaffecttheappearanceorefficiencyof the
structureorfinishesorpartitions.Thedeflectionshall
generallybe limitedto thefollowing:
a) The final deflectiondue to all loadsincluding
the effectsoftemperature,creep andshrinkage
and measured from the as-cast level of the
supportsof
floors,roofsand allotherhorizontal
members,shouldnotnormally
exceedspanl2S0.
b) Thedeflectionincludingtheeffectsof
temperature,creepandshrinkageoccurringafter
erection of partitions and the application of
finishesshould not normally exceed span/3S0
or 20 mmwhicheveris less.
23.2.1The verticaldeflectionlimits
may.generallybe
assumedtobe satisfiedprovidedthatthespantodepth
ratios
arenotgreaterthanthevaluesobtainedas below:
a)
Basicvalues of span to effective depth ratios
for spans up to 10m:
Cantilever 7
Simplysupported 20
Continuous 26
b) Forspansabove 10m,the valuesin (a) may be
multiplied by 10/span in metres, except for
cantileverin whichcasedeflectioncalculations
shouldbe made.
c)Dependingon the area and thestress
of
steelfor tensionreinforcement,the valuesin(a)
or (b) shallbemodifiedbymultiplyingwiththe
modificationfactor obtainedas per Fig. 4.
d)Dependingon theareaofcompression
reinforcement,the value of span to depth ratio
befurther modified by multiplying with the
modificationfactorobtainedas per Fig.S.
37
t
(0) (b)
d
FIG.2TYPICALSUPPORTCONOmONSFORLOCATINGFACI'OREDSHEARFORCE
but in no case greater than the breadthof the webplus
halfthesumofthecleardistancestothe adjacentbeams
on either side.
a)ForT-beams,h,=~+b",+6D,
I
b) For L-beams,b,=~+b
w
+3D,
12
c)For isolated beams, the effective flange width
shallbeobtainedas belowbutinnocasegreater
than the actual
width:
T-beam,b,
.~I)o +b..
.:JL+4
b
Lbb
·
O.S
Inb
-eam,'=~+ w
...!l.+4
b
where
b,=effective widthofflange,
In=distance betweenpointsof zeromoments
in the beam,
b",=breadthof the web,
Dr=thicknessof flange, and
b=actual width of theflange.
NOTE- Porcontinuousbeamsandframe.,",,'maybe
assumedlUI0.7time.theeffectivespan.
23.2Controlof Defledlon
The deflection of • structureor part thereofshall not
adverselyaffecttheappearanceorefficiencyof the
structureorfinishesorpartitions.Thedeflectionshall
generallybe limitedto thefollowing:
a) The final deflectiondue to all loadsincluding
the effectsoftemperature,creep andshrinkage
and measured from the as-cast level of the
supportsof
floors,roofsand allotherhorizontal
members,shouldnotnormally
exceedspanl2S0.
b) Thedeflectionincludingtheeffectsof
temperature,creepandshrinkageoccurringafter
erection of partitions and the application of
finishesshould not normally exceed span/3S0
or 20 mmwhicheveris less.
23.2.1The verticaldeflectionlimits
may.generallybe
assumedtobe satisfiedprovidedthatthespantodepth
ratios
arenotgreaterthanthevaluesobtainedas below:
a)
Basicvalues of span to effective depth ratios
for spans up to 10m:
Cantilever 7
Simplysupported 20
Continuous 26
b) Forspansabove 10m,the valuesin (a) may be
multiplied by 10/span in metres, except for
cantileverin whichcasedeflectioncalculations
shouldbe made.
c)Dependingon the area and thestress
of
steelfor tensionreinforcement,the valuesin(a)
or (b) shallbemodifiedbymultiplyingwiththe
modificationfactor obtainedas per Fig. 4.
d)Dependingon theareaofcompression
reinforcement,the value of span to depth ratio
befurther modified by multiplying with the
modificationfactorobtainedas per Fig.S.
37
BEAM
IS456:2000
I I
II
II
T-+----+-+----+---
Xl II
t--~-
SECTIONXX
FIG.3TRANSVERSEREINFORCEMENTINFLANGBOFT-BEAMWHEN MAINREINFORCEMENTOf
SLABISPARAIJ.ELTOTHEBEAM
e) Forflangedbeams, the values of (a) or (b) be
modified
asper Fig. 6 and the reinforcement
percentageforuseinFig.4and
5shouldbebased
on
areaofsectionequaltob,d.
NOTE-Whendeflectionsarerequiredtobecalculated,the
methodgiveninAnnexCmaybeused.
2·0
',6
\\ \\ \
\'
\
"
r-,
\\-,r-,
I<,
r-,
\
<,
........
r----
-..
~~ I'-...~
r-....
f••'45
-r-,
<, I"'--~ I-...
10.",. r---
f""90
<,r--
I--f--...fu240r---
h·290
,
I
Note:f.ISSTEELSTRESSOFSERVICE
,LOADSINN/mm
2
I "
o 0'4 0,' ',21'6 2·0 2"
PERCENTAGE TENSIONREINFORCEMENT
I..0.58f.ArMofCI'OII'_tionohteelrequired
•.,AreaofCmll•aectionofsteelprovided
Flo.4MODIACATJONFAcroRFORTENSIONREINFORCEMENT
38
2'8)0
IS456:2000
I I
II
II
T-+----+-+----+---
Xl II
t--~-
SECTIONXX
FIG.3TRANSVERSEREINFORCEMENTINFLANGBOFT-BEAMWHEN MAINREINFORCEMENTOf
SLABISPARAIJ.ELTOTHEBEAM
e) Forflangedbeams, the values of (a) or (b) be
modified
asper Fig. 6 and the reinforcement
percentageforuseinFig.4and
5shouldbebased
on
areaofsectionequaltob,d.
NOTE-Whendeflectionsarerequiredtobecalculated,the
methodgiveninAnnexCmaybeused.
2·0
',6
\\ \\ \
\'
\
"
r-,
\\-,r-,
I<,
r-,
\
<,
........
r----
-..
~~ I'-...~
r-....
f••'45
-r-,
<, I"'--~ I-...
10.",. r---
f""90
<,r--
I--f--...fu240r---
h·290
,
I
Note:f.ISSTEELSTRESSOFSERVICE
,LOADSINN/mm
2
I "
o 0'4 0,' ',21'6 2·0 2"
PERCENTAGE TENSIONREINFORCEMENT
I..0.58f.ArMofCI'OII'_tionohteelrequired
•.,AreaofCmll•aectionofsteelprovided
Flo.4MODIACATJONFAcroRFORTENSIONREINFORCEMENT
38
2'8)0
18456:2000
~
100"""
.-.-.~
~
~
~
L/
V
/
V
,/
0-50'-001-50 2-00 2-50
PERCENTAGE COMPRESSION REINFORCEMENT
FIG.5MOOIHCATIONFACTORFOR COMPRESSIONREtNPoRCBMENT
1/
/
/"
/
/
0095
a:
e
~e-sc
&L
z0.85
Q
t
~0·80
a:
1'100
0·75
0.70
o0'20'40·80'81·0
RATIOOFWEBWIDTH
TOFLANGEWIDTH
FIG.6REDUCTIONFACTORSFORRA'110SOF'SPAN TOEJ-rEcnVEDEPTH FORFLANGEDBEAMS
23.3SlendernessLimit'!forBeamstoEnsure
LateralStability
A simply supported or continuous beam shallbeso
proportioned that the clear distance between the lateral
. 250b
z
restraints doesnotexceed60bOf--whichever
d
is less, wheredis theeffectivedepth of the beam and
bthe breadth of the compression face midway betwecn
the lateral restraints.
For a cantilever, the clear distance from the free end
ofthecantileverto the lateral restraint shall not
100b
z
exceed25bor_.- whichever is less.
d
24SOLIDSLABS
24.1General
Theprovisionsof13.2forbeamsapply toslabs
also.
NOTBS
1
Forslabsspanninlintwodirections,theshorterofthetwo
spansshouldbeused for calculating the span toetTective
depthratios.
2Fortwo-wavslabsofshorterspans(up to3.~m) with mild
stoelreinforcement,the span tooveralldepthratiosgiven
belowmaygenerallybe assumed 10satisfyvertical
deflectionlimits for loadingclass up to 3kN/m
J
•
Simplysupported
slabs 3S
Continuousslabs 40
For highstn:ngthdefonned barsofsmdeFe41~.the values
givenaboveshouldbemultipliedby 0.8.
24.2SlabsContinuous OverSupports
Slabs spanning in one direction and continuous over
supports shallbedesigned according to the provisions
applicableto continuous beams.
24.3S~~bsMonolithicwithSupports
Bendingmomentsin slabs(exceptflatslabs)constructed
monolithically with the supports shallbecalculated by
takingsuch slabs eitherascontinuousoversupportsand
39
~
100"""
.-.-.~
~
~
~
L/
V
/
V
,/
0-50'-001-50 2-00 2-50
PERCENTAGE COMPRESSION REINFORCEMENT
FIG.5MOOIHCATIONFACTORFOR COMPRESSIONREtNPoRCBMENT
1/
/
/"
/
/
0095
a:
e
~e-sc
&L
z0.85
Q
t
~0·80
a:
1'100
0·75
0.70
o0'20'40·80'81·0
RATIOOFWEBWIDTH
TOFLANGEWIDTH
FIG.6REDUCTIONFACTORSFORRA'110SOF'SPAN TOEJ-rEcnVEDEPTH FORFLANGEDBEAMS
23.3SlendernessLimit'!forBeamstoEnsure
LateralStability
A simply supported or continuous beam shallbeso
proportioned that the clear distance between the lateral
. 250b
z
restraints doesnotexceed60bOf--whichever
d
is less, wheredis theeffectivedepth of the beam and
bthe breadth of the compression face midway betwecn
the lateral restraints.
For a cantilever, the clear distance from the free end
ofthecantileverto the lateral restraint shall not
100b
z
exceed25bor_.- whichever is less.
d
24SOLIDSLABS
24.1General
Theprovisionsof13.2forbeamsapply toslabs
also.
NOTBS
1
Forslabsspanninlintwodirections,theshorterofthetwo
spansshouldbeused for calculating the span toetTective
depthratios.
2Fortwo-wavslabsofshorterspans(up to3.~m) with mild
stoelreinforcement,the span tooveralldepthratiosgiven
belowmaygenerallybe assumed 10satisfyvertical
deflectionlimits for loadingclass up to 3kN/m
J
•
Simplysupported
slabs 3S
Continuousslabs 40
For highstn:ngthdefonned barsofsmdeFe41~.the values
givenaboveshouldbemultipliedby 0.8.
24.2SlabsContinuous OverSupports
Slabs spanning in one direction and continuous over
supports shallbedesigned according to the provisions
applicableto continuous beams.
24.3S~~bsMonolithicwithSupports
Bendingmomentsin slabs(exceptflatslabs)constructed
monolithically with the supports shallbecalculated by
takingsuch slabs eitherascontinuousoversupportsand
39
d) Forcantilever solidslabs, theeffectivewidth
shall hecalculatedinaccordancewith the
following equation:
b
er=1.2a
l
+a
c) For two or more loads not in a line in the
directionof thespan.iftheeffectivewidthof
slab
foroneloaddoesnotoverlaptheeffective
widthofslabforanotherload,bothcalculated
as in (a)above,thentheslabforeach loadcan
bedesignedseparately.If the effectivewidth
ofslabforoneloadoverlapsthe
effectivewidth
ofslabfor anadjacentload,theoverlapping
portionof theslabshallbedesignedfor the
combinedeffectofthetwoloads.
Table14Values01kforSbnplySupportedand
ContinuousSlabs
(Clause24.3.2.1)
where
ber=effectivewidth,
ill=distanceoftheconcentratedload from the
face of the cantilever support, and
a=widt.hof contact area of the concentrated
load measured parallel to the supporting
edge.
Providedthattheeffectivewidthof thecantilever
slab shall not exceedone-thirdthe length of the
cantileverslab
measuredparallelto
thefixededge.
Andprovidedfurtherthat whentheconcentrated
loadisplacedneartheextremeendsofthelength
of cantilever slab in the direction parallel to the
fixed edge. the effective width shall not exceed
the above value, nor shall it exceed half the
abovevalue
plusthedistanceof theconcentrated
load from theextremeend measured in the
directionparallel to thefixededge. .
24.3.2.2For slabs other than solid slabs, the effective
width shall depend on the ratio of the transverse and
longitudinalflexural rigidities of the slab. Where this
ratiois one,thatis,wherethetransverseand
longitudinal
flexuralrigidities arcapproximately
equal,
thevalue of effective width as found for solid
slabs
maybe-used.But as theratiodecreases,
proportionatelysmaller value shall
hetaken.
IS
456:2000
capableof free rotation.or as membersof a continuous
frameworkwith thesupports,taking into account the
stiffness
of suchsupports.If suchsupportsareformed
due to beamswhichjustify fixityat thesupportof slabs,
then the effects on the supporting beam, such as, the
bending of the web in thetransversedirection of the
hewnandthetorsioninthelongitudinaldirection ofthe
beam. whereverapplicable,shall also beconsideredin
the design of the beam.
24.3.1 For the purpose of calculation of
momentsin
slabs inamonolithic structure,itwillgenerallybe
sufficientlyaccurateto assumethatmembersconnected
to the ends of such slabs are fixed in position and
direction at
theendsremote from their connections
with the slabs.
24.3.1SlabsCarrying ConcentratedLoad
24.3.2.1Ifa solidslabsupportedon twooppositeedges,
carriesconcentratedloads the maximum bending
moment caused
bythe concentrated loads shall be
assumed to be resisted by an effective width of slab
(measuredparallel to the supportingedges)asfollows:
a) For a single concentrated load. the effective
width shall
becalculated in accordancewith the
following equation provided that it shall not
exceedthe actual width of the slab:
ber=kx(1-
..!..)+a
lef
where
b
d=effective width of slab,
k=constanthavingthe valuesgiveninTable
14depending upon the ratio of the width
oftheslab
(/~to the effective spanIe{,
x=distanceof thecentroidofthe
concentrated
loadfromnearersupport,
I
r f=effective span, and
a=widthof the contactareaofthe
concentrated load from nearer support
measured parallel to the supportededge.
And provided further that in case of a load near
the unsupported edge of a slab. the effective
width shall not exceed the above value nor half
theabovevalueplusthedistanceoftheloadfrom
theunsupportededge.
b) For two or more concentrated loads placed in a
line in the direction of
thespan, the bending
momentpermetrewidth of slab shall be
calculated separately for each loadaccordingto
its appropriateeffectivewidthof slab calculated
as in (a) above and added together for design
calculations.
40
0.1
0.2
0.3
0.4
O.S
0.6
0.7
0.8
0.9
1.0
andabove
ilorSlmpl,
SupportedS....
0.4
0.8
1.16
1.48
1.72
1.96
2.12
2.24
2.36
2.48
ilorCoatlDUQUI
51••
0.4
0.8
1.16
1.44
1.68
1.84.
1.96
2.08
2.16
2.24
shall hecalculatedinaccordancewith the
following equation:
b
er=1.2a
l
+a
c) For two or more loads not in a line in the
directionof thespan.iftheeffectivewidthof
slab
foroneloaddoesnotoverlaptheeffective
widthofslabforanotherload,bothcalculated
as in (a)above,thentheslabforeach loadcan
bedesignedseparately.If the effectivewidth
ofslabforoneloadoverlapsthe
effectivewidth
ofslabfor anadjacentload,theoverlapping
portionof theslabshallbedesignedfor the
combinedeffectofthetwoloads.
Table14Values01kforSbnplySupportedand
ContinuousSlabs
(Clause24.3.2.1)
where
ber=effectivewidth,
ill=distanceoftheconcentratedload from the
face of the cantilever support, and
a=widt.hof contact area of the concentrated
load measured parallel to the supporting
edge.
Providedthattheeffectivewidthof thecantilever
slab shall not exceedone-thirdthe length of the
cantileverslab
measuredparallelto
thefixededge.
Andprovidedfurtherthat whentheconcentrated
loadisplacedneartheextremeendsofthelength
of cantilever slab in the direction parallel to the
fixed edge. the effective width shall not exceed
the above value, nor shall it exceed half the
abovevalue
plusthedistanceof theconcentrated
load from theextremeend measured in the
directionparallel to thefixededge. .
24.3.2.2For slabs other than solid slabs, the effective
width shall depend on the ratio of the transverse and
longitudinalflexural rigidities of the slab. Where this
ratiois one,thatis,wherethetransverseand
longitudinal
flexuralrigidities arcapproximately
equal,
thevalue of effective width as found for solid
slabs
maybe-used.But as theratiodecreases,
proportionatelysmaller value shall
hetaken.
IS
456:2000
capableof free rotation.or as membersof a continuous
frameworkwith thesupports,taking into account the
stiffness
of suchsupports.If suchsupportsareformed
due to beamswhichjustify fixityat thesupportof slabs,
then the effects on the supporting beam, such as, the
bending of the web in thetransversedirection of the
hewnandthetorsioninthelongitudinaldirection ofthe
beam. whereverapplicable,shall also beconsideredin
the design of the beam.
24.3.1 For the purpose of calculation of
momentsin
slabs inamonolithic structure,itwillgenerallybe
sufficientlyaccurateto assumethatmembersconnected
to the ends of such slabs are fixed in position and
direction at
theendsremote from their connections
with the slabs.
24.3.1SlabsCarrying ConcentratedLoad
24.3.2.1Ifa solidslabsupportedon twooppositeedges,
carriesconcentratedloads the maximum bending
moment caused
bythe concentrated loads shall be
assumed to be resisted by an effective width of slab
(measuredparallel to the supportingedges)asfollows:
a) For a single concentrated load. the effective
width shall
becalculated in accordancewith the
following equation provided that it shall not
exceedthe actual width of the slab:
ber=kx(1-
..!..)+a
lef
where
b
d=effective width of slab,
k=constanthavingthe valuesgiveninTable
14depending upon the ratio of the width
oftheslab
(/~to the effective spanIe{,
x=distanceof thecentroidofthe
concentrated
loadfromnearersupport,
I
r f=effective span, and
a=widthof the contactareaofthe
concentrated load from nearer support
measured parallel to the supportededge.
And provided further that in case of a load near
the unsupported edge of a slab. the effective
width shall not exceed the above value nor half
theabovevalueplusthedistanceoftheloadfrom
theunsupportededge.
b) For two or more concentrated loads placed in a
line in the direction of
thespan, the bending
momentpermetrewidth of slab shall be
calculated separately for each loadaccordingto
its appropriateeffectivewidthof slab calculated
as in (a) above and added together for design
calculations.
40
0.1
0.2
0.3
0.4
O.S
0.6
0.7
0.8
0.9
1.0
andabove
ilorSlmpl,
SupportedS....
0.4
0.8
1.16
1.48
1.72
1.96
2.12
2.24
2.36
2.48
ilorCoatlDUQUI
51••
0.4
0.8
1.16
1.44
1.68
1.84.
1.96
2.08
2.16
2.24
24.3.2.3Anyotherrecognizedmethodof analysisfor
Caselof Ilabacoveredby24.3.%.1and24.3.2.2and
fotallothet~ase8of slabsmaybeused with the
approvaiOfaMengineer*in-charge.
24.3.2.4ThecritidilMedonforcheckingshearshall
beasJivenin34.2.4.1.
24.4SlabsSpaDllinllD twoDirectionsatRllbt
ADII_
Theslabsspanningin two directions at rightangles
andcarryinSuniformlydistributedload may be
desilnedbyanyacceptabletheoryor byusina
coefficientslivenin AnnexD. Fordetermining
bendingmomentsin slabs spanningin twodirections
atrightanalesandcarryingcoaeentreredload, any
acceptedmethod approvedbytheengineer-In-charge
maybeadopted.
NOTS-TheIDOIIcommonlyUJedelasticmethodsarebased
onApaud',orWester-pard',theoryandthemostcommonly
uledlimitItaJeofcoUapsemethodisbasedonJohansen'syield-
linetheory.
14.4.1RestrainedSlabwithUnequalConditionsat
AdjacentPan,I,
In some cases the support moments calculatedfrom
Table26 foradjacent panelsmaydiffersignificantly.
Thefollowingproceduremaybeadopted to adjust
them:
a)Calculatethesum ofmoments atmidspan and
IUpports(nea1ectingsigns).
b)treatthevaluesfromTable26 asfixedend
m<mieDts.
c) AccordingtCJtherelativestiffnessof adjacent
spans, distribute the fixed endmomentsacross
the supports,livingnew supportmoments.
d)Adjultmidspanmomentsuchthat, whenadded
to
thesupport moments from (c)(neglecting
IS456:
2000
signs),the totalshouldbeequal to that from (a).
If the resulting support moments are
signifi
cantly greaterthan the value fromTable26, the
tension
steeloverthesupports will need tobe
extended further. The procedure should
beas
follows:
1) Take
thespanmomentasparabolicbetween
supports:
itsmaximum value is as found
from
(d).
2)
Determinethepointsofcontraflexureof the
new
supportmoments [from (c)]withthe
span moment[from (1)].
3) Extendhalfthesupporttensionsteelat each
end to at least an effective depthor12 bar
diameters beyond the nearest point of
contraflexure.
4)Extend
thefull area of the support tension
steel at each end to half the distance from
(3).
24.5Loadson SuPportiDIBeams
The loads on beams supporting solid slabs spanning
in two directions at right angles andsupporting
uniformlydistributedloads, maybeassumedtobe in
accordancewithFig. 7.
25COMPRESSION MEMBERS
25.1Definitions
25.1.1Columnorstrutis a compressionmember,the
effectivelengthof whichexceedsthree timestheleast
lateraldimension.
25.1.2ShortandSlenderCompressionMembers
Acompressionmember maybeconsidered as short
· Ih
whenboththeslenderncb;~o.Dandbareless
than12:
A
2116818/07-1
LOADINTHISSHADED
AREATOBECARRIED
8VBEAM'e'
LOADINTHISSHADEDAREA
TO BECARRIEDBYBEAN'//
FlO.7LOADCARRJIIDBYSUPPORTINGBEAMS
41
B
Caselof Ilabacoveredby24.3.%.1and24.3.2.2and
fotallothet~ase8of slabsmaybeused with the
approvaiOfaMengineer*in-charge.
24.3.2.4ThecritidilMedonforcheckingshearshall
beasJivenin34.2.4.1.
24.4SlabsSpaDllinllD twoDirectionsatRllbt
ADII_
Theslabsspanningin two directions at rightangles
andcarryinSuniformlydistributedload may be
desilnedbyanyacceptabletheoryor byusina
coefficientslivenin AnnexD. Fordetermining
bendingmomentsin slabs spanningin twodirections
atrightanalesandcarryingcoaeentreredload, any
acceptedmethod approvedbytheengineer-In-charge
maybeadopted.
NOTS-TheIDOIIcommonlyUJedelasticmethodsarebased
onApaud',orWester-pard',theoryandthemostcommonly
uledlimitItaJeofcoUapsemethodisbasedonJohansen'syield-
linetheory.
14.4.1RestrainedSlabwithUnequalConditionsat
AdjacentPan,I,
In some cases the support moments calculatedfrom
Table26 foradjacent panelsmaydiffersignificantly.
Thefollowingproceduremaybeadopted to adjust
them:
a)Calculatethesum ofmoments atmidspan and
IUpports(nea1ectingsigns).
b)treatthevaluesfromTable26 asfixedend
m<mieDts.
c) AccordingtCJtherelativestiffnessof adjacent
spans, distribute the fixed endmomentsacross
the supports,livingnew supportmoments.
d)Adjultmidspanmomentsuchthat, whenadded
to
thesupport moments from (c)(neglecting
IS456:
2000
signs),the totalshouldbeequal to that from (a).
If the resulting support moments are
signifi
cantly greaterthan the value fromTable26, the
tension
steeloverthesupports will need tobe
extended further. The procedure should
beas
follows:
1) Take
thespanmomentasparabolicbetween
supports:
itsmaximum value is as found
from
(d).
2)
Determinethepointsofcontraflexureof the
new
supportmoments [from (c)]withthe
span moment[from (1)].
3) Extendhalfthesupporttensionsteelat each
end to at least an effective depthor12 bar
diameters beyond the nearest point of
contraflexure.
4)Extend
thefull area of the support tension
steel at each end to half the distance from
(3).
24.5Loadson SuPportiDIBeams
The loads on beams supporting solid slabs spanning
in two directions at right angles andsupporting
uniformlydistributedloads, maybeassumedtobe in
accordancewithFig. 7.
25COMPRESSION MEMBERS
25.1Definitions
25.1.1Columnorstrutis a compressionmember,the
effectivelengthof whichexceedsthree timestheleast
lateraldimension.
25.1.2ShortandSlenderCompressionMembers
Acompressionmember maybeconsidered as short
· Ih
whenboththeslenderncb;~o.Dandbareless
than12:
A
2116818/07-1
LOADINTHISSHADED
AREATOBECARRIED
8VBEAM'e'
LOADINTHISSHADEDAREA
TO BECARRIEDBYBEAN'//
FlO.7LOADCARRJIIDBYSUPPORTINGBEAMS
41
B
IS 456 :2000
where
1
M
=effectivelength in respect of the major
axis,
D ==depth inrespectof themajor axis,
I- effective length in respect of the minor
ry
axis,and
b=width of the member,
Itshallotherwisebeconsideredas aslender
compression member,
25.1.3UnsupportedLength
The unsupported length,I,of a compression member .
shall he takenasthecleardistancebetween end
restraints except that:
a)in flat slabconstruction,itshallbecleardistance
between the floor and the lower extremity of
thecapital, the droppanelorslabwhichever is
the least.
h)inbeam andslabconstruction,itshall be the
cleardistancebetweenthefloorandthe
underside of the shallower beam framing into
thecolumnsineachdirection at the next higher
floor
level.
c) in columns
restrainedlaterallybystruts,itshall
bethecleardistancebetweenconsecutive
strutsin each vertical plane, provided that to be
anadequatesupport,twosuchstrutsshall
meet the columns at approximately the
same
level
andtheangle between verticalplanes
through the struts shall notvarymorethan3Qt'
from a right angle. Suchstrutsshall be of
adequate dimensions and shall have
sufficientanchorageto restrain the member against lateral
deflection.
d)incolumnsrestrainedlaterally bystruts or
beams,
withbracketsused at thejunction,itshall
be
theclear distance between thefloor andthe
lower edge of the bracket, provided that the
bracket width equals that of the beam strut and
isat least half that of the colurnn.
25.2EffectiveLengthofCompressionMembers
In the absenceofmore exact analysis,theeffective
lengthler'of columnsmaybeobtained as described in
AnnexE.
25.3SlendernessLimitsforColumns
25.3.1 Theunsupportedlength between end restraints
shallnotexceed60 times the leastlateraldimension
of a column.
25.3.2If,in any givenplane,one end ofa columnis
unrestrained, its unsupportedlength,itshallnotexceed
JOOb
2
---'
[)
where
b=width-of that cross-section, and
D=depthof thecross-sectionmeasuredinthe
plane underconsideration.
25.4MinimumEccentricity
Allcolumnsshallbe designedformmrmum
eccentricity,equaltotheunsupported lengthofcolumn!
500 pluslateraldimensions/30, subjectto a minimum
of 20
rom.Wherebi-axialbendingisconsidered,it is
sufficienttoensurethateccentricityexceedsthe
minimumabout one axis at a time.
26REQUIREMENTS GOVERNING
REINFORCEMENTANDDETAILING
26.1 General
Reinforcingsteelof sametypeand
gradeshallbe used
asmainreinforcementin astructuralmember.
However.simultaneoususe oftwo differenttypes or
gradesof steel for mainandsecondaryreinforcement
respectively is permissible.
26.1.1Bars may be arranged
singly.or in pairs in
contact,orin groups of three or four barsbundledin
contact.Bundledbarsshall beenclosedwithinstirrups
orties.Bundled barsshallbe tied together to ensure
the bars remaining
together.Bars larger than 32 mm
diametershall not be
bundled.exceptin columns.
26.1.2Therecommendationsfordetailingfor
earthquake-resistant construction given in IS 13920
should be taken
intoconsideration,where applicable
(see also
IS 4326).
26.2Development ofStressinReinforcement
Thecalculatedtension or compression inanybarat
anysection shall be developed on each side of the
section
byan appropriatedevelopmentlength or
end
anchorageor byacombinationthereof.
26.2.1DevelopmentLength
of
Bars
The developmentlengthL
d
is givenby
L
_,a.
(1---
4fbd
where
,=nominaldiameter ofthebar,
a~=stressinbaratthesectionconsideredatdesign
load,and
t
hd=design bond stress given in26.Z.1.1.
NOTES
1ThedevelopmentIcnJlhincludcaanchomaevDluesofhooks
intensionreinforcement.
2Forbarsofsectionsotherthancireular.thedevelopment
lenathshouldbesufficienttodevelopthestrasinthebar
bybone"
0°'
...",,:
.....'lI
42
I,
:i
.c.
.;.
where
1
M
=effectivelength in respect of the major
axis,
D ==depth inrespectof themajor axis,
I- effective length in respect of the minor
ry
axis,and
b=width of the member,
Itshallotherwisebeconsideredas aslender
compression member,
25.1.3UnsupportedLength
The unsupported length,I,of a compression member .
shall he takenasthecleardistancebetween end
restraints except that:
a)in flat slabconstruction,itshallbecleardistance
between the floor and the lower extremity of
thecapital, the droppanelorslabwhichever is
the least.
h)inbeam andslabconstruction,itshall be the
cleardistancebetweenthefloorandthe
underside of the shallower beam framing into
thecolumnsineachdirection at the next higher
floor
level.
c) in columns
restrainedlaterallybystruts,itshall
bethecleardistancebetweenconsecutive
strutsin each vertical plane, provided that to be
anadequatesupport,twosuchstrutsshall
meet the columns at approximately the
same
level
andtheangle between verticalplanes
through the struts shall notvarymorethan3Qt'
from a right angle. Suchstrutsshall be of
adequate dimensions and shall have
sufficientanchorageto restrain the member against lateral
deflection.
d)incolumnsrestrainedlaterally bystruts or
beams,
withbracketsused at thejunction,itshall
be
theclear distance between thefloor andthe
lower edge of the bracket, provided that the
bracket width equals that of the beam strut and
isat least half that of the colurnn.
25.2EffectiveLengthofCompressionMembers
In the absenceofmore exact analysis,theeffective
lengthler'of columnsmaybeobtained as described in
AnnexE.
25.3SlendernessLimitsforColumns
25.3.1 Theunsupportedlength between end restraints
shallnotexceed60 times the leastlateraldimension
of a column.
25.3.2If,in any givenplane,one end ofa columnis
unrestrained, its unsupportedlength,itshallnotexceed
JOOb
2
---'
[)
where
b=width-of that cross-section, and
D=depthof thecross-sectionmeasuredinthe
plane underconsideration.
25.4MinimumEccentricity
Allcolumnsshallbe designedformmrmum
eccentricity,equaltotheunsupported lengthofcolumn!
500 pluslateraldimensions/30, subjectto a minimum
of 20
rom.Wherebi-axialbendingisconsidered,it is
sufficienttoensurethateccentricityexceedsthe
minimumabout one axis at a time.
26REQUIREMENTS GOVERNING
REINFORCEMENTANDDETAILING
26.1 General
Reinforcingsteelof sametypeand
gradeshallbe used
asmainreinforcementin astructuralmember.
However.simultaneoususe oftwo differenttypes or
gradesof steel for mainandsecondaryreinforcement
respectively is permissible.
26.1.1Bars may be arranged
singly.or in pairs in
contact,orin groups of three or four barsbundledin
contact.Bundledbarsshall beenclosedwithinstirrups
orties.Bundled barsshallbe tied together to ensure
the bars remaining
together.Bars larger than 32 mm
diametershall not be
bundled.exceptin columns.
26.1.2Therecommendationsfordetailingfor
earthquake-resistant construction given in IS 13920
should be taken
intoconsideration,where applicable
(see also
IS 4326).
26.2Development ofStressinReinforcement
Thecalculatedtension or compression inanybarat
anysection shall be developed on each side of the
section
byan appropriatedevelopmentlength or
end
anchorageor byacombinationthereof.
26.2.1DevelopmentLength
of
Bars
The developmentlengthL
d
is givenby
L
_,a.
(1---
4fbd
where
,=nominaldiameter ofthebar,
a~=stressinbaratthesectionconsideredatdesign
load,and
t
hd=design bond stress given in26.Z.1.1.
NOTES
1ThedevelopmentIcnJlhincludcaanchomaevDluesofhooks
intensionreinforcement.
2Forbarsofsectionsotherthancireular.thedevelopment
lenathshouldbesufficienttodevelopthestrasinthebar
bybone"
0°'
...",,:
.....'lI
42
I,
:i
.c.
.;.
IS456:2000
16.2.1.1Designbondstress inlimitstatemethodfor plain bars intensionshall be asbelow:
Gradeofconcrete
DesignbondstreSJ,
f
hd
,
N/mm
2
M20
1.2
M25
1.4
M30
1.5
M35
1.7
M 40 andabove
1.9
For deformed bars conforming to IS 1786these values
shallbeincreasedby60 percent.
For bars in compression.thevalues of bond stress for
bars in tension shall be increased
by25 percent.
The
valuesof bond stress in working stress design,
aregivenin B-2.1.
26.2.1.2Barsbundled;11contact
The developmentlengthofeachbar ofbundledbars
shall be that for the individual bar, increased
by )0
percent
fortwobars incontact,20 percentfor three
bars·incontactand 33 percentfor fourbarsin contact.
26.2.2 Anchoring Reinforcing
Bars
26.2.2.1Anchoringbarsintension
a)Deformedbarsmaybe usedwithoutend
anchoragesprovideddevelopmentlength
requirementissatisfied.Hooks should normally
heprovidedfor plainbarsin tension.
b)Bendsandhooks-Bendsandhooksshall
conformto IS2502
J)Bends-Theanchoragevalue of bendshall
be takenas4 times thediameterof thebar
for each45
t
'bend subject to amaximumof
16 times the diameter of the bar.
2)
Hooks-Theanchorage value of a standard
U-type
hookshallbe equaltoJ6timesthe
diamet.erofthe bar.
26.2.2.2Anchoringbars incompression
The anchoragelengthofstraight bar incompression
shall beequalto thedevelopment lengthofbarsin
compressionasspecifiedin26.2..1.Theprojected
length of hooks, bends
andstraightlengthsbeyond
bendsifprovided for a bar incompression,shall only
be
consideredfor development length.
16.2.2.3Mechanicaldevices[oranchorage
Anymechanical or other device capable of developing
thestrengthofthebarwithoutdamagetoconcretemay
be used asanchoragewiththeapprovalof theengineer
in-charge.
26.2.2.4Anchoringshearreinforcement
a)Inclinedbars- The development lengthshan
be as for bars intension; this lengthshall be
measured as under:
1) In tension zone, from the end of thesloping
Ofinclinedportionofthe bar,and
2) In thecompressionzone,frontthe middepth
of the beam.
b)Stirrups-Notwithstandinganyofthe
provisionsofthisstandard,incaseofsecondary
reintorcement, such as stirrups and transverse
ties,completedevelopmentlengthsand
anchorageshallbedeemedtohavebeen
provided when the barisbentthroughanangle
of at least90"roundabarofat leastitsown
diameter
and iscontinuedbeyondtheendofthe
curve for alengthofat least eight diameters, or
when the bar is bent
throughan angle of
135
0
and iscontinuedbeyondtheendof the curve
for alengthofatleastsixbar diameters orwhen
the bar is bentthrough anangleof 1HO°andis
continuedbeyond theend of thecurvefora
length ofat leastfour bardiameters.
26.2.2.5 Bearingstressesatbends
The
hearingstressinconcreteforbendsandhooks
describedin IS 2502 neednot be checked. The bearing
stressinsideabendinanyother bendshall be calculated
as given below:
F
ht
Bearingstress =
rei>
where
}/'ol=:tensile force duetodesignloads in a bar
orgroupofhal's,
,. =internal radius of the bend, and
¢=sizeof the bar or, in bundle. the size of har
of
equivalentarea.
For limit stale method ofdesign,this stress shall
not
I.5f~kt+'h h..
exceed Wierer.kISte.caractensuccube
1+2~/a C·
strengthofconcreteanda,for aparticularburorgroup
of hars incontactshallhetaken asthecentretocentre
distance between bars or groups of barsperpendicular
to theplaneof thebend;for a bar Ofgroupof
bars adjacent to the face of the memberashall he
takenasthe cover plus size ofbar(q».Forworking
'stressmethodofdesign.thebearingstressshall
not exceed--~.
J+2c/J/a
26.2.2.6If achangeindirectionoftensionor
compressionreinforcement inducesaresultantforce
acting outward tending tosplit theconcrete,such force
16.2.1.1Designbondstress inlimitstatemethodfor plain bars intensionshall be asbelow:
Gradeofconcrete
DesignbondstreSJ,
f
hd
,
N/mm
2
M20
1.2
M25
1.4
M30
1.5
M35
1.7
M 40 andabove
1.9
For deformed bars conforming to IS 1786these values
shallbeincreasedby60 percent.
For bars in compression.thevalues of bond stress for
bars in tension shall be increased
by25 percent.
The
valuesof bond stress in working stress design,
aregivenin B-2.1.
26.2.1.2Barsbundled;11contact
The developmentlengthofeachbar ofbundledbars
shall be that for the individual bar, increased
by )0
percent
fortwobars incontact,20 percentfor three
bars·incontactand 33 percentfor fourbarsin contact.
26.2.2 Anchoring Reinforcing
Bars
26.2.2.1Anchoringbarsintension
a)Deformedbarsmaybe usedwithoutend
anchoragesprovideddevelopmentlength
requirementissatisfied.Hooks should normally
heprovidedfor plainbarsin tension.
b)Bendsandhooks-Bendsandhooksshall
conformto IS2502
J)Bends-Theanchoragevalue of bendshall
be takenas4 times thediameterof thebar
for each45
t
'bend subject to amaximumof
16 times the diameter of the bar.
2)
Hooks-Theanchorage value of a standard
U-type
hookshallbe equaltoJ6timesthe
diamet.erofthe bar.
26.2.2.2Anchoringbars incompression
The anchoragelengthofstraight bar incompression
shall beequalto thedevelopment lengthofbarsin
compressionasspecifiedin26.2..1.Theprojected
length of hooks, bends
andstraightlengthsbeyond
bendsifprovided for a bar incompression,shall only
be
consideredfor development length.
16.2.2.3Mechanicaldevices[oranchorage
Anymechanical or other device capable of developing
thestrengthofthebarwithoutdamagetoconcretemay
be used asanchoragewiththeapprovalof theengineer
in-charge.
26.2.2.4Anchoringshearreinforcement
a)Inclinedbars- The development lengthshan
be as for bars intension; this lengthshall be
measured as under:
1) In tension zone, from the end of thesloping
Ofinclinedportionofthe bar,and
2) In thecompressionzone,frontthe middepth
of the beam.
b)Stirrups-Notwithstandinganyofthe
provisionsofthisstandard,incaseofsecondary
reintorcement, such as stirrups and transverse
ties,completedevelopmentlengthsand
anchorageshallbedeemedtohavebeen
provided when the barisbentthroughanangle
of at least90"roundabarofat leastitsown
diameter
and iscontinuedbeyondtheendofthe
curve for alengthofat least eight diameters, or
when the bar is bent
throughan angle of
135
0
and iscontinuedbeyondtheendof the curve
for alengthofatleastsixbar diameters orwhen
the bar is bentthrough anangleof 1HO°andis
continuedbeyond theend of thecurvefora
length ofat leastfour bardiameters.
26.2.2.5 Bearingstressesatbends
The
hearingstressinconcreteforbendsandhooks
describedin IS 2502 neednot be checked. The bearing
stressinsideabendinanyother bendshall be calculated
as given below:
F
ht
Bearingstress =
rei>
where
}/'ol=:tensile force duetodesignloads in a bar
orgroupofhal's,
,. =internal radius of the bend, and
¢=sizeof the bar or, in bundle. the size of har
of
equivalentarea.
For limit stale method ofdesign,this stress shall
not
I.5f~kt+'h h..
exceed Wierer.kISte.caractensuccube
1+2~/a C·
strengthofconcreteanda,for aparticularburorgroup
of hars incontactshallhetaken asthecentretocentre
distance between bars or groups of barsperpendicular
to theplaneof thebend;for a bar Ofgroupof
bars adjacent to the face of the memberashall he
takenasthe cover plus size ofbar(q».Forworking
'stressmethodofdesign.thebearingstressshall
not exceed--~.
J+2c/J/a
26.2.2.6If achangeindirectionoftensionor
compressionreinforcement inducesaresultantforce
acting outward tending tosplit theconcrete,such force
IS456:2000
shouldbetakenupbyadditionallinkaorstirrups.Bent
tensionbar at a re-entrantangleshouldbeavoided.
26.2.3Curtailment01relll;on-R~;nforce",,"t ill
FlexuralMember,
26.2.3.1Forcurtailment.reinforcement.baIleltead
beyondthe point at which it is nolonlerrequiredto
resistflexureforadistanceequaltotheeffectivedepth
of thememberor 12timesthebardiameter,whichever
. is greaterexceptatsimplesupportorendofcantilever.
Inaddition26.2.3.2to26.2.3.5.hall alsobesatisfied.
NOTE-ApointatwhichreinforcementI,80loftpl'required
to resistflexureiswheretheresistancemoment oflht1eCti0ll,
consideringonlythecontinuinlban,isequaltothedeaip
moment.
26.1.3.2Flexuralreinforcementshallnotbetenninated
in a tension zone unless
anyoneof the following
conditionsis
satisfied:
a) The shear at the cut-off point does not
exceed
two-thirdsthat permitted, includinltheshear
strengthof web reinforcementprovided.
b) Stirruparea in excessof thatrequiredforshear
andtorsionisprovidedalongeachtennlnated
baroveradistancefromthecut-offpointequal
tothree-fourthsthe effective depth of the
member.Theexcessstinupareashall benot
lessthan 0.4bIll"wherebis the breadth of
beam.sis thespacingand[,isthecharacteristic
strengthofreinforcemC:ntinN/mm
2
•
The
resultingspacingshall notexceed
dIs
Pitwhere
Phis the ratio ofthearea ofbancut-offto the
total area of bars at the section, and
dis the
effectivedepth.
c) For 36rnmandsmallerbars,thecontinuingbars
providedouble the area requiredforflexureat
the cut-offpointandthesheardoesnotexceed
three-fourthsthatpermitted.
16.1.3.3Positivemomentreinforcement
a)Atleastone-thirdthepositive moment
reinforcement in simple members andone
fourth the positive momentreinforcementin
continuousmembersshallextendalongthesame
face ofthememberintothesupport,to a length
equal toL
d/3.
b) When a flexuralmemberispartoftheprimary
lateralloadresisting system,thepositive
reinforcementrequiredtobeextendedintothe
supportasdescribedin (a) shallbeanchoredto
develop its design stress intensionattheface
of the support.
c)
Atsimple supportsand at points ofinftection,
positivemomenttension
reinforcemeatshallbe
limitedto adiametersuchthat L
d
computedfor
!.Jby26.2.1doesnotexceed
-...--
M,'*.....-oflUiltllCeoftilesection
.......,IllNillforc.a.entatabeaecdOD
to......tot..;
ttl•0.871,IntbIc...ofliJpitsJatedesip
andthOpenni••ible...(J.in-thecase
ofworkingStrolldeillft;
V=shearforceatthesectiondue'todesip
loads;
L
o=sumoftheanchoragebeyondthecentre
ofthesupport and theequivalent
,p~J1orale valueofanyhook or
mNhan~~ge atsimplesupport;
andatapointlitiltlWURaJ,b
R
islimited
totheeffecdvodopthofdie""m~1lPJ
12;,whicheverispater;and
;=diameterofbar.
ThevalueofM./Vintheaboveexpressionmaybe
incr••,adby30percentwhen the endsofthe
reinforCOlftO,;r....~OJJtinedbyacompressivereaction.
26.2.3.4Ntgativemoment,,;nforcernent
Atleatone-thirdof the~JaI ~inforc~nt provided
fornepaviJIJOIft8tItIldtflUPPOJtsballextendbeyond
thepointofi"fbJodo"forIt4jstaneenot lessthanthe
effectivedepthofthlmom'*of12,orone-sixteenth
oftheclearspanwhichov"i,8f8*.
26.2.3.5Curtai"",,,'ofbUNII.dbar,
Bars in a bundle shallterminateatdifforln~points
spacedapartbynotleiSthan40timesthebardiamoter
exceptforbundlesItoppin.at asupport.
26.1.4SpecialM,mber!
Adequateendanchoraloshallbeprovidodfor.",10"
reinforcementinflexuralmembenwhereroinfOJlJO"
mcntstressisnotdirecdyproportionaltomOlMltl,
suchassloped.ltepped,ortaperedfootinp;brackets;
deepbeams;andmembersin whichthetension
reinforcementisnotparalleltothecomprel.ionfICO.
26.%.5R,inforclmentSpllcin,
Wheresplicesareprovidedinthereinforcinlban.they
shalluf.81possiblebeawayfromtheIeCUonlof
maximumItreS'andbeltagered.Itiancommendod
thatsplicesinflexuralmembenIhould"Olbfat
sectionswhorethebendinlmomenti.morethan'0
percentofthemomentofresistance;andnotmONChan
halfthe barsshallbesplicedatasection.
Wheremorethanone·balfofthobanaresplicedata
section or wberesplicesaremad.Itpoint.of
maximumstress,specialprecaution.shallboeaken,
44
shouldbetakenupbyadditionallinkaorstirrups.Bent
tensionbar at a re-entrantangleshouldbeavoided.
26.2.3Curtailment01relll;on-R~;nforce",,"t ill
FlexuralMember,
26.2.3.1Forcurtailment.reinforcement.baIleltead
beyondthe point at which it is nolonlerrequiredto
resistflexureforadistanceequaltotheeffectivedepth
of thememberor 12timesthebardiameter,whichever
. is greaterexceptatsimplesupportorendofcantilever.
Inaddition26.2.3.2to26.2.3.5.hall alsobesatisfied.
NOTE-ApointatwhichreinforcementI,80loftpl'required
to resistflexureiswheretheresistancemoment oflht1eCti0ll,
consideringonlythecontinuinlban,isequaltothedeaip
moment.
26.1.3.2Flexuralreinforcementshallnotbetenninated
in a tension zone unless
anyoneof the following
conditionsis
satisfied:
a) The shear at the cut-off point does not
exceed
two-thirdsthat permitted, includinltheshear
strengthof web reinforcementprovided.
b) Stirruparea in excessof thatrequiredforshear
andtorsionisprovidedalongeachtennlnated
baroveradistancefromthecut-offpointequal
tothree-fourthsthe effective depth of the
member.Theexcessstinupareashall benot
lessthan 0.4bIll"wherebis the breadth of
beam.sis thespacingand[,isthecharacteristic
strengthofreinforcemC:ntinN/mm
2
•
The
resultingspacingshall notexceed
dIs
Pitwhere
Phis the ratio ofthearea ofbancut-offto the
total area of bars at the section, and
dis the
effectivedepth.
c) For 36rnmandsmallerbars,thecontinuingbars
providedouble the area requiredforflexureat
the cut-offpointandthesheardoesnotexceed
three-fourthsthatpermitted.
16.1.3.3Positivemomentreinforcement
a)Atleastone-thirdthepositive moment
reinforcement in simple members andone
fourth the positive momentreinforcementin
continuousmembersshallextendalongthesame
face ofthememberintothesupport,to a length
equal toL
d/3.
b) When a flexuralmemberispartoftheprimary
lateralloadresisting system,thepositive
reinforcementrequiredtobeextendedintothe
supportasdescribedin (a) shallbeanchoredto
develop its design stress intensionattheface
of the support.
c)
Atsimple supportsand at points ofinftection,
positivemomenttension
reinforcemeatshallbe
limitedto adiametersuchthat L
d
computedfor
!.Jby26.2.1doesnotexceed
-...--
M,'*.....-oflUiltllCeoftilesection
.......,IllNillforc.a.entatabeaecdOD
to......tot..;
ttl•0.871,IntbIc...ofliJpitsJatedesip
andthOpenni••ible...(J.in-thecase
ofworkingStrolldeillft;
V=shearforceatthesectiondue'todesip
loads;
L
o=sumoftheanchoragebeyondthecentre
ofthesupport and theequivalent
,p~J1orale valueofanyhook or
mNhan~~ge atsimplesupport;
andatapointlitiltlWURaJ,b
R
islimited
totheeffecdvodopthofdie""m~1lPJ
12;,whicheverispater;and
;=diameterofbar.
ThevalueofM./Vintheaboveexpressionmaybe
incr••,adby30percentwhen the endsofthe
reinforCOlftO,;r....~OJJtinedbyacompressivereaction.
26.2.3.4Ntgativemoment,,;nforcernent
Atleatone-thirdof the~JaI ~inforc~nt provided
fornepaviJIJOIft8tItIldtflUPPOJtsballextendbeyond
thepointofi"fbJodo"forIt4jstaneenot lessthanthe
effectivedepthofthlmom'*of12,orone-sixteenth
oftheclearspanwhichov"i,8f8*.
26.2.3.5Curtai"",,,'ofbUNII.dbar,
Bars in a bundle shallterminateatdifforln~points
spacedapartbynotleiSthan40timesthebardiamoter
exceptforbundlesItoppin.at asupport.
26.1.4SpecialM,mber!
Adequateendanchoraloshallbeprovidodfor.",10"
reinforcementinflexuralmembenwhereroinfOJlJO"
mcntstressisnotdirecdyproportionaltomOlMltl,
suchassloped.ltepped,ortaperedfootinp;brackets;
deepbeams;andmembersin whichthetension
reinforcementisnotparalleltothecomprel.ionfICO.
26.%.5R,inforclmentSpllcin,
Wheresplicesareprovidedinthereinforcinlban.they
shalluf.81possiblebeawayfromtheIeCUonlof
maximumItreS'andbeltagered.Itiancommendod
thatsplicesinflexuralmembenIhould"Olbfat
sectionswhorethebendinlmomenti.morethan'0
percentofthemomentofresistance;andnotmONChan
halfthe barsshallbesplicedatasection.
Wheremorethanone·balfofthobanaresplicedata
section or wberesplicesaremad.Itpoint.of
maximumstress,specialprecaution.shallboeaken,
44
suchasincreasingthelengthof lapand/oruSlnSspirals
orclosely-spacedstirrupsaround the length of the
splice.
-.u.lLap,plie"
a) Lapsplicesshallnotbeusedforbarslargerthan'
36rom;for largerdiameters,barsmaybe
welded(see12.4);incaseswhereweldingis
not practicable, lapping of bars larger than
36
mmmaybepermitted,in which case
additionalspiralsshouldbe providedaroundthe
lappedbars.
b) Lap splices shallbeconsideredasstaggered if
the centre tocentre distanceof the splices is
notJessthan 1.3timesthe laplengthcalculated
asdescribed in (e).
c) Lap lengthincludinganchoragevalueof
hooks
for bars in flexural tension shallbe
L
d
tse«
26.2.1)or30(/)whicheverisgreater
and for direct tension
shallbe
2L
d
or30~
whicheverisgreater.The straightlengthof the
lapshallnotbeJessthanIS,or 200mm.The
followingprovisionsshall also apply:
Wherelapoccursforatensionbarlocatedat:
I) top of a section8Scastand theminimumcover
is less than twice the diameter of the
lapped
bar,the lap lengthshallbeincreased bya factor
of 1.4.
2)comer of a section and theminimumcover to
either face
islessthan twice the diameter of
the lapped bar or where the clear distance
betweenadjacentlaps is less than7Smm or 6
times the diameterof lappedbar.whicheveris
greater,the lap lengthshould
beincreasedbya
factorof ).4.'
Wherebothcondition(1) and(2)
apply.thelap
length
shouldbeincreasedbyafactorof2.0.
NOTE-Splicesia tension members
shallbeenclosed in
spiralsmadeofbonDOllessthan6 mmdiameterwithpitch
. notlnofethan 100mm.
d) The laplengthincompressionshan beequalto
thedevelopment length incompression,
calculated as described in~.1.1.but notless
than24~.
e) When bars oftwo differentdiameters aretobe
spliced, the laple"gthshallbecalculatedon
the basis of diameterof the smaller
bar.
t)When splicing of welded wirefabricis tobe
carried out, lap splices of wiresshallbemade
so that overlapmeasured
betweenthe
extreme
cross wiresshallbe notlessthanthespacingof
prosswiresplus100mm,
_>Incase ofb"ndlodbars, lapped splices of
l1""dtcdbanshallbemadebysplicingone bar
IS456:~
atatime;suchindividualspliceswithina bundle
shall bestaggered.
16.1.5.2Strengtho/welds
Thefollowingvalues maybeusedwherethestrength
ofthewe1dhasbeenproYedbyteststobeat least as
great1$d1~ofthoparentbar..'
a)Splices'incompression-For weldedsplices
andmechanicalconnection, 100percentof the
desis"strengthofjoined bars.
b)Splicesintension
I)80percentofthe design strengthof welded
bars (100
percent if weldingisItrictly
supervisedand if at anycross
...aectionof the
member notmorethan20percentof the
tensilereinf(lr~tnent iswelded).
2)\00pcf~ntof design strength of mecha-
nicalconnection.
16.2.5.3End-bearingsplices
End-hearingsplices shall beused only for bars in
compression.Theends of
thebarsshallbesquarecut
andconcentricbeari
ngensuredbysuitabledevices.
16.3SpacinlofRelnloreenaent
26.3.1For thepurposeofthis~I.-"se.thediametorof
around bar shallbeitsn011\"'"diamoto"and inthe
case of barsw~ich ~rono,roundorinthocase of
deformedbars orcrimpod~Itthodiamotershallbe
takenasthe<l,,,~etefofaoifcle.ivinJanequivalent
effecti vearcs".WheroIpacin.limitationsand
minimumCO"QfOtccover(I"Z6A)arebuedonbar
diameter.agroupofbanbundledincontactshallbe
treatedas alinslobar ofdiameterderivedfromthe
total~quiY_'enl aroa.
J6.3.1MinimumDistanceBetweenIndividUfJIBars
Thefollowi"gshallapplyfor.pacinlof ban:
a) The_orizontaldistancebetweentwo parallel
main'reinforcinlbarsshallusuallybe not less
thantholreato.,ofthofoUowina:
I)ll-"di..meterofthobarifthediameteRare
e4l~alt
2)Th~diameterofthelarlerbarifthe
diamolCrsareunoqual.and
3)S111mmorothanthonominalmaximumsize
of~p~_IPlalO.
~OTB-This doesnotprecludetheuseorllllprsizeof
D.I",.itelbeyondtheconceatedreinfon:ementinthe
lAmemember;lheaize of,"relates,naybenaduoocl
Groundcon,cltedreinforcementtQcomplywiththil
provision.
b)Qreaterhorizontaldistancethan thominimum
specified in (a) shouldbeprov~dodwherevor
possible.Howeverwhenneedlevibratorsaro
45
orclosely-spacedstirrupsaround the length of the
splice.
-.u.lLap,plie"
a) Lapsplicesshallnotbeusedforbarslargerthan'
36rom;for largerdiameters,barsmaybe
welded(see12.4);incaseswhereweldingis
not practicable, lapping of bars larger than
36
mmmaybepermitted,in which case
additionalspiralsshouldbe providedaroundthe
lappedbars.
b) Lap splices shallbeconsideredasstaggered if
the centre tocentre distanceof the splices is
notJessthan 1.3timesthe laplengthcalculated
asdescribed in (e).
c) Lap lengthincludinganchoragevalueof
hooks
for bars in flexural tension shallbe
L
d
tse«
26.2.1)or30(/)whicheverisgreater
and for direct tension
shallbe
2L
d
or30~
whicheverisgreater.The straightlengthof the
lapshallnotbeJessthanIS,or 200mm.The
followingprovisionsshall also apply:
Wherelapoccursforatensionbarlocatedat:
I) top of a section8Scastand theminimumcover
is less than twice the diameter of the
lapped
bar,the lap lengthshallbeincreased bya factor
of 1.4.
2)comer of a section and theminimumcover to
either face
islessthan twice the diameter of
the lapped bar or where the clear distance
betweenadjacentlaps is less than7Smm or 6
times the diameterof lappedbar.whicheveris
greater,the lap lengthshould
beincreasedbya
factorof ).4.'
Wherebothcondition(1) and(2)
apply.thelap
length
shouldbeincreasedbyafactorof2.0.
NOTE-Splicesia tension members
shallbeenclosed in
spiralsmadeofbonDOllessthan6 mmdiameterwithpitch
. notlnofethan 100mm.
d) The laplengthincompressionshan beequalto
thedevelopment length incompression,
calculated as described in~.1.1.but notless
than24~.
e) When bars oftwo differentdiameters aretobe
spliced, the laple"gthshallbecalculatedon
the basis of diameterof the smaller
bar.
t)When splicing of welded wirefabricis tobe
carried out, lap splices of wiresshallbemade
so that overlapmeasured
betweenthe
extreme
cross wiresshallbe notlessthanthespacingof
prosswiresplus100mm,
_>Incase ofb"ndlodbars, lapped splices of
l1""dtcdbanshallbemadebysplicingone bar
IS456:~
atatime;suchindividualspliceswithina bundle
shall bestaggered.
16.1.5.2Strengtho/welds
Thefollowingvalues maybeusedwherethestrength
ofthewe1dhasbeenproYedbyteststobeat least as
great1$d1~ofthoparentbar..'
a)Splices'incompression-For weldedsplices
andmechanicalconnection, 100percentof the
desis"strengthofjoined bars.
b)Splicesintension
I)80percentofthe design strengthof welded
bars (100
percent if weldingisItrictly
supervisedand if at anycross
...aectionof the
member notmorethan20percentof the
tensilereinf(lr~tnent iswelded).
2)\00pcf~ntof design strength of mecha-
nicalconnection.
16.2.5.3End-bearingsplices
End-hearingsplices shall beused only for bars in
compression.Theends of
thebarsshallbesquarecut
andconcentricbeari
ngensuredbysuitabledevices.
16.3SpacinlofRelnloreenaent
26.3.1For thepurposeofthis~I.-"se.thediametorof
around bar shallbeitsn011\"'"diamoto"and inthe
case of barsw~ich ~rono,roundorinthocase of
deformedbars orcrimpod~Itthodiamotershallbe
takenasthe<l,,,~etefofaoifcle.ivinJanequivalent
effecti vearcs".WheroIpacin.limitationsand
minimumCO"QfOtccover(I"Z6A)arebuedonbar
diameter.agroupofbanbundledincontactshallbe
treatedas alinslobar ofdiameterderivedfromthe
total~quiY_'enl aroa.
J6.3.1MinimumDistanceBetweenIndividUfJIBars
Thefollowi"gshallapplyfor.pacinlof ban:
a) The_orizontaldistancebetweentwo parallel
main'reinforcinlbarsshallusuallybe not less
thantholreato.,ofthofoUowina:
I)ll-"di..meterofthobarifthediameteRare
e4l~alt
2)Th~diameterofthelarlerbarifthe
diamolCrsareunoqual.and
3)S111mmorothanthonominalmaximumsize
of~p~_IPlalO.
~OTB-This doesnotprecludetheuseorllllprsizeof
D.I",.itelbeyondtheconceatedreinfon:ementinthe
lAmemember;lheaize of,"relates,naybenaduoocl
Groundcon,cltedreinforcementtQcomplywiththil
provision.
b)Qreaterhorizontaldistancethan thominimum
specified in (a) shouldbeprov~dodwherevor
possible.Howeverwhenneedlevibratorsaro
45
IS 456 : 2000
usedthehorizontal distance betweenbars of a
groupmaybereducedtotwo-thirdsthe
nominal maximumsizeof the coarseaggregate,
provided that sufficient space is left between
groupsof bars toenable the vibrator to be
immersed.
c) Where there arc two or more rows of bars, the
bursshallhevertically in line and the minimum
verticaldistancebetween the bars shall be
15mrn,two-thirds the nominalmaximumsize
ofaggregateor the maximum size of bars,
whichever is greater.
26.3.3
Maxi/nun,DistanceBetweenBars inTension
Unless the calculation of crack widths shows that a
greaterspacing isacceptable,the followingrules shall
he applied to flexural members in normal internal or
external conditions of exposure.
a)Beams- Thehorizontal distance between
parallelreinforcement bars, or groups, ncarthe
tension face of a beam shall not be greater
than the value given in Table 15 depending on
the amount ofredistributioncarriedout in
analysisandthe characteristic strength of the
reinIorcement.
b)
Slabs
1) Thehorizontaldistancebetweenparallelmain
reinforcementbarsshallnotbemorethanthree
times the effective depth of solid slab or
300IntTIwhicheveris smaller.
2) The horizontal distance between parallel
reinforcementbarsprovidedagainst
shrinkageandtemperatureshall not be more
thanfive times the effectivedepth of a solid
slab or 450 mm whichever is
smaIJer.
26.4 NominalCovertoReinforcement
26.4.1NominalCover
Nominal cover is the design depth of concrete cover
to all steel reinforcements, including links. It is the
dimensionusedindesignand indicatedin thedrawings.
I
tshall benotless than the diameter of the bar.
26.4.2NominalCovertoMeetDurability
Requirement
Minimum values for the nominal cover of normal
weight aggregate concrete which should
beprovided
to all reinforcement, including links
dependingonthe
condition of exposure described in
8.2.3shall be as
given in Table 16.
26.4.2.1 However for alongitudinalreinforcing
bar in a column nominal cover shall in
anycase not
be less than 40 mm, or less than thediameterof
such bar. In the case
ofcolumnsofminimum
dimensionof 200 mmor under,whosereinforcing bars
do not exceed 12mm, a nominal cover of 25 mm
may
be used.
26.4.2.2 For footingsminimumcover shall be 50 mm.
26.4.3 Nominal Cover to
MeetSpecified Periodof
FireRe..sistance
Minimumvalues of nominal cover of normal-weight
aggregateconcrete to be provided to all reinforcement
includinglinks to meetspecifiedperiod
offire
resistance shall
begiven in Table 16A.
26.5RequirementsofReinforcement
for
StructuralMembers
26.5.1Beams
26.5.1.1Tensionreinforcement
a)Minimumreinforcement-Theminimumareaof
tensionreinforcementshall be not less than that
....
Table 15ClearDistance BetweenBars
tCtause26.3.3)
f).PercentageRedistribution to or fromSectionConsidered
-10 -15 0 +I~ +30
Clear Distance BetweenBan
NIJnln
2
nun mm mm mm mm
2~() 215 260 300 300300
415 12~ 15~ 180 210 235
500 105 130 150 17S 195
N()TE - Thespacingsgiven inthetablearenotapplicabletomemberssubjectedtoparticularlyagressiveenvironmentsunlessinthe
calculationof'the momentofresistance,I.,hasbeenlimitedto300N/mm
2
inlimitstartdesianondaliilimitedto16'N/mm
2
inworkin,
stressdesign.
46
usedthehorizontal distance betweenbars of a
groupmaybereducedtotwo-thirdsthe
nominal maximumsizeof the coarseaggregate,
provided that sufficient space is left between
groupsof bars toenable the vibrator to be
immersed.
c) Where there arc two or more rows of bars, the
bursshallhevertically in line and the minimum
verticaldistancebetween the bars shall be
15mrn,two-thirds the nominalmaximumsize
ofaggregateor the maximum size of bars,
whichever is greater.
26.3.3
Maxi/nun,DistanceBetweenBars inTension
Unless the calculation of crack widths shows that a
greaterspacing isacceptable,the followingrules shall
he applied to flexural members in normal internal or
external conditions of exposure.
a)Beams- Thehorizontal distance between
parallelreinforcement bars, or groups, ncarthe
tension face of a beam shall not be greater
than the value given in Table 15 depending on
the amount ofredistributioncarriedout in
analysisandthe characteristic strength of the
reinIorcement.
b)
Slabs
1) Thehorizontaldistancebetweenparallelmain
reinforcementbarsshallnotbemorethanthree
times the effective depth of solid slab or
300IntTIwhicheveris smaller.
2) The horizontal distance between parallel
reinforcementbarsprovidedagainst
shrinkageandtemperatureshall not be more
thanfive times the effectivedepth of a solid
slab or 450 mm whichever is
smaIJer.
26.4 NominalCovertoReinforcement
26.4.1NominalCover
Nominal cover is the design depth of concrete cover
to all steel reinforcements, including links. It is the
dimensionusedindesignand indicatedin thedrawings.
I
tshall benotless than the diameter of the bar.
26.4.2NominalCovertoMeetDurability
Requirement
Minimum values for the nominal cover of normal
weight aggregate concrete which should
beprovided
to all reinforcement, including links
dependingonthe
condition of exposure described in
8.2.3shall be as
given in Table 16.
26.4.2.1 However for alongitudinalreinforcing
bar in a column nominal cover shall in
anycase not
be less than 40 mm, or less than thediameterof
such bar. In the case
ofcolumnsofminimum
dimensionof 200 mmor under,whosereinforcing bars
do not exceed 12mm, a nominal cover of 25 mm
may
be used.
26.4.2.2 For footingsminimumcover shall be 50 mm.
26.4.3 Nominal Cover to
MeetSpecified Periodof
FireRe..sistance
Minimumvalues of nominal cover of normal-weight
aggregateconcrete to be provided to all reinforcement
includinglinks to meetspecifiedperiod
offire
resistance shall
begiven in Table 16A.
26.5RequirementsofReinforcement
for
StructuralMembers
26.5.1Beams
26.5.1.1Tensionreinforcement
a)Minimumreinforcement-Theminimumareaof
tensionreinforcementshall be not less than that
....
Table 15ClearDistance BetweenBars
tCtause26.3.3)
f).PercentageRedistribution to or fromSectionConsidered
-10 -15 0 +I~ +30
Clear Distance BetweenBan
NIJnln
2
nun mm mm mm mm
2~() 215 260 300 300300
415 12~ 15~ 180 210 235
500 105 130 150 17S 195
N()TE - Thespacingsgiven inthetablearenotapplicabletomemberssubjectedtoparticularlyagressiveenvironmentsunlessinthe
calculationof'the momentofresistance,I.,hasbeenlimitedto300N/mm
2
inlimitstartdesianondaliilimitedto16'N/mm
2
inworkin,
stressdesign.
46
IS456:2000
Table16NominalCovertoMeetDurabilityRequirements
iClause26.4.2)
Exposure
Mild
Moderate
Severe
Verysevere
Extreme
NominalCencreteCoverInmm not
LeuThan
20
30
45
50
75
NOTES
1 For main reinforcementup to 121nnldiameterbarfornliJdexposure the nominalcover maybereducedby5mm.
2Unless specifiedotherwise. actual concretecover shouldnotdeviate from therequirednominalcoverby+I0 mm
o
3 For exposurecondition'severe'and 'very severe'.reductionof5mmInf:lYhemade.whereconcretegradeisM35and above.
Table16A
NominalCovertoMeetSpecifiedPeriodofFireResistance
iClauses21.4and26.4.3 andFig.I)
NominalCover
20 20 20 20 20 20 40
20 20 20 20 20 20 40
20 20 25 20~ 20 40
~ 30 .:u 25 4S J.1 40
60 ~ 45 .ll 5S 45 40
70 50 55 45 65 55 40
NOTES
1 Thenominalcoverslivenrelate specificallyto the minimummemberdimensionsgiven in Fig. I.
2Casesthatlie belowtbeboldlinerequireattentiontotheadditionalmeasuresnecessaryto reducetherisksof spallingisee21.3.1).
Fire
Resis
tance
h
o.s
I
1.5
2
3
4
Simply
supported
mm
...
Beams
Continuous
mm
Simply
supported
nun
Slabs
Continuous
rnrn
Simply
supported
mm
Ribs
Continuous
min
Columns
mm
givenbythefollowing:~=0.85
bd fy
where
A.=minimum area of tensionreinforcement,
b=breadthof beamor the breadthoftheweb
of 'f-beam.
d=effective depth, and
f,=characteristicstrengthofreinforcementin
N/mm
2
•
b)
Maximumreinfo~eme",- Themaximumareaof
tensionreinforcementshallnotexceed0.04bD.
26.5.1.2Compressionreinforcement
Themaximumarea ofcompressionreinforcement
shall notexceed 0.04bD.Compressionreinforcement
in beams shall beenclosed bystirrupsfor effective
lateral restraint. Thearrangementof stirrups shallbe
as specified in26.5.3.2.
26.5.1.3Sidefacereinforcement
Wherethedepthofthe webina beamexceeds750mm,
sidefacereinforcementshall
beprovidedalongthe two
faces.The totalareaof suchreinforcementshall benot
less than 0.1percentofthe webareaandshallbe
distributedequallyon two faces at aspacing
notexceeding300
111mor webthicknesswhicheveris
less.
26.5.1.4Transversereinforcementin beamsfor shear
andtorsion
Thetransversereinforcementinbeamsshall betaken
around the outer-mosttension and compressionbars.
"InT-beamsandf-beams,suchreinforcementshallpass
aroundlongitudinalbarslocatedclose to theouter face
of the
flange.
26.5.1.5Maximumspacingofshearreinforcement
Themaximumspacingofshearreinforcement
measuredalongtheaxisofthemembershallnotexceed
0.75 dfor vertical stirrups anddfor inclined stirrups
at45'\wheredistheeffective depth of the section
47
Table16NominalCovertoMeetDurabilityRequirements
iClause26.4.2)
Exposure
Mild
Moderate
Severe
Verysevere
Extreme
NominalCencreteCoverInmm not
LeuThan
20
30
45
50
75
NOTES
1 For main reinforcementup to 121nnldiameterbarfornliJdexposure the nominalcover maybereducedby5mm.
2Unless specifiedotherwise. actual concretecover shouldnotdeviate from therequirednominalcoverby+I0 mm
o
3 For exposurecondition'severe'and 'very severe'.reductionof5mmInf:lYhemade.whereconcretegradeisM35and above.
Table16A
NominalCovertoMeetSpecifiedPeriodofFireResistance
iClauses21.4and26.4.3 andFig.I)
NominalCover
20 20 20 20 20 20 40
20 20 20 20 20 20 40
20 20 25 20~ 20 40
~ 30 .:u 25 4S J.1 40
60 ~ 45 .ll 5S 45 40
70 50 55 45 65 55 40
NOTES
1 Thenominalcoverslivenrelate specificallyto the minimummemberdimensionsgiven in Fig. I.
2Casesthatlie belowtbeboldlinerequireattentiontotheadditionalmeasuresnecessaryto reducetherisksof spallingisee21.3.1).
Fire
Resis
tance
h
o.s
I
1.5
2
3
4
Simply
supported
mm
...
Beams
Continuous
mm
Simply
supported
nun
Slabs
Continuous
rnrn
Simply
supported
mm
Ribs
Continuous
min
Columns
mm
givenbythefollowing:~=0.85
bd fy
where
A.=minimum area of tensionreinforcement,
b=breadthof beamor the breadthoftheweb
of 'f-beam.
d=effective depth, and
f,=characteristicstrengthofreinforcementin
N/mm
2
•
b)
Maximumreinfo~eme",- Themaximumareaof
tensionreinforcementshallnotexceed0.04bD.
26.5.1.2Compressionreinforcement
Themaximumarea ofcompressionreinforcement
shall notexceed 0.04bD.Compressionreinforcement
in beams shall beenclosed bystirrupsfor effective
lateral restraint. Thearrangementof stirrups shallbe
as specified in26.5.3.2.
26.5.1.3Sidefacereinforcement
Wherethedepthofthe webina beamexceeds750mm,
sidefacereinforcementshall
beprovidedalongthe two
faces.The totalareaof suchreinforcementshall benot
less than 0.1percentofthe webareaandshallbe
distributedequallyon two faces at aspacing
notexceeding300
111mor webthicknesswhicheveris
less.
26.5.1.4Transversereinforcementin beamsfor shear
andtorsion
Thetransversereinforcementinbeamsshall betaken
around the outer-mosttension and compressionbars.
"InT-beamsandf-beams,suchreinforcementshallpass
aroundlongitudinalbarslocatedclose to theouter face
of the
flange.
26.5.1.5Maximumspacingofshearreinforcement
Themaximumspacingofshearreinforcement
measuredalongtheaxisofthemembershallnotexceed
0.75 dfor vertical stirrups anddfor inclined stirrups
at45'\wheredistheeffective depth of the section
47
15456:2000
underconsideration.1ftnocaseshall thespacinl
exceed300mm.
26.5.1.6Minim"".,ltearrein/orreNnt
Minimumshearreinforcementintheformofstinups
shallbeprovidedsuchthat:
where
AI.• totalcross-sectionalareaof stirruplop
effectiveinshear.
'.• stirrupSPacinlalonlthoIeft8thofthe
member.
b =-breadthofthebeam orbreadthofthe
webofftanledbeam.and
I.,•characteristicItreDltbof thestirrup
reinforcementinN/mm
2
whichshallnot
betakenpaterdian415N/mm
2
•
Wherethemaximumshearstresscalculated illelsthan
halfthepermissiblevalue and inmembenof minor
structuralimportancesuchulintels.thisprovision
neednotbecompliedwith.
Z6.5.1.7Distributiolloftorsto«Teinfol'C~nielll
When a member isdesilnedfortonion(,~,41 or
8-6)tonionreinforcementshallbeprovidedubelow:
a)Thetransversereinforcementfor tonion sball
berectanplarclosedstirrupsplacedperpen
dicularto theWSofthemember.Thespacinl
ofthestirrup.shall notexceedtheleaJtof
.I.,.I,:"and300mm,whele.I.and,.IR
reapectivelytheshortandlonldimension.of
theltimap.
b)Lonptudinalreinforcementshallbeplaced..
closeasispracticabletothecornenoftbecroa..
sectionandin allcasea,thereshallbeatleat
oneIonJitudinaibarineachcom.ofthetiel.
Whenthecroll-sectionaldimension of the
memberexceeds450mm,additional
longitudinalbars.shallbeprovidedtosatisfythe
requirementl ofminimumreinforcementand
spacinlgivenin26.5.1.3.
26.5.1.8ReinforcementinOanlOSofT-nL-beams
shall satisfytherequirementsin23.1.1(b).Where
tlaDlesareinteuioD,• partofthemain tension
reinforcementshallbedillribuledovertheeffective
flanlewidthor a widthequalto~tonthofthespan.
whichever is smaller. If theeffectiveflanlewidth
exceedsone-tenthofthespan,nominallonaitudinal
reinforcementshall beprovidedintheouterportions
oftheflap.
26.5.2Slab,
Theruleslivenin36.1.2..1andZU.2.2shallapply
toslabsinadditiontothose,twnintheappropriate
clauses.
25.1.11Minimwn"injorceIMnt
ThemildlteelreinforcemeatIIIlithertlli'ectidtlill~tatil
shall notbeloathin0,IS~ftt"'.ro\8lcross
sectional....Ho...tiltWI'Uecanbereducedto
0.12peneIlt~henbiSbstrengthdeformed bars or
weldedwirefabricareused.
26.5.12Mtuimum diGm't~r
ThediameterofreinforciqbanaballbOte~ ODe4(.
eishtofthetotalthicbluof1M.a.b.
26.5.3Col...,.,
26.5.11~ reinforcement
I)Thecross-sectionalareaoflonaitudinal
reinforcement,
shall
benotlessthan0.8pIIIIftl
nor morothan6percent of thearo.'~••.
sectionalareaofthecolumn.
NOTB-"'..of6,...Ninf........may.VoIve
prlCticaidtftlcultielinpladnl-lDIbp8cdD.of~;
hence10..perceMII*I.Neommencled.WhentMn~
thecol_belowhavetobe.......\'fmcinthe
columnuDdereoDli~..peltentaaeofsteellhlll
aUllI,DOlex~4perce•.
b) InanycolumnthatbasaIUJercross-sectional
area than thatrequiredto supporttheload~
theminimumpercenta,eof steelIhallbe
buedupontheareaofconcreterequlNClto
resist the directstressandDotupontheactual
area.
c)Theminimum number ofloqil\kllftalban
providedin•columnIbIIlbefourinrectaDplar
columnsandsixillcircullrcolumns.
d)Thebarsshall not be less than 12 mm in
diameter.
e) Areinforcedconcrete column havinlhelical
reinforcement shall have atleutlixbinof
lonlitudinalreinforcement withinthohelical
reinforcement.
f)Inahelically_fmeedcolumn.thelonptudinal
barsshall beincontactwith thehelical
reinforcementandequidistantarounditsinner
circumference.
s)·Spacinaoflonptudinalbarsmeuuredalonl
theperipheryofthecolumnshallnotexceed
300mm.
h) IncaseofpedeStallin whichtheIORlitudinal
reinforcementisDottakeDinaccountinstrenath
calculations,nominaIlonptudinaireinforcement
notless.than0.15percentof thecross-sectional
area'shallbeprovided.
48
underconsideration.1ftnocaseshall thespacinl
exceed300mm.
26.5.1.6Minim"".,ltearrein/orreNnt
Minimumshearreinforcementintheformofstinups
shallbeprovidedsuchthat:
where
AI.• totalcross-sectionalareaof stirruplop
effectiveinshear.
'.• stirrupSPacinlalonlthoIeft8thofthe
member.
b =-breadthofthebeam orbreadthofthe
webofftanledbeam.and
I.,•characteristicItreDltbof thestirrup
reinforcementinN/mm
2
whichshallnot
betakenpaterdian415N/mm
2
•
Wherethemaximumshearstresscalculated illelsthan
halfthepermissiblevalue and inmembenof minor
structuralimportancesuchulintels.thisprovision
neednotbecompliedwith.
Z6.5.1.7Distributiolloftorsto«Teinfol'C~nielll
When a member isdesilnedfortonion(,~,41 or
8-6)tonionreinforcementshallbeprovidedubelow:
a)Thetransversereinforcementfor tonion sball
berectanplarclosedstirrupsplacedperpen
dicularto theWSofthemember.Thespacinl
ofthestirrup.shall notexceedtheleaJtof
.I.,.I,:"and300mm,whele.I.and,.IR
reapectivelytheshortandlonldimension.of
theltimap.
b)Lonptudinalreinforcementshallbeplaced..
closeasispracticabletothecornenoftbecroa..
sectionandin allcasea,thereshallbeatleat
oneIonJitudinaibarineachcom.ofthetiel.
Whenthecroll-sectionaldimension of the
memberexceeds450mm,additional
longitudinalbars.shallbeprovidedtosatisfythe
requirementl ofminimumreinforcementand
spacinlgivenin26.5.1.3.
26.5.1.8ReinforcementinOanlOSofT-nL-beams
shall satisfytherequirementsin23.1.1(b).Where
tlaDlesareinteuioD,• partofthemain tension
reinforcementshallbedillribuledovertheeffective
flanlewidthor a widthequalto~tonthofthespan.
whichever is smaller. If theeffectiveflanlewidth
exceedsone-tenthofthespan,nominallonaitudinal
reinforcementshall beprovidedintheouterportions
oftheflap.
26.5.2Slab,
Theruleslivenin36.1.2..1andZU.2.2shallapply
toslabsinadditiontothose,twnintheappropriate
clauses.
25.1.11Minimwn"injorceIMnt
ThemildlteelreinforcemeatIIIlithertlli'ectidtlill~tatil
shall notbeloathin0,IS~ftt"'.ro\8lcross
sectional....Ho...tiltWI'Uecanbereducedto
0.12peneIlt~henbiSbstrengthdeformed bars or
weldedwirefabricareused.
26.5.12Mtuimum diGm't~r
ThediameterofreinforciqbanaballbOte~ ODe4(.
eishtofthetotalthicbluof1M.a.b.
26.5.3Col...,.,
26.5.11~ reinforcement
I)Thecross-sectionalareaoflonaitudinal
reinforcement,
shall
benotlessthan0.8pIIIIftl
nor morothan6percent of thearo.'~••.
sectionalareaofthecolumn.
NOTB-"'..of6,...Ninf........may.VoIve
prlCticaidtftlcultielinpladnl-lDIbp8cdD.of~;
hence10..perceMII*I.Neommencled.WhentMn~
thecol_belowhavetobe.......\'fmcinthe
columnuDdereoDli~..peltentaaeofsteellhlll
aUllI,DOlex~4perce•.
b) InanycolumnthatbasaIUJercross-sectional
area than thatrequiredto supporttheload~
theminimumpercenta,eof steelIhallbe
buedupontheareaofconcreterequlNClto
resist the directstressandDotupontheactual
area.
c)Theminimum number ofloqil\kllftalban
providedin•columnIbIIlbefourinrectaDplar
columnsandsixillcircullrcolumns.
d)Thebarsshall not be less than 12 mm in
diameter.
e) Areinforcedconcrete column havinlhelical
reinforcement shall have atleutlixbinof
lonlitudinalreinforcement withinthohelical
reinforcement.
f)Inahelically_fmeedcolumn.thelonptudinal
barsshall beincontactwith thehelical
reinforcementandequidistantarounditsinner
circumference.
s)·Spacinaoflonptudinalbarsmeuuredalonl
theperipheryofthecolumnshallnotexceed
300mm.
h) IncaseofpedeStallin whichtheIORlitudinal
reinforcementisDottakeDinaccountinstrenath
calculations,nominaIlonptudinaireinforcement
notless.than0.15percentof thecross-sectional
area'shallbeprovided.
48
NOTE-Pedestalisacompreuionmember.theeffective
lenlthofwhichdoesnotexceedthreetime.theleastlateral
dimension.
26.5.3.2Transversereinforcement
a)General-Areinforcedconcretecompression
membershallhavetransverseorhelical
reinforcementsodisposedthat every
longitu
dinal bar nearest to the compression face
has effective lateral support againstbuckling
subjecttoprovisionsin(b). The
effectivelateral
supportisgivenbytransversereinforcement
either in the fonn of circular ringscapableof
takingupcircumferentialtensionor
by
polygonallinks(lateralties)withinternalangles
notexceeding13.5
0
•
Theendsof thetransverse
reinforcementshall be properly anchored
[see
26.2.2.4(b)].
b)Arrangementoftransversereinforcement
1) If thelongitudinalbars arenotspacedmore
than 75 mm on either side. transverse
reinforcementneedonlyto goroundcorner
andalternatebars for the purpose of
providingeffectivelateralsupports
(setFig. 8).
2) If thelongitudinalbars spacedat adistance
of notexceeding48 times thediameterof
the
tie are effectivelytiedin twodirections.
additionallongitudinalbarsinbetweenthese
barsneedtobetiedinonedirection byopen
ties
(seeFig. 9). '
3) Where thelongitudinalreinforcingbars in
acompression
memberare placedin more
thanone
row,effectivelateral supporttothe
longitudinalbars
inthe innerrows maybe
assumedto havebeenprovidedif:
i)transversereinforcementis providedfor
theouter-mostrow in accordancewith
26.5.3.2,and
ii)no bar of the inner row is closer to the
nearest compression face than three
times thediameterof thelargestbar in
the innerrow
(seeFig.10).
4) Where the longitudinal bars in a com
pressionmember are grouped (not in
contact)andeach
groupadequately
tiedwith
transversereinforcementinaccordancewith
26.5.3.2,thetransversereinforcementforthe
compressionmember as a wholemaybe
providedon the assumptionthateachgroup
is a singlelongitudinalbar for purposeof
determining the pitch and diameter of the
transversereinforcementin accordancewith
26.5.3.2.Thediameterof such transverse
2116BIS/07-8 49
IS456:2000
reinforcementneed not. however,exceed
20
mm
(seeFig.11).
c)Pitchanddiameterof laura;tits
J)Pitch-Thepitch oftransversereinforce
mentshall
benotmorethan the leastof the
followingdistances:
i)The least lateral dimension of the
compression
members;
ii)Sixteentimesthesmallestdiameterof
the
longitudinalreinforcementbartobe
tied:and
iii) 300mm.
2)Diameter-Thediameterof thepolygonal
linksorlateraltiesshallbenotlessthanone
fourth of thediameterof thelargest
longitudinalbar. and in no case less than
16mm.
d)Helical
reinforcement
1)Pitch-Helicalreinforcementshall beof
regular
formationwiththe
turnsof the helix
spacedevenlyanditsendsshallbeanchored
properlybyprovidingone and ahalf extra
turnsof the spiralbar.Whereanincreased
load on
thecolumnon thestrengthof the
helicalreinforcementisallowedfor,thepitch
ofhelicalturnsshallbenotmorethan
75mm,
normorethanone-sixthof thecorediameter
of the
column.norless than
2.5mm,norless
thanthreetimesthediameterof thesteelbar
forming the helix.
.Inother cases, the
requirementsof
26.5.3.2shallbecomplied
with.
2) The diameter of thehelicalreinforcement
shall
beinaccordancewith
26.5.3.2(c) (2).
26.5.3.3Incolumnswherelongitudinalbarsareoffset
at a
splice,theslopeoftheinclinedportionof the bar
with the axis of the
columnshallnot exceed1in 6.
and the portionsofthebaraboveandbelowtheoffset
shall beparalleltotheaxis of thecolumn.Adequate
horizontalsupportat the offsetbendsshallbetreated
as a matterof
design.and shallbeprovidedbymetal
ties,
spirals.orpartsof thefloorconstruction.Metal
ties or
spiralssodesignedshallbeplaced near (not
morethaneight-bardiameters
from)thepointofbend.
The
horizontalthrusttoberesistedshall beassumed
as one and half
timesthehorizontalcomponents
of
thenominalstress in theinclinedportionof the bar.
Offsetbarsshallbebentbeforetheyare placedin the
forms,Wherecolumnfacesareoffset75mmormore,
splicesofverticalbarsadjacentto theoffsetfaceshall
be made
byseparatedowelsoverlappedasspecified
in
26.2.5.1.
lenlthofwhichdoesnotexceedthreetime.theleastlateral
dimension.
26.5.3.2Transversereinforcement
a)General-Areinforcedconcretecompression
membershallhavetransverseorhelical
reinforcementsodisposedthat every
longitu
dinal bar nearest to the compression face
has effective lateral support againstbuckling
subjecttoprovisionsin(b). The
effectivelateral
supportisgivenbytransversereinforcement
either in the fonn of circular ringscapableof
takingupcircumferentialtensionor
by
polygonallinks(lateralties)withinternalangles
notexceeding13.5
0
•
Theendsof thetransverse
reinforcementshall be properly anchored
[see
26.2.2.4(b)].
b)Arrangementoftransversereinforcement
1) If thelongitudinalbars arenotspacedmore
than 75 mm on either side. transverse
reinforcementneedonlyto goroundcorner
andalternatebars for the purpose of
providingeffectivelateralsupports
(setFig. 8).
2) If thelongitudinalbars spacedat adistance
of notexceeding48 times thediameterof
the
tie are effectivelytiedin twodirections.
additionallongitudinalbarsinbetweenthese
barsneedtobetiedinonedirection byopen
ties
(seeFig. 9). '
3) Where thelongitudinalreinforcingbars in
acompression
memberare placedin more
thanone
row,effectivelateral supporttothe
longitudinalbars
inthe innerrows maybe
assumedto havebeenprovidedif:
i)transversereinforcementis providedfor
theouter-mostrow in accordancewith
26.5.3.2,and
ii)no bar of the inner row is closer to the
nearest compression face than three
times thediameterof thelargestbar in
the innerrow
(seeFig.10).
4) Where the longitudinal bars in a com
pressionmember are grouped (not in
contact)andeach
groupadequately
tiedwith
transversereinforcementinaccordancewith
26.5.3.2,thetransversereinforcementforthe
compressionmember as a wholemaybe
providedon the assumptionthateachgroup
is a singlelongitudinalbar for purposeof
determining the pitch and diameter of the
transversereinforcementin accordancewith
26.5.3.2.Thediameterof such transverse
2116BIS/07-8 49
IS456:2000
reinforcementneed not. however,exceed
20
mm
(seeFig.11).
c)Pitchanddiameterof laura;tits
J)Pitch-Thepitch oftransversereinforce
mentshall
benotmorethan the leastof the
followingdistances:
i)The least lateral dimension of the
compression
members;
ii)Sixteentimesthesmallestdiameterof
the
longitudinalreinforcementbartobe
tied:and
iii) 300mm.
2)Diameter-Thediameterof thepolygonal
linksorlateraltiesshallbenotlessthanone
fourth of thediameterof thelargest
longitudinalbar. and in no case less than
16mm.
d)Helical
reinforcement
1)Pitch-Helicalreinforcementshall beof
regular
formationwiththe
turnsof the helix
spacedevenlyanditsendsshallbeanchored
properlybyprovidingone and ahalf extra
turnsof the spiralbar.Whereanincreased
load on
thecolumnon thestrengthof the
helicalreinforcementisallowedfor,thepitch
ofhelicalturnsshallbenotmorethan
75mm,
normorethanone-sixthof thecorediameter
of the
column.norless than
2.5mm,norless
thanthreetimesthediameterof thesteelbar
forming the helix.
.Inother cases, the
requirementsof
26.5.3.2shallbecomplied
with.
2) The diameter of thehelicalreinforcement
shall
beinaccordancewith
26.5.3.2(c) (2).
26.5.3.3Incolumnswherelongitudinalbarsareoffset
at a
splice,theslopeoftheinclinedportionof the bar
with the axis of the
columnshallnot exceed1in 6.
and the portionsofthebaraboveandbelowtheoffset
shall beparalleltotheaxis of thecolumn.Adequate
horizontalsupportat the offsetbendsshallbetreated
as a matterof
design.and shallbeprovidedbymetal
ties,
spirals.orpartsof thefloorconstruction.Metal
ties or
spiralssodesignedshallbeplaced near (not
morethaneight-bardiameters
from)thepointofbend.
The
horizontalthrusttoberesistedshall beassumed
as one and half
timesthehorizontalcomponents
of
thenominalstress in theinclinedportionof the bar.
Offsetbarsshallbebentbeforetheyare placedin the
forms,Wherecolumnfacesareoffset75mmormore,
splicesofverticalbarsadjacentto theoffsetfaceshall
be made
byseparatedowelsoverlappedasspecified
in
26.2.5.1.
IS456: 2000
27EXPANSIONJOINTS
27.1
Structuresin whichmarkedchangesin plan
dimensionstakeplaceabruptlyshallbeprovidedwith
expansiononjointsatthesectionwheresuchchanges
occur.Expansionjointsshallbesoprovidedthatthe
necessary movement occurs with a minimum
resistanceatthejoint.Thestructuresadjacentto the
joint
shouldpreferablybesupportedonseparate
columnsorwallsbut notnecessarilyonseparate
foundations.Reinforcementshallnotextendacross
anexpansionjointandthebreakbetweenthesections
shall becomplete.'
27.2Thedetailsastothelenithofastructurewhere
expansionjointshavetobeprovidedcanbedetennined
aftertakingintoconsiderationvariousfactors.suchas
temperature,exposuretoweather.thetimeandseason
ofthelayingoftheconcrete.etc.Normallystructures
exceeding45m inlenitharedesignedwithone or
moreexpansionjoints.Howeverinviewofthelarge
numberoffactorsinvolvedindecidingthelocation.
spacingandnatureofexpansionjoints.theprovision
ofexpansionjoint inreinforcedcementconcrete
structures
should
beleft to thediscretionof the
designer.IS3414givesthedesignconsiderations,
wJtichneedtobeexaminedandprovidedfor.
AlldimensionsInmillimetres. AlldimensionsInmlllimetres.
Flo.8 Flo.9
'ND'VIDUALGROUPS
TRANSVERSEREINFORCEMENT
...
'"1\
Alldimensionsinmillimetres.
FIG.10
FrG.11
50
27EXPANSIONJOINTS
27.1
Structuresin whichmarkedchangesin plan
dimensionstakeplaceabruptlyshallbeprovidedwith
expansiononjointsatthesectionwheresuchchanges
occur.Expansionjointsshallbesoprovidedthatthe
necessary movement occurs with a minimum
resistanceatthejoint.Thestructuresadjacentto the
joint
shouldpreferablybesupportedonseparate
columnsorwallsbut notnecessarilyonseparate
foundations.Reinforcementshallnotextendacross
anexpansionjointandthebreakbetweenthesections
shall becomplete.'
27.2Thedetailsastothelenithofastructurewhere
expansionjointshavetobeprovidedcanbedetennined
aftertakingintoconsiderationvariousfactors.suchas
temperature,exposuretoweather.thetimeandseason
ofthelayingoftheconcrete.etc.Normallystructures
exceeding45m inlenitharedesignedwithone or
moreexpansionjoints.Howeverinviewofthelarge
numberoffactorsinvolvedindecidingthelocation.
spacingandnatureofexpansionjoints.theprovision
ofexpansionjoint inreinforcedcementconcrete
structures
should
beleft to thediscretionof the
designer.IS3414givesthedesignconsiderations,
wJtichneedtobeexaminedandprovidedfor.
AlldimensionsInmillimetres. AlldimensionsInmlllimetres.
Flo.8 Flo.9
'ND'VIDUALGROUPS
TRANSVERSEREINFORCEMENT
...
'"1\
Alldimensionsinmillimetres.
FIG.10
FrG.11
50
IS456:2000
SECTION4 SPECIALDESIGNREQUIREMENTSFORSTRUCTURAL
MEMBERSAND.SYSTEMS
29.2Lever Arm
29DEEPBEAMS
where/ is theeffectivespantakenascentre to centre
distancebetweensupportsor1.15timestheclearspan,
whicheverissmaller,andDis theoveralldepth.
19.3Reinforcement
28.2.4Resistanceto Applied HorizontalForce
Additional reinforcement connected to the supported
member should be provided to transmit this force in
itsentirety.
/
when -<1
D
I
when 1
S-~2.5
D
I
when -<1
l)
z=0.5I
or
z=0.2(I+1.5D)
or
z=0.61
b) For continuous beams.
29.3.1PositiveReinforcement
The tensilereinforcementrequiredto resistpositive
bending moment inanyspanofadeepbeam shall:
a) extend withoutcurtailm- ..~r1tbetween supports;
b)be embedded beyond thefaceofeach support,
so that at the face of the support it shall have a
development
lengthnotless than 0.8LtJ;where
L,jisthe developmentlength(see26.2.1).for
the design stressin thereinforcement;and
The lever armzfor a deep beam shall be detemineda~
below:
a) For
simplysupported beauts:
I
z=0.2(I+2D) whenI~-~2
D
29.1General
a) A beamshallbedeemedtobeadeepbeam when
the ratio of effective span to overall depth.~
is less than:
1) 2.0 for a simply supported beam; and
2) 2.5 for a continuous beam.
b) A deep beam complying with the requirements
of29.2and29.3shallbedeemed to satisfythe
provisions for shear.
18.1.3ShearReinforcement
Shear reinforcement should be provided in the form
of horizontal links distributed in the upper two-third
of theeffectivedepth of root of thecorbel;this
reinforcement should benotless than one-halfofthe
areaof the main tension reinforcement and shouldbe
adequately anchored.
28.2Design
28.2.1SimplifyingAssumptions
Theconcrete"andreinforcementmay be assumedto
act as elements of a simple strut-and-tie system, with
the following guidelines:
a) The magnitude of the
resistanceprovided to
horizontalforceshouldbe notless thanone-half
ofthedesignverticalload on thecorbel
(seealso28.2.4).
b) Compatibility of strains between the strut-and..
tie at the corbel foot should be ensured.
It should be noted that the horizontal link requirement
described in28.2.3will ensure satisfactory service
ability performance.
28.2.2ReinforcementAnchorag«
At thefrontfaceofthecorbel,thereinforcementshould
be anchored either
by:
a)
weldingtoatransversebar ofequalstrength
in this case the hearing area of the load should
stopshortof the faceofthesupportbyadistance
equal to the cover of the tie reinforcement, or
b)
bendingbuck the bars toform aloop-inthis
casethebearingareaof the loadshould
notprojectbeyond thestraightportionof
thebarsformingthemaintensionreinforcement,
28.1General
28CONCRETECORBELS
Acorbel is a short cantileverprojectionwhichsupports
a load bearing member and where:
a) . the distance
a
v
between the line of the reaction
to the supported load and the root of the corbel
is less than
d(the effective depth of the root of
the corbel); and
b) thedepthatthe outeredgeofthecontactarea
of the supported load is not less than one-half
of the depth at the root of the corbel.
The depth
ofthecorbelat the face of the support is
determined inaccordance with 40.5.1.
51
SECTION4 SPECIALDESIGNREQUIREMENTSFORSTRUCTURAL
MEMBERSAND.SYSTEMS
29.2Lever Arm
29DEEPBEAMS
where/ is theeffectivespantakenascentre to centre
distancebetweensupportsor1.15timestheclearspan,
whicheverissmaller,andDis theoveralldepth.
19.3Reinforcement
28.2.4Resistanceto Applied HorizontalForce
Additional reinforcement connected to the supported
member should be provided to transmit this force in
itsentirety.
/
when -<1
D
I
when 1
S-~2.5
D
I
when -<1
l)
z=0.5I
or
z=0.2(I+1.5D)
or
z=0.61
b) For continuous beams.
29.3.1PositiveReinforcement
The tensilereinforcementrequiredto resistpositive
bending moment inanyspanofadeepbeam shall:
a) extend withoutcurtailm- ..~r1tbetween supports;
b)be embedded beyond thefaceofeach support,
so that at the face of the support it shall have a
development
lengthnotless than 0.8LtJ;where
L,jisthe developmentlength(see26.2.1).for
the design stressin thereinforcement;and
The lever armzfor a deep beam shall be detemineda~
below:
a) For
simplysupported beauts:
I
z=0.2(I+2D) whenI~-~2
D
29.1General
a) A beamshallbedeemedtobeadeepbeam when
the ratio of effective span to overall depth.~
is less than:
1) 2.0 for a simply supported beam; and
2) 2.5 for a continuous beam.
b) A deep beam complying with the requirements
of29.2and29.3shallbedeemed to satisfythe
provisions for shear.
18.1.3ShearReinforcement
Shear reinforcement should be provided in the form
of horizontal links distributed in the upper two-third
of theeffectivedepth of root of thecorbel;this
reinforcement should benotless than one-halfofthe
areaof the main tension reinforcement and shouldbe
adequately anchored.
28.2Design
28.2.1SimplifyingAssumptions
Theconcrete"andreinforcementmay be assumedto
act as elements of a simple strut-and-tie system, with
the following guidelines:
a) The magnitude of the
resistanceprovided to
horizontalforceshouldbe notless thanone-half
ofthedesignverticalload on thecorbel
(seealso28.2.4).
b) Compatibility of strains between the strut-and..
tie at the corbel foot should be ensured.
It should be noted that the horizontal link requirement
described in28.2.3will ensure satisfactory service
ability performance.
28.2.2ReinforcementAnchorag«
At thefrontfaceofthecorbel,thereinforcementshould
be anchored either
by:
a)
weldingtoatransversebar ofequalstrength
in this case the hearing area of the load should
stopshortof the faceofthesupportbyadistance
equal to the cover of the tie reinforcement, or
b)
bendingbuck the bars toform aloop-inthis
casethebearingareaof the loadshould
notprojectbeyond thestraightportionof
thebarsformingthemaintensionreinforcement,
28.1General
28CONCRETECORBELS
Acorbel is a short cantileverprojectionwhichsupports
a load bearing member and where:
a) . the distance
a
v
between the line of the reaction
to the supported load and the root of the corbel
is less than
d(the effective depth of the root of
the corbel); and
b) thedepthatthe outeredgeofthecontactarea
of the supported load is not less than one-half
of the depth at the root of the corbel.
The depth
ofthecorbelat the face of the support is
determined inaccordance with 40.5.1.
51
IS456:2000
c) be placed within a zone of depth equal to
0.25D-0.0'Iadjacentto thetensionfaceof
the beamwhereDis theoveralldepthandIis
theeffectivespan.
29.3.2Negative Reinforc,ment
a)Terminationofreinforcement-Por tensile
reinforcementrequired
toresist negative
bendingmomentoverasupportofa
deepbeam:
1)Itshallbepermissibletotenninatenotmore
thanhalf of thereinforcementat adistance
ofO.~Dfromthefaceof thesupportwhere
Dis asdefinedin29.2;and
2) Theremaindershall extend
overthe full
span.
b)Distribution-Whenratio of clear span to
overalldepthis in the range 1.0to
2.5.tensile
reinforcementover a supportof adeepbeam
shallbeplacedin twozonescomprising:'
1)azoneofdepth0.2D.adjacenttothetension
face.whichshallcontainaproportionofthe
•..tensionsteelgivenby
O.S(~-o.s)
where
I=clearspan.and
D=overalldepth.
2) azonemeasuring0.3Don eitherside of
the
mid-depthof thebeam,which
shall
containtheremainderof thetensionsteel,
evenlydistributed.
Forspantodepth
ratioslessthanunity.the
steel shall be evenlydistributedover a
depthof 0.8
Dmeasuredfromthetension
face.
29.3.3VerticalReinforctmt1l1
Ifforcesareappliedtoadeepbeaminsuchawaythat
hangingactionisrequired.barsorsuspensionstil'NPS
shallbeprovidedtocarryalltheforcesconcerned.
19.3.4SideFaceReinforcement
Side facereinforcementshall complywithrequire..
mentsofminimumreinforcementof walls(ste32.4).
30RIBBED.HOLLOWBLOCKORVQIDEDSLAB
30.1General
This coversthe slabsconstructedinoneof theways
describedbelow:
a) As aaeriesofconcreteribswithtoPPinlcaston
formswhichmayberemovedaftertheconcreto
hasset;
b) As a seriesofconcrete.ribsbetweenprecast
blocks which remain part of the completed
ItNcture;thetop oftheribsmaybeconnected
byatoPpinlofconcreteofthesamestrenathas
thatusedin theribs;and
c) With a continuous top and bottom face but
containingvoids ofrectangular,oval or
other
shape.
30.2
AnalysisorStnacture
The moments and forcesdueto desian loads on
continuousslabsmaybeobtainedbythemethodsliven
in
Section3for solidslabs.Alternatively,theslaba
may
bedesignedas a seriesofsimplysupportedspans
providedtheyarenotexposedtoweatherorcorrosive
conditions;widecracksmaydevelopatthesupports
and theengineershall satisfyhimselfthat thesewill
not impair finishes or lead to corrosion of the
reinforcement.
30.3Shear
Where hollow blocks are used, for the purpose
of calculating shear stress. the rib width may be
increasedto takeaccountof thewanthicknessof the
blockononesideoftherib;withnarrowprecastunits.
thewidthof thejointingmortarorconcretemay be
included.
30.4Deflection
The
recommendationsfordeflectioninrespectofsolid
slabsmay
beappliedtoribbed.hollowblockorvoided
construction.Thespantoeffectivedepthratiosliven
in23.2foraflangedbeamareapplicablebut when
calculatingthefinalreductionfactorfor webwidth.
the ribwidthforhollowblockslabsmaybeassumed
toincludethewallsof theblockson bothsidesof the
rib. For
voidedslabsand slabsconstructedof boxor
I-sectionunits.aneffectiveribwidthshall
becalculated
assuminsallmaterialbelow theupperflangeofthe
unitto
beconcentratedin areetanaularrib hlvins the
same
cross-sectionalareaanddepth.
30.5Sizeand Poeltlonof Rib•.
In-situribsshallbenot less than65mmwide.They
shallbespacedatcentresnot greaterthan1.~mapart
and their
depth.excludinganytopping,shall
benot
morethanfourtimestheirwidth.Generallyribsshall
beformedalonseachedgeparallelto the spanof one
wayslabs. Whentheedgeisbuiltintoa wallor rests
ona
beam,a ribat leastas wideas thebearingshallbe
fonned
alonstheed,e.
30.6 HollowBlocksandFormen
Blocksandfonnersmaybe ofanysuitablematerial.
Hollowclaytilesfor the filler type shallconformto
IS39~1 (PartI).Whenrequiredtocontributeto the
c) be placed within a zone of depth equal to
0.25D-0.0'Iadjacentto thetensionfaceof
the beamwhereDis theoveralldepthandIis
theeffectivespan.
29.3.2Negative Reinforc,ment
a)Terminationofreinforcement-Por tensile
reinforcementrequired
toresist negative
bendingmomentoverasupportofa
deepbeam:
1)Itshallbepermissibletotenninatenotmore
thanhalf of thereinforcementat adistance
ofO.~Dfromthefaceof thesupportwhere
Dis asdefinedin29.2;and
2) Theremaindershall extend
overthe full
span.
b)Distribution-Whenratio of clear span to
overalldepthis in the range 1.0to
2.5.tensile
reinforcementover a supportof adeepbeam
shallbeplacedin twozonescomprising:'
1)azoneofdepth0.2D.adjacenttothetension
face.whichshallcontainaproportionofthe
•..tensionsteelgivenby
O.S(~-o.s)
where
I=clearspan.and
D=overalldepth.
2) azonemeasuring0.3Don eitherside of
the
mid-depthof thebeam,which
shall
containtheremainderof thetensionsteel,
evenlydistributed.
Forspantodepth
ratioslessthanunity.the
steel shall be evenlydistributedover a
depthof 0.8
Dmeasuredfromthetension
face.
29.3.3VerticalReinforctmt1l1
Ifforcesareappliedtoadeepbeaminsuchawaythat
hangingactionisrequired.barsorsuspensionstil'NPS
shallbeprovidedtocarryalltheforcesconcerned.
19.3.4SideFaceReinforcement
Side facereinforcementshall complywithrequire..
mentsofminimumreinforcementof walls(ste32.4).
30RIBBED.HOLLOWBLOCKORVQIDEDSLAB
30.1General
This coversthe slabsconstructedinoneof theways
describedbelow:
a) As aaeriesofconcreteribswithtoPPinlcaston
formswhichmayberemovedaftertheconcreto
hasset;
b) As a seriesofconcrete.ribsbetweenprecast
blocks which remain part of the completed
ItNcture;thetop oftheribsmaybeconnected
byatoPpinlofconcreteofthesamestrenathas
thatusedin theribs;and
c) With a continuous top and bottom face but
containingvoids ofrectangular,oval or
other
shape.
30.2
AnalysisorStnacture
The moments and forcesdueto desian loads on
continuousslabsmaybeobtainedbythemethodsliven
in
Section3for solidslabs.Alternatively,theslaba
may
bedesignedas a seriesofsimplysupportedspans
providedtheyarenotexposedtoweatherorcorrosive
conditions;widecracksmaydevelopatthesupports
and theengineershall satisfyhimselfthat thesewill
not impair finishes or lead to corrosion of the
reinforcement.
30.3Shear
Where hollow blocks are used, for the purpose
of calculating shear stress. the rib width may be
increasedto takeaccountof thewanthicknessof the
blockononesideoftherib;withnarrowprecastunits.
thewidthof thejointingmortarorconcretemay be
included.
30.4Deflection
The
recommendationsfordeflectioninrespectofsolid
slabsmay
beappliedtoribbed.hollowblockorvoided
construction.Thespantoeffectivedepthratiosliven
in23.2foraflangedbeamareapplicablebut when
calculatingthefinalreductionfactorfor webwidth.
the ribwidthforhollowblockslabsmaybeassumed
toincludethewallsof theblockson bothsidesof the
rib. For
voidedslabsand slabsconstructedof boxor
I-sectionunits.aneffectiveribwidthshall
becalculated
assuminsallmaterialbelow theupperflangeofthe
unitto
beconcentratedin areetanaularrib hlvins the
same
cross-sectionalareaanddepth.
30.5Sizeand Poeltlonof Rib•.
In-situribsshallbenot less than65mmwide.They
shallbespacedatcentresnot greaterthan1.~mapart
and their
depth.excludinganytopping,shall
benot
morethanfourtimestheirwidth.Generallyribsshall
beformedalonseachedgeparallelto the spanof one
wayslabs. Whentheedgeisbuiltintoa wallor rests
ona
beam,a ribat leastas wideas thebearingshallbe
fonned
alonstheed,e.
30.6 HollowBlocksandFormen
Blocksandfonnersmaybe ofanysuitablematerial.
Hollowclaytilesfor the filler type shallconformto
IS39~1 (PartI).Whenrequiredtocontributeto the
structuralstrengthof a slabtheyshall:
a)bemadeofconcreteor burntclay;and
b) have a crushinsstrengthof at least 14 N/mm
2
measuredonthenetsectionwhenaxiallyloaded
inthedirectionofcompressivestressintheslab.
30.'ArraDlemeDtofReinforcement
Therecommendationslivenin26.3resardinl
maximumdistancebetweenbarsapplytoareasofsolid
concreteinthisfonnofconstruction.Thecurtailment.
anchorage and cover to reinforcement shall be as
describedbelow:
a) AtleastSOpercentof thetotalmain
reinforcementshall be carriedthroughat
the
bottom on to the
bearinland anchored in
accordancewith36.2.3.3.
b)Wherea slab.whichiscontinuousoversupports,
has beendesignedassimplysupported,
reinforcementshallbeprovidedoverthe
support
to controlcracking.Thisreinforcementshall
haveacross-sectionalareaof notlessthanone
quarterthat required in the middle of the
adjoiningspans and shall extend at least one
tenth of the clear span intoadjoining
spans.
c) In slabs with pennanentblocks,the side cover
to the reinforcement shall not be less than
10 mm. In all
othercases.covershall
be
providedaccordingto26.4.
30.8PrecutsJoistsandHoUowFillerBlocks
Theconstructionwith precast joists and hollow
concrete filler blocks shall conformto IS
6061(Part
1)and precastjoist and hollowclay fillerblocksshall
confonn to IS
6061(Part2).
31 FLATSLABS
31.1General
Thetermflat slabmeansareinforcedconcreteslab
with or withoutdrops.supportedgenerallywithout
beams.bycolumns with or without flared column
heads(seeFig.12). A flat slabmaybesolidslabor
mayhaverecessesfonnedonthesoftlt~othatthesoffit
comprises a series of ribs in two directions. The
recesses
may
befonnedbyremovableorpermanent
filler blocks. '
31.1.1 For the purposeof this
clause,thefollowing
definitionsshall apply:.
a)
Columnstrip- Column strip means a design
strip having a width of
0.2S'
2
,
butnot
greater
than0.25'ioneach side of the columncentre
line, where
I.is the span in the direction
momentsarebeingdetermined,measuredcentre
tocentreofsupportsand
'
2
is thespantransverse
IS4S6:2000
toll'measuredcentreto centreofsupports.
b)Middl~strip-Middlestripmeansadesisnstrip
boundedon each of itsoppositesides
bythe
columnstrip.
c)Panel-«Panelmeansthatpartofaslabbounded
on each of its foursidesbythecentre-lineof a
columnorcentre-linesof adjacentspans.
31.2Proportlonlnl
31.2.1ThicknessofFlatSlab
The thickness of the flat slab shall be generally
controlled
byconsiderationsof spantoeffectivedepth
ratios
givenin 23.2.
Forslabs withdropsconformingto
31.2.2.span to
effectivedepth ratios liven In23.2shallbeapplied
directly;otherwisethe span toeffectivedepth ratios
obtainedinaccordancewithprovisionsin23.2shall
bemultipliedby0.9.Forthispurpose.thelongerspan
shallbeconsidered.The minimumthicknessof slab
shall
be12Smm.
31.2.2Drop
Thedropswhenprovidedshall berectangularin plan.
and have a lengthin eachdirectionnot less thanone
thirdofthepanellengthin thatdirection.Forexterior
panels.the widthof drops at right angles to the non
continuousedgeandmeasured
fromthecentre-lineof
the
columnsshallbeequaltoone-halfthe width of
drop for interior
panels.
31.2.3ColumnHeads
Wherecolumnheadsareprovided,that portion of a
columnheadwhichlieswithinthelargestrightcircular
coneor
pyramidthathasa
vertexangleof 90°andcan
beincludedentirely withintheoutlinesof the column
and
thecolumn
head,shallbeconsideredfordesign
purposes(SttFig.12).
31.3DetermlnatioDof Bendinl Moment
31.3.1Methods01AnalysisandDesig"
It shallbepennissiblcto design the slab systemby
one of thefollowingmethods:
a) The directdesign methodasspecifiedin 31.4.
and
b)The equivalent frame method as specified
in31.5.
In each case theapplicable limitationsgiven in
31.4
and
31.Sshallbemet.
31.3.2Benc#ngMomentsinPanelswith Marginal
BeamsorWalls
Wherethe slab issupportedby a marginalbeamwith
a depthgreaterthan 1.5timesthethicknessof theslab.
orby a wall,then:
S3
a)bemadeofconcreteor burntclay;and
b) have a crushinsstrengthof at least 14 N/mm
2
measuredonthenetsectionwhenaxiallyloaded
inthedirectionofcompressivestressintheslab.
30.'ArraDlemeDtofReinforcement
Therecommendationslivenin26.3resardinl
maximumdistancebetweenbarsapplytoareasofsolid
concreteinthisfonnofconstruction.Thecurtailment.
anchorage and cover to reinforcement shall be as
describedbelow:
a) AtleastSOpercentof thetotalmain
reinforcementshall be carriedthroughat
the
bottom on to the
bearinland anchored in
accordancewith36.2.3.3.
b)Wherea slab.whichiscontinuousoversupports,
has beendesignedassimplysupported,
reinforcementshallbeprovidedoverthe
support
to controlcracking.Thisreinforcementshall
haveacross-sectionalareaof notlessthanone
quarterthat required in the middle of the
adjoiningspans and shall extend at least one
tenth of the clear span intoadjoining
spans.
c) In slabs with pennanentblocks,the side cover
to the reinforcement shall not be less than
10 mm. In all
othercases.covershall
be
providedaccordingto26.4.
30.8PrecutsJoistsandHoUowFillerBlocks
Theconstructionwith precast joists and hollow
concrete filler blocks shall conformto IS
6061(Part
1)and precastjoist and hollowclay fillerblocksshall
confonn to IS
6061(Part2).
31 FLATSLABS
31.1General
Thetermflat slabmeansareinforcedconcreteslab
with or withoutdrops.supportedgenerallywithout
beams.bycolumns with or without flared column
heads(seeFig.12). A flat slabmaybesolidslabor
mayhaverecessesfonnedonthesoftlt~othatthesoffit
comprises a series of ribs in two directions. The
recesses
may
befonnedbyremovableorpermanent
filler blocks. '
31.1.1 For the purposeof this
clause,thefollowing
definitionsshall apply:.
a)
Columnstrip- Column strip means a design
strip having a width of
0.2S'
2
,
butnot
greater
than0.25'ioneach side of the columncentre
line, where
I.is the span in the direction
momentsarebeingdetermined,measuredcentre
tocentreofsupportsand
'
2
is thespantransverse
IS4S6:2000
toll'measuredcentreto centreofsupports.
b)Middl~strip-Middlestripmeansadesisnstrip
boundedon each of itsoppositesides
bythe
columnstrip.
c)Panel-«Panelmeansthatpartofaslabbounded
on each of its foursidesbythecentre-lineof a
columnorcentre-linesof adjacentspans.
31.2Proportlonlnl
31.2.1ThicknessofFlatSlab
The thickness of the flat slab shall be generally
controlled
byconsiderationsof spantoeffectivedepth
ratios
givenin 23.2.
Forslabs withdropsconformingto
31.2.2.span to
effectivedepth ratios liven In23.2shallbeapplied
directly;otherwisethe span toeffectivedepth ratios
obtainedinaccordancewithprovisionsin23.2shall
bemultipliedby0.9.Forthispurpose.thelongerspan
shallbeconsidered.The minimumthicknessof slab
shall
be12Smm.
31.2.2Drop
Thedropswhenprovidedshall berectangularin plan.
and have a lengthin eachdirectionnot less thanone
thirdofthepanellengthin thatdirection.Forexterior
panels.the widthof drops at right angles to the non
continuousedgeandmeasured
fromthecentre-lineof
the
columnsshallbeequaltoone-halfthe width of
drop for interior
panels.
31.2.3ColumnHeads
Wherecolumnheadsareprovided,that portion of a
columnheadwhichlieswithinthelargestrightcircular
coneor
pyramidthathasa
vertexangleof 90°andcan
beincludedentirely withintheoutlinesof the column
and
thecolumn
head,shallbeconsideredfordesign
purposes(SttFig.12).
31.3DetermlnatioDof Bendinl Moment
31.3.1Methods01AnalysisandDesig"
It shallbepennissiblcto design the slab systemby
one of thefollowingmethods:
a) The directdesign methodasspecifiedin 31.4.
and
b)The equivalent frame method as specified
in31.5.
In each case theapplicable limitationsgiven in
31.4
and
31.Sshallbemet.
31.3.2Benc#ngMomentsinPanelswith Marginal
BeamsorWalls
Wherethe slab issupportedby a marginalbeamwith
a depthgreaterthan 1.5timesthethicknessof theslab.
orby a wall,then:
S3
IS 456 :2000
....-~........--r-CRITICALSECTION'OR
SHURIMMfDIATlLY
ADJACENTTOCOLUM
12 BSLABWITH DROP &COLUMN
WITHCOLUMNHEAD
,---
,
/"
,,'
I'. ANYCONCRITEINTHISARIA
TOBENEGLECTEDINTHE
CALCULATIONS
12A SLAB WITHourDROP&COLUMN
WITHOUTCOLUMN HEAD
CRITICALSECllON
FORSHEAR
12 CSLAB WITHOUT DROP"COLUMN
WITH COLUMN HEAD
NOTE -D.is the diameterof columnor columnheadtobeconsideredfordesi...anddiaeffectivedepthofalabor dropII
IIpproprillte"
FlO.12CRJ11CALSEC110NSFORSHEARIN FLAT SLABS
a) thetotalloadto becarriedby thebeamorwall
shallcomprisethoseloadsdirectlyon thewall
orbeamplusauniformlydistributedloadequal
toone-quarterof thetotalloadontheslab,and
b) the
bendingmomentson
thehalf-columnstrip
adjacenttothebeamorwallshallbeone-quarter
of thebendingmomentsfor thefll'Stinterior
columnstrip.
31.3.3TransferofBendingMomentstoColumns
Whenunbalancedgravityload,wind,earthquake,or
otherlateralloadscausetransferof
bendingmoment
betweenslab andcolumn,theflexuralstressesshall
be
investigatedusingafraction,aofthemomentgiven
by:
1
a-~-l+~aJ
3fa,
where
a.=overalldimensionoftilecriticalsection
for shear in the direction in which
momentacts,and
a
2=overalldimensionofthecriticalsection
for sheartransverseto thedirectionin
whichmomentacts.
A slabwidthbetweenlinesthatareoneandone-half
slabor drop
panelthickness;1.5D, on each
sideof
the
columnorcapitalmaybeconsideredeffective,D
beingthesizeof thecolumn.
Concentrationofreinforcementovercolumnheadby
closerspacingoradditionalreinforcementmaybeused
to resist
themomentonthissection:
31.4DlreetDestpMethod
31.4.1Limitations
Slabsystemdesignedbythedirectdesignmethodshall
fulfilthefollowingconditions:
a)Thereshallbeminimumof threecontinuous
spansineachdirection,
b) Thepanelsshallberectangular,andtheratioof
thelongerspantotheshorterspanwithinapanel
shallnotbegreaterthan2.0,
c) It shall be
permissibletooffsctcolumnsto a
maximumof 10 percent of the span in the
direction of the offset notwithstanding the
provisionin (b),
d) The
successivespan
lenllhsin eachdirection
shall notdifferby morethanone-thirdofthe
longerspan.Theend"spansmaybeshorterbut
not
longerthan
theinteriorspans,and
....-~........--r-CRITICALSECTION'OR
SHURIMMfDIATlLY
ADJACENTTOCOLUM
12 BSLABWITH DROP &COLUMN
WITHCOLUMNHEAD
,---
,
/"
,,'
I'. ANYCONCRITEINTHISARIA
TOBENEGLECTEDINTHE
CALCULATIONS
12A SLAB WITHourDROP&COLUMN
WITHOUTCOLUMN HEAD
CRITICALSECllON
FORSHEAR
12 CSLAB WITHOUT DROP"COLUMN
WITH COLUMN HEAD
NOTE -D.is the diameterof columnor columnheadtobeconsideredfordesi...anddiaeffectivedepthofalabor dropII
IIpproprillte"
FlO.12CRJ11CALSEC110NSFORSHEARIN FLAT SLABS
a) thetotalloadto becarriedby thebeamorwall
shallcomprisethoseloadsdirectlyon thewall
orbeamplusauniformlydistributedloadequal
toone-quarterof thetotalloadontheslab,and
b) the
bendingmomentson
thehalf-columnstrip
adjacenttothebeamorwallshallbeone-quarter
of thebendingmomentsfor thefll'Stinterior
columnstrip.
31.3.3TransferofBendingMomentstoColumns
Whenunbalancedgravityload,wind,earthquake,or
otherlateralloadscausetransferof
bendingmoment
betweenslab andcolumn,theflexuralstressesshall
be
investigatedusingafraction,aofthemomentgiven
by:
1
a-~-l+~aJ
3fa,
where
a.=overalldimensionoftilecriticalsection
for shear in the direction in which
momentacts,and
a
2=overalldimensionofthecriticalsection
for sheartransverseto thedirectionin
whichmomentacts.
A slabwidthbetweenlinesthatareoneandone-half
slabor drop
panelthickness;1.5D, on each
sideof
the
columnorcapitalmaybeconsideredeffective,D
beingthesizeof thecolumn.
Concentrationofreinforcementovercolumnheadby
closerspacingoradditionalreinforcementmaybeused
to resist
themomentonthissection:
31.4DlreetDestpMethod
31.4.1Limitations
Slabsystemdesignedbythedirectdesignmethodshall
fulfilthefollowingconditions:
a)Thereshallbeminimumof threecontinuous
spansineachdirection,
b) Thepanelsshallberectangular,andtheratioof
thelongerspantotheshorterspanwithinapanel
shallnotbegreaterthan2.0,
c) It shall be
permissibletooffsctcolumnsto a
maximumof 10 percent of the span in the
direction of the offset notwithstanding the
provisionin (b),
d) The
successivespan
lenllhsin eachdirection
shall notdifferby morethanone-thirdofthe
longerspan.Theend"spansmaybeshorterbut
not
longerthan
theinteriorspans,and
where
s,=
K.=
e)ThedeSiSDliveloadshallnotexceedthreetimes
thedesiandead load.
31.4.2TotalDesignMoment/oraSpan
31.4.11Inthedirectdesipmethod,thetotaldesign
momentfor a span shall bedeterminedfor astrip
boundedlaterallybythecentre-lineof thepane)on
eachsideof thecentre-lineofthesupports.
31.4.2.2Theabsolutesumofthepositiveandaverase
ne,ativebendinamomentaineachdirectionshallbe
takenu:
M
Win
o·
8
where
M"=totalmoment;
W=designload on anarea'2'.;
In=clearspanextendingfromface to face of
columns,capitals,
bracketsor walls, but
not less than
0.651.;
'I=lengthof span inthedirectionof M
o
;and
'2=lengthof spantransverseto ' r
31.4.2.3 Circularsupportsshall be treated as square
supportshavingthe same area.
31.4.Z.4Whenthetransversespan of the panels on
eithersideof
thecentre-lineofsupportsvaries,1
2
shall
be taken as the averageof thetransverse
spans.
31.4.Z.5Whenthespanadjacentandparalleltoanedge
isbeingconsidered,the distancefromthe edge tothe
centre-line of the panel shan be substituted forlz
in31.4.2.2.
31.4.3Negativ«andPositiveDesignMoments
31.4.3.1ThenegativedesiBnmomentshallbelocated
at the face ofrectangularsupports,circularsupports
being treated as squaresupports havingthesame
area.
31.4.3.2In an interiorspan,the total designmoment
M
u
shallbedistributedin thefollowingproportions:
Negativedesign
moment 0.65
Positivedesignmoment 0.35
31.4.3.3 In an end span, the total design moment
M"
shall bedistributedin thefollowingproportions:
Interiornegativedesign
moment:
0.7S_
O.l~
1+-
at
Positivedesignmoment:
0.63-O.2~
1+
a
c
5S
IS456:ZOOO
Exteriornegativedesign moment:
O.6S
--.
1+-
a
c
a
cis the ratio offlexuralstiffnessof theexterior
columnsto theflexuralstiffnessoftheslabatajoint
takenin thedirection
momentsare beingdetermined
and is liven
by
EX
a•=:.a.
eK
•
sum of the flexuralstiffnessof the
columnsmeetingat thejoint; and
flexural
stiffnessof the slab, expressed
asmomentper.unitrotation.
31.4.3.4Itshallbepermissibleto modifythesedesign
momentsbyupto10percent.so10nlasthetotaldesign
moment,M.,for the panel in thedirectionconsidered
is not less than thatrequired by31.4.1.1.
31.4.3.5 Thenegativemoment section shall be
designedtoresisttheIB1Jcrofthetwointeriornegative
designmomentsdeterminedforthespansframinginto
a common support unless an analysis is made to
distributetheunbalancedmomentinaccordance
with
thestiffnessoftheadjoining
parts.
31.4.4DistributionofBendingMo~,.tsAcrossthe
PanelWidth
Bendingmomentsatcriticalcross-sectionshallbe
distributedto thecolumnstripsandmiddlestripsas
specifiedin31.5.5asapplicable.
31.4.5MomentsinColumns
31.4.5.1Columnsbuiltintegrallywiththeslabsystem
shall
bedesignedtoresistmomentsarisingfromloads
onthe slab
system.
31.4.5.1Ataninteriorsupport, thesupporting
membersaboveandbelowthe slab shallbedesigned
toresist
themomeatMgivenbythefollowingequation,
indirectproportiontotheirstiffnesses unlessageneral
analysisis made:
(W
d+O.Sw,)1
11:-w~I;I:'
M=O.OS 1
1+-
al:
where
Wei' WI=designdeadandlive loads
respectively,per unitarea;
'2=length of span transverse to the
directionof
M;
s,=
K.=
e)ThedeSiSDliveloadshallnotexceedthreetimes
thedesiandead load.
31.4.2TotalDesignMoment/oraSpan
31.4.11Inthedirectdesipmethod,thetotaldesign
momentfor a span shall bedeterminedfor astrip
boundedlaterallybythecentre-lineof thepane)on
eachsideof thecentre-lineofthesupports.
31.4.2.2Theabsolutesumofthepositiveandaverase
ne,ativebendinamomentaineachdirectionshallbe
takenu:
M
Win
o·
8
where
M"=totalmoment;
W=designload on anarea'2'.;
In=clearspanextendingfromface to face of
columns,capitals,
bracketsor walls, but
not less than
0.651.;
'I=lengthof span inthedirectionof M
o
;and
'2=lengthof spantransverseto ' r
31.4.2.3 Circularsupportsshall be treated as square
supportshavingthe same area.
31.4.Z.4Whenthetransversespan of the panels on
eithersideof
thecentre-lineofsupportsvaries,1
2
shall
be taken as the averageof thetransverse
spans.
31.4.Z.5Whenthespanadjacentandparalleltoanedge
isbeingconsidered,the distancefromthe edge tothe
centre-line of the panel shan be substituted forlz
in31.4.2.2.
31.4.3Negativ«andPositiveDesignMoments
31.4.3.1ThenegativedesiBnmomentshallbelocated
at the face ofrectangularsupports,circularsupports
being treated as squaresupports havingthesame
area.
31.4.3.2In an interiorspan,the total designmoment
M
u
shallbedistributedin thefollowingproportions:
Negativedesign
moment 0.65
Positivedesignmoment 0.35
31.4.3.3 In an end span, the total design moment
M"
shall bedistributedin thefollowingproportions:
Interiornegativedesign
moment:
0.7S_
O.l~
1+-
at
Positivedesignmoment:
0.63-O.2~
1+
a
c
5S
IS456:ZOOO
Exteriornegativedesign moment:
O.6S
--.
1+-
a
c
a
cis the ratio offlexuralstiffnessof theexterior
columnsto theflexuralstiffnessoftheslabatajoint
takenin thedirection
momentsare beingdetermined
and is liven
by
EX
a•=:.a.
eK
•
sum of the flexuralstiffnessof the
columnsmeetingat thejoint; and
flexural
stiffnessof the slab, expressed
asmomentper.unitrotation.
31.4.3.4Itshallbepermissibleto modifythesedesign
momentsbyupto10percent.so10nlasthetotaldesign
moment,M.,for the panel in thedirectionconsidered
is not less than thatrequired by31.4.1.1.
31.4.3.5 Thenegativemoment section shall be
designedtoresisttheIB1Jcrofthetwointeriornegative
designmomentsdeterminedforthespansframinginto
a common support unless an analysis is made to
distributetheunbalancedmomentinaccordance
with
thestiffnessoftheadjoining
parts.
31.4.4DistributionofBendingMo~,.tsAcrossthe
PanelWidth
Bendingmomentsatcriticalcross-sectionshallbe
distributedto thecolumnstripsandmiddlestripsas
specifiedin31.5.5asapplicable.
31.4.5MomentsinColumns
31.4.5.1Columnsbuiltintegrallywiththeslabsystem
shall
bedesignedtoresistmomentsarisingfromloads
onthe slab
system.
31.4.5.1Ataninteriorsupport, thesupporting
membersaboveandbelowthe slab shallbedesigned
toresist
themomeatMgivenbythefollowingequation,
indirectproportiontotheirstiffnesses unlessageneral
analysisis made:
(W
d+O.Sw,)1
11:-w~I;I:'
M=O.OS 1
1+-
al:
where
Wei' WI=designdeadandlive loads
respectively,per unitarea;
'2=length of span transverse to the
directionof
M;
IS456:2000
I.=lengthof theclearspan in the
directionof
M,measured
facetoface
of
supports;
IK
a
c=
--&'I'whereK
c
andK.areasdefined
K.
in31.4.3.3;and
w;.I'landI:.referto the shorterspan.
31.4.6EffectsofPatternLoading
Inthedirectdesignmethod.whentheratioofliveload
to deadloadexceedsO.S:
a) thesumoftheflexuralstiffnessesofthecolumns
above andbelowthe slab.IKe'shall be such
thatex.is notlessthantheappropriate minimum
valueex.IltIaspecifiedin Tablet7.or
b) if the sum of the flexural stiffnesses of the
columns.
IKe'doesnotsatisfy(a).thepositive
designmomentsforthepanelsballbe multiplied
by thecoefficientP.given by thefollowing
equation:
b) Eachsuch
framemaybe
analyzedinitsentirety,
or, forverticalloading,each floorthereofand
the roof may be
analyzedseparatelywith its
columnsbeingassumed
fixedat theirremote
ends.Whereslabsarethusanalyzedseparately,
it maybeassumedindeterminingthe bending
momentat a givensupportthattheslabisfixed
at any support two panels distant therefrom
providedtheslabcontinues beyondthepoint.
c) Forthepurposeofdeterminingrelativestiffness
ofmembers.themomentof inertiaof any slab
or
columnmay beassumedto be that of the
grosscross-sectionof theconcrete alone.
d)Variationsofmomentof inertiaalongtheaxisoftheslabonaccountofprovisionofdropsshall
be
takenintoaccount.In the case ofrecessed
or coffered slab which is made solid in the
regionofthecolumns.thestiffeningeffectmay
be
ignoredprovidedthe solid part of the slab
doesnotextendmorethan
0.15'eI'intothespan
measuredfromthecentre-lineof the columns.
Thestiffeningeffectofflaredcolumnheadsmay
be
ignored.
31.5.2LoadingPattern
31.5.2.1When the loading pattern is known. the
structureshall
beanalyzedforthe loadconcerned.
Table17Minimum
PermissibleValuesofex
c
(Clause31.4.6)
31.5.2.1Whenthelive load isvariablebut does not
exceedthree-quartersofthedead load.or thenature
of the liveload is suchthat all
panelswillbe loaded
simultaneously, the maximum moments may be
assumedtooccurat allsectionswhenfulldesignlive
loadis on the
entireslabsystem.
ex.istheratioofflexuralstiffnessof thecolumnsabove
andbelowtheslabto theflexuralstiffnessof theslabs
at a joint taken in thedirection
moments
arebeing
determinedand is givenby:
ex=IKe:
cIK
•
whereK
c
andK.areflexuralstiffnessesof columnand
slabrespectively.
31.5Equivalent Frame Method
31.5.1Assumptions
The bending moments and shear forces may be
determined by an analysis of the structure as a
continuousframeandthe
followingassumptionsmay
bemade:
a) Thestructureshall beconsideredto bemadeup
of equivalent frames on column lines taken
longitudinally and transversely through the
building. Each frame consists of a row of
equivalentcolumns or supports, bounded
laterallyby
thecentre-lineof thepanelon each
side of thecentre-lineof the columns or
supports.Framesadjacent'andparalleltoanedge
shall be
boundedby the edge and thecentre
lineoftheadjacentpanel.
S6
ImpoHdLoadIDelldLoad
(1)
O.S
1.0
1.0
1.0
1.0
1.0
2.0
2.0
2.0
2.0
2.0
3.0
3.0
3.0
3.0
3.0
Ratlo~
II
(2)
O.Sto2.0
0.5
0,8
1.0
1.25
2.0O.S
0.8
1.0
1.2S
2.0
0.5
0.8
1.0
1.25
2.0
VII.ora....
(3)
o
0.6
0.7
0.7
0.8
1.2
1.31.5
1.6
1.9
4.9
1.8
2.0
2.3
2.8
13.0
I.=lengthof theclearspan in the
directionof
M,measured
facetoface
of
supports;
IK
a
c=
--&'I'whereK
c
andK.areasdefined
K.
in31.4.3.3;and
w;.I'landI:.referto the shorterspan.
31.4.6EffectsofPatternLoading
Inthedirectdesignmethod.whentheratioofliveload
to deadloadexceedsO.S:
a) thesumoftheflexuralstiffnessesofthecolumns
above andbelowthe slab.IKe'shall be such
thatex.is notlessthantheappropriate minimum
valueex.IltIaspecifiedin Tablet7.or
b) if the sum of the flexural stiffnesses of the
columns.
IKe'doesnotsatisfy(a).thepositive
designmomentsforthepanelsballbe multiplied
by thecoefficientP.given by thefollowing
equation:
b) Eachsuch
framemaybe
analyzedinitsentirety,
or, forverticalloading,each floorthereofand
the roof may be
analyzedseparatelywith its
columnsbeingassumed
fixedat theirremote
ends.Whereslabsarethusanalyzedseparately,
it maybeassumedindeterminingthe bending
momentat a givensupportthattheslabisfixed
at any support two panels distant therefrom
providedtheslabcontinues beyondthepoint.
c) Forthepurposeofdeterminingrelativestiffness
ofmembers.themomentof inertiaof any slab
or
columnmay beassumedto be that of the
grosscross-sectionof theconcrete alone.
d)Variationsofmomentof inertiaalongtheaxisoftheslabonaccountofprovisionofdropsshall
be
takenintoaccount.In the case ofrecessed
or coffered slab which is made solid in the
regionofthecolumns.thestiffeningeffectmay
be
ignoredprovidedthe solid part of the slab
doesnotextendmorethan
0.15'eI'intothespan
measuredfromthecentre-lineof the columns.
Thestiffeningeffectofflaredcolumnheadsmay
be
ignored.
31.5.2LoadingPattern
31.5.2.1When the loading pattern is known. the
structureshall
beanalyzedforthe loadconcerned.
Table17Minimum
PermissibleValuesofex
c
(Clause31.4.6)
31.5.2.1Whenthelive load isvariablebut does not
exceedthree-quartersofthedead load.or thenature
of the liveload is suchthat all
panelswillbe loaded
simultaneously, the maximum moments may be
assumedtooccurat allsectionswhenfulldesignlive
loadis on the
entireslabsystem.
ex.istheratioofflexuralstiffnessof thecolumnsabove
andbelowtheslabto theflexuralstiffnessof theslabs
at a joint taken in thedirection
moments
arebeing
determinedand is givenby:
ex=IKe:
cIK
•
whereK
c
andK.areflexuralstiffnessesof columnand
slabrespectively.
31.5Equivalent Frame Method
31.5.1Assumptions
The bending moments and shear forces may be
determined by an analysis of the structure as a
continuousframeandthe
followingassumptionsmay
bemade:
a) Thestructureshall beconsideredto bemadeup
of equivalent frames on column lines taken
longitudinally and transversely through the
building. Each frame consists of a row of
equivalentcolumns or supports, bounded
laterallyby
thecentre-lineof thepanelon each
side of thecentre-lineof the columns or
supports.Framesadjacent'andparalleltoanedge
shall be
boundedby the edge and thecentre
lineoftheadjacentpanel.
S6
ImpoHdLoadIDelldLoad
(1)
O.S
1.0
1.0
1.0
1.0
1.0
2.0
2.0
2.0
2.0
2.0
3.0
3.0
3.0
3.0
3.0
Ratlo~
II
(2)
O.Sto2.0
0.5
0,8
1.0
1.25
2.0O.S
0.8
1.0
1.2S
2.0
0.5
0.8
1.0
1.25
2.0
VII.ora....
(3)
o
0.6
0.7
0.7
0.8
1.2
1.31.5
1.6
1.9
4.9
1.8
2.0
2.3
2.8
13.0
31.5.2.3For other conditions of live load/dead load
ratioand whenall panelsarenot loadedsimultaneously:
a) maximum positive moment near midspan of a
panel
maybe assumed to occur when three
quarters of the full design live load is on the
panel and on alternate
panels;and
b)maximum negative moment in the slab at a
support
maybe assumed to occurwhenthree
quarters of the full design live load is on
the
adjacent panels only.
31.5.1.4In no caseshall designmomentsbetakento
be less than those occurring with full design live load
on
allpanels.
31.5.3NegativeDesignMoment
31.5.3.1At interior supports, the critical sectionfor
negative
moment, in both the column strip and middle
strip,shall be takenatthe faceofrectilinear supports,
but in no case at a distance greater than 0.175IIfrom
the centre of the column whereIIis the length of the
span in the direction moments are being determined,
measured centre-to-centre
ofsupports.
31.5.3.2 At exterior supports provided with brackets
or capitals, the critical section for negative moment in
the direction perpendicular to the edge shall
betaken
at a distance from the face of the supporting element
not greater than one-half the projection of the bracket
or capital beyond the face of the supporting element.
31.5.3.3 Circular or regular polygon shaped supports
shall be treated as square supports having the same
area.
31.5.4ModificationofMaximumMoment
Momentsdeterminedbymeansoftheequivalentframe
method,
forslabs which fulfil the limitations of 31.4
maybe reduced in such proportion that the numerical
sum of the positive and
averagenegative moments is
not less than the value of total design moment
M"
specifiedin31.4.2.2.
31.5.5 DistributionofBendingMomentAcross the
PanelWidth
31.5.5.1Columnstrip:Negativemomentat an interior
support
Ataninteriorsupport,the column strip shall be
designed to resist
7Spercent of the total negative
moment in the panel at that support.
31.5.5.2Columnstrip:Negativemomentatanexterior
support
a) At an exterior support. the column strip shall be
designed to resist the total negative moment in
the panel at that support.
b) Where the exterior support consists of a column
or a wall extending for a distance equal to or
2116815/07-9
57
IS456:
2000
greater than three-quartersof the value of1
2
,
the
length
ofspantransverseto thedirection
moments are being determined, the exterior
negative moment shall beconsideredto be
uniformly distributed across the length
'2'
31.5.5.3Columnstrip: Positivemomentforeachspan
For each span. the column strip shall be designed to
resist 60 percent of the total positive moment in the
panel.
31.5.5.4Momentsin the middle strip
The middle strip shall be designed on the following
bases:
a) That portion of the design moment not resisted
bythe column strip shall be assigned to the
adjacent middle strips.
b) Eachmiddlestripshallbeproportionedto resist
the sum of the moments assigned to
itstwo half
middle strips.
c) The middlestripadjacentand parallelto an edge
supported
byawallshall be proportioned to
resist twice the moment assigned to half the
middle strip corresponding to the first row of
interior columns.
31.6ShearinFlatSlab
31.6.1
Thecriticalsectionfor shearshallbe at a
distanced/2from the periphery of the column/capital/
drop panel,perpendiculartothe planeof theslab where
dis the effective depth of the section(seeFig. 12).
TIleshapeinplanisgeometricallysimilarto thesupport
immediately below the slab
(seeFig. 13A and 13B).
NOTE- Forcolumnsectionswithre-entrantangles.thecritical
sectionshallbetakenasindicatedin Fig. 13Cand130.
31.6.1.1In the case of columns near the free edge of
a slab, the critical section
shallbe taken as shown in
Fig. 14.
31.6.1.~ When openings in flat slabs are located at a
distance less than ten times the thickness of the slab
from a concentratedreactionor whenthe openings are
located within the column strips. the critical sections
specified in
31.6.1shallbemodified so that the part of
the periphery of
thecritical section which is enclosed
byradial projectionsof the openings to the centroid of
the reaction area
shallbeconsideredineffective
(.\"eeFig.15),and openings shall notencroachupon
column head.
31.6.2CalculationofShear Stress
The shear stress
tvshall be the sum of the values
calculated according to31.6.2.1and 31.6.2.2.
31.6.2.1 The nominal shear stress in flat slabs shall
be
takenasV I b dwhereVis theshear forcedue to design
load,
bitisth~)periphery of the critical section anddis
the effective depth.
ratioand whenall panelsarenot loadedsimultaneously:
a) maximum positive moment near midspan of a
panel
maybe assumed to occur when three
quarters of the full design live load is on the
panel and on alternate
panels;and
b)maximum negative moment in the slab at a
support
maybe assumed to occurwhenthree
quarters of the full design live load is on
the
adjacent panels only.
31.5.1.4In no caseshall designmomentsbetakento
be less than those occurring with full design live load
on
allpanels.
31.5.3NegativeDesignMoment
31.5.3.1At interior supports, the critical sectionfor
negative
moment, in both the column strip and middle
strip,shall be takenatthe faceofrectilinear supports,
but in no case at a distance greater than 0.175IIfrom
the centre of the column whereIIis the length of the
span in the direction moments are being determined,
measured centre-to-centre
ofsupports.
31.5.3.2 At exterior supports provided with brackets
or capitals, the critical section for negative moment in
the direction perpendicular to the edge shall
betaken
at a distance from the face of the supporting element
not greater than one-half the projection of the bracket
or capital beyond the face of the supporting element.
31.5.3.3 Circular or regular polygon shaped supports
shall be treated as square supports having the same
area.
31.5.4ModificationofMaximumMoment
Momentsdeterminedbymeansoftheequivalentframe
method,
forslabs which fulfil the limitations of 31.4
maybe reduced in such proportion that the numerical
sum of the positive and
averagenegative moments is
not less than the value of total design moment
M"
specifiedin31.4.2.2.
31.5.5 DistributionofBendingMomentAcross the
PanelWidth
31.5.5.1Columnstrip:Negativemomentat an interior
support
Ataninteriorsupport,the column strip shall be
designed to resist
7Spercent of the total negative
moment in the panel at that support.
31.5.5.2Columnstrip:Negativemomentatanexterior
support
a) At an exterior support. the column strip shall be
designed to resist the total negative moment in
the panel at that support.
b) Where the exterior support consists of a column
or a wall extending for a distance equal to or
2116815/07-9
57
IS456:
2000
greater than three-quartersof the value of1
2
,
the
length
ofspantransverseto thedirection
moments are being determined, the exterior
negative moment shall beconsideredto be
uniformly distributed across the length
'2'
31.5.5.3Columnstrip: Positivemomentforeachspan
For each span. the column strip shall be designed to
resist 60 percent of the total positive moment in the
panel.
31.5.5.4Momentsin the middle strip
The middle strip shall be designed on the following
bases:
a) That portion of the design moment not resisted
bythe column strip shall be assigned to the
adjacent middle strips.
b) Eachmiddlestripshallbeproportionedto resist
the sum of the moments assigned to
itstwo half
middle strips.
c) The middlestripadjacentand parallelto an edge
supported
byawallshall be proportioned to
resist twice the moment assigned to half the
middle strip corresponding to the first row of
interior columns.
31.6ShearinFlatSlab
31.6.1
Thecriticalsectionfor shearshallbe at a
distanced/2from the periphery of the column/capital/
drop panel,perpendiculartothe planeof theslab where
dis the effective depth of the section(seeFig. 12).
TIleshapeinplanisgeometricallysimilarto thesupport
immediately below the slab
(seeFig. 13A and 13B).
NOTE- Forcolumnsectionswithre-entrantangles.thecritical
sectionshallbetakenasindicatedin Fig. 13Cand130.
31.6.1.1In the case of columns near the free edge of
a slab, the critical section
shallbe taken as shown in
Fig. 14.
31.6.1.~ When openings in flat slabs are located at a
distance less than ten times the thickness of the slab
from a concentratedreactionor whenthe openings are
located within the column strips. the critical sections
specified in
31.6.1shallbemodified so that the part of
the periphery of
thecritical section which is enclosed
byradial projectionsof the openings to the centroid of
the reaction area
shallbeconsideredineffective
(.\"eeFig.15),and openings shall notencroachupon
column head.
31.6.2CalculationofShear Stress
The shear stress
tvshall be the sum of the values
calculated according to31.6.2.1and 31.6.2.2.
31.6.2.1 The nominal shear stress in flat slabs shall
be
takenasV I b dwhereVis theshear forcedue to design
load,
bitisth~)periphery of the critical section anddis
the effective depth.
15456:2000
13A
SUPPORT
CRITICAL
SECTION
Id/2
~tT
SUliPORTSECTION
COLUMNICOLUMNHEAD
I
L_
r-------l
I ~~.';'a:':'';',':I
I
....:~:..t:••::'...
• I ,••'..
SUPPORT
SECTION
SUPPORT
SECTION
rr
d/2
[
CRITICAL
SECTION
-,
-l.
I.,,,'..•:)d/2
I
;......""'.'
•.1""•'4\.
I
~:~":'.,~.r:~I.""."..
d/2
L-
1
;i;--t
NOTE-di.theeffec:tivedepthofthenatslab/drop.
FlO.13CarneALSScnONSINPLANFORSHEARINfLATSLABS
~'ReE
L.-reDGE
I 'VCRITICAL
I ~.'•••'. seCTION
."".~.
I :~....~:~~
I
·•.;.
~~;....
I ~,".. '
I~__ d/2
~/~--T
"A
L__~_
CORNeR
COLUMN CRITICAL
SeCTION
148
FREE
CORNER
Fro.14EFFEcrOFFRBBBOOBSONCRrneALSBC110NFORSHEAR
31.6.2.2Whenunbalancedgravity load, wind,
earthquakeor otherfo~scausetransferofbending
momentbetweenslabandcolumn.afraction(I-ex)
of the moment shall be considered transferred by
eccentricity of the shear about the centroid ofthe
criticalsection.Shearstressesshallbetakenallvarying
linearlyaboutthecentroidof thecriticalsection.The
valueofashallbeobtainedfromtheequationgiven
in31.3.3.
31.6.3Permissible
ShearStress
31.6.3.1When shearreinf~ment isnotprovided.
thecalculatedshearscressatthecriticalsectionshall
notexceedk."C~.
S8
13A
SUPPORT
CRITICAL
SECTION
Id/2
~tT
SUliPORTSECTION
COLUMNICOLUMNHEAD
I
L_
r-------l
I ~~.';'a:':'';',':I
I
....:~:..t:••::'...
• I ,••'..
SUPPORT
SECTION
SUPPORT
SECTION
rr
d/2
[
CRITICAL
SECTION
-,
-l.
I.,,,'..•:)d/2
I
;......""'.'
•.1""•'4\.
I
~:~":'.,~.r:~I.""."..
d/2
L-
1
;i;--t
NOTE-di.theeffec:tivedepthofthenatslab/drop.
FlO.13CarneALSScnONSINPLANFORSHEARINfLATSLABS
~'ReE
L.-reDGE
I 'VCRITICAL
I ~.'•••'. seCTION
."".~.
I :~....~:~~
I
·•.;.
~~;....
I ~,".. '
I~__ d/2
~/~--T
"A
L__~_
CORNeR
COLUMN CRITICAL
SeCTION
148
FREE
CORNER
Fro.14EFFEcrOFFRBBBOOBSONCRrneALSBC110NFORSHEAR
31.6.2.2Whenunbalancedgravity load, wind,
earthquakeor otherfo~scausetransferofbending
momentbetweenslabandcolumn.afraction(I-ex)
of the moment shall be considered transferred by
eccentricity of the shear about the centroid ofthe
criticalsection.Shearstressesshallbetakenallvarying
linearlyaboutthecentroidof thecriticalsection.The
valueofashallbeobtainedfromtheequationgiven
in31.3.3.
31.6.3Permissible
ShearStress
31.6.3.1When shearreinf~ment isnotprovided.
thecalculatedshearscressatthecriticalsectionshall
notexceedk."C~.
S8
IS4~6:2000
r-- COLUMN
I
i:':~:~'..:~~:; ~~~'J~~~~
I ''''·.~~:.~''':-+-AI
I 0'-'·".'
, j enL ~tr
COLUMN
I
I
:'-CRITICAL
ISECTION
,
I__.I
..L
d
,.--
/2I
, 1 ..................
11I6
I
I
J :
«ni
r
L
- -
OPENING
.......---4M--SUBTRACTFROM
PERIPHERYOPENING
15A 158
PENlNG
,
,
I
I
t
I ...-CRITICAL
I , SECTION
"----...--..J
1St
I I
I I
I~,,.0..'--TCOLUMN
I ·:..•..;..I
, ~oj,• ':'.""..:"--CRITICAL
: il~:·'!:~. ISECTION
I Il.. J
•REGARDOPENING
ASFREEEDGE
15D
FlO.15EFFECfOFOPENINGSONCRmCALSEmONFORSH£AR
where
k.=(O.S+Pc)but notgreaterthan 1,Pcbeingthe
ratioof shortside
tolongsideofthecolumn!
capital;and
tt=0.25[l;;inlimitstate method ofdesign,
and 0.16[l;;inworkingstress method of
design.
31.6.3.2 Whenthe shear stress at the criticalsection
exceeds the valuegivenin 31.6.3.1, but less than
1.S1:(shear reinforcement shallbeprovided. If the
shearstressexceedsI.S1
c
tthe flat stab shall be
redesigned.Shear stresses shallbeinvestigatedat
successivesectionsmoredistantfromthesupportand
shearreinforcement
shallbeprovidedup to asection
wherethe shear stressdoes notexceed0.5
t.While
c
designing the shearreinforcement,the shear stress
carried
bythe concreteshall beassumedto be 0.5
t~
andreinforcementshall carrytheremainingshear.
31.7SlabReinforcement
31.7.1 Spacing
The spacing of bars in a flat slab, shall not exceed
2 times the slabthickness,except
wherea slab is of
cellular or ribbed construction.
31.7.1AreaofReinforcement
Whendroppanels~used.thethicknessofdroppanel
fordetermination
ofareaofreinforcementshallbe the
lesserof the
following:
a)Thicknessof'drop,and
b)Thicknessofslabplus onequarter the distance
between
edgeof drop and edgepfcapital,
31.7.3Miniml4nlLengthofReinforcement
a)Reinforcement inflatslabsshallhave the
minimumlengthsspecifiedin Fig.16.Larger
lengthsofreinforcementshall beprovidedwhen
requiredbyanalysis.
b)
Whereadjacentspansare
unequal.theextension
of
negativereinforcementbeyondeach face of
thecommoncolumnshallbebasedonthelonger
span.
e) Thelengthofreinforcementfor slabsin frames
not braced against
sidewaysand for slabs
resistinglateral loads shall bedetermined
by
analysisbut shall not be less than those
prescribedin Fig. 16.
S9
r-- COLUMN
I
i:':~:~'..:~~:; ~~~'J~~~~
I ''''·.~~:.~''':-+-AI
I 0'-'·".'
, j enL ~tr
COLUMN
I
I
:'-CRITICAL
ISECTION
,
I__.I
..L
d
,.--
/2I
, 1 ..................
11I6
I
I
J :
«ni
r
L
- -
OPENING
.......---4M--SUBTRACTFROM
PERIPHERYOPENING
15A 158
PENlNG
,
,
I
I
t
I ...-CRITICAL
I , SECTION
"----...--..J
1St
I I
I I
I~,,.0..'--TCOLUMN
I ·:..•..;..I
, ~oj,• ':'.""..:"--CRITICAL
: il~:·'!:~. ISECTION
I Il.. J
•REGARDOPENING
ASFREEEDGE
15D
FlO.15EFFECfOFOPENINGSONCRmCALSEmONFORSH£AR
where
k.=(O.S+Pc)but notgreaterthan 1,Pcbeingthe
ratioof shortside
tolongsideofthecolumn!
capital;and
tt=0.25[l;;inlimitstate method ofdesign,
and 0.16[l;;inworkingstress method of
design.
31.6.3.2 Whenthe shear stress at the criticalsection
exceeds the valuegivenin 31.6.3.1, but less than
1.S1:(shear reinforcement shallbeprovided. If the
shearstressexceedsI.S1
c
tthe flat stab shall be
redesigned.Shear stresses shallbeinvestigatedat
successivesectionsmoredistantfromthesupportand
shearreinforcement
shallbeprovidedup to asection
wherethe shear stressdoes notexceed0.5
t.While
c
designing the shearreinforcement,the shear stress
carried
bythe concreteshall beassumedto be 0.5
t~
andreinforcementshall carrytheremainingshear.
31.7SlabReinforcement
31.7.1 Spacing
The spacing of bars in a flat slab, shall not exceed
2 times the slabthickness,except
wherea slab is of
cellular or ribbed construction.
31.7.1AreaofReinforcement
Whendroppanels~used.thethicknessofdroppanel
fordetermination
ofareaofreinforcementshallbe the
lesserof the
following:
a)Thicknessof'drop,and
b)Thicknessofslabplus onequarter the distance
between
edgeof drop and edgepfcapital,
31.7.3Miniml4nlLengthofReinforcement
a)Reinforcement inflatslabsshallhave the
minimumlengthsspecifiedin Fig.16.Larger
lengthsofreinforcementshall beprovidedwhen
requiredbyanalysis.
b)
Whereadjacentspansare
unequal.theextension
of
negativereinforcementbeyondeach face of
thecommoncolumnshallbebasedonthelonger
span.
e) Thelengthofreinforcementfor slabsin frames
not braced against
sidewaysand for slabs
resistinglateral loads shall bedetermined
by
analysisbut shall not be less than those
prescribedin Fig. 16.
S9
IS4S6:2000
-~
MINIMUM
!
r"";..ltIItCENt...oe
~0'lteE"
..~..A...t.IC1I0N
WitHOUTDftOft.....NIL
10
RIMA.NOIR
~~
;
it-t------t-ir:t-r-----:-+-~~~~-H
!I
II
,.I-tlO"''''
,
~jIII~c., r-C-~~ -.....c==OPjill,
'1.~ ~·l--c-4 I-c-,
•~ Ir"'""''''"'... ~
10
10
RIMAINDIR
I~0-.'("'... jill
I.-"'r'I tlO__ ~
.,
......c ......
--I.'~ ~\.c
/ ~,
r"+!f-----or" ~ ,,~----PII ...
::t~..o"'''' f -~- f--I'10"''''-~C
..I.......NOIR, ""''''"'..._ 'I"''''"'... ~~
!~
H----lr-:--:-:--------J.-t--::=--------;!'%H
ip
1-+----l~H----~~--¥f-i-----~---~~
!ia
*=a
IXT.lll011-DI:-CLIAIts.....N-l,,-~rCLIAIt '''AN'''.r--
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INOSLA.CONTI,,"MVI ICONtlNUITY ....OVOIO. CliOSLA.COHflNUI""
BarLengthfmmFac«ofSlqIport
MinimumLength MuimumLenath
Mark a b c d e J g
Length 0.14/, 0.201. 0.22I. 0.30 I. 0.33/. 0.201. 0.24/.
•BentbanatcllccriorsupportsmaybeusedifapneraIanalyaisisniIde.
NOTS.....Dis!hediamecerofCbccolumnandthedi.'IICI\SionofCbcrcetanpllrcolUlllDinthedinodon...
COIlIiderltion.
FlO.16MlNlMUMBENDJOINTLOCAll0NSANDEXTENSIONSPORRmNFoRCBMENT
INFLATSLABS
60
-~
MINIMUM
!
r"";..ltIItCENt...oe
~0'lteE"
..~..A...t.IC1I0N
WitHOUTDftOft.....NIL
10
RIMA.NOIR
~~
;
it-t------t-ir:t-r-----:-+-~~~~-H
!I
II
,.I-tlO"''''
,
~jIII~c., r-C-~~ -.....c==OPjill,
'1.~ ~·l--c-4 I-c-,
•~ Ir"'""''''"'... ~
10
10
RIMAINDIR
I~0-.'("'... jill
I.-"'r'I tlO__ ~
.,
......c ......
--I.'~ ~\.c
/ ~,
r"+!f-----or" ~ ,,~----PII ...
::t~..o"'''' f -~- f--I'10"''''-~C
..I.......NOIR, ""''''"'..._ 'I"''''"'... ~~
!~
H----lr-:--:-:--------J.-t--::=--------;!'%H
ip
1-+----l~H----~~--¥f-i-----~---~~
!ia
*=a
IXT.lll011-DI:-CLIAIts.....N-l,,-~rCLIAIt '''AN'''.r--
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t." INTllllOIISU..f"OI'T....t~llCfI"lOItSU..I"OItT--t
INOSLA.CONTI,,"MVI ICONtlNUITY ....OVOIO. CliOSLA.COHflNUI""
BarLengthfmmFac«ofSlqIport
MinimumLength MuimumLenath
Mark a b c d e J g
Length 0.14/, 0.201. 0.22I. 0.30 I. 0.33/. 0.201. 0.24/.
•BentbanatcllccriorsupportsmaybeusedifapneraIanalyaisisniIde.
NOTS.....Dis!hediamecerofCbccolumnandthedi.'IICI\SionofCbcrcetanpllrcolUlllDinthedinodon...
COIlIiderltion.
FlO.16MlNlMUMBENDJOINTLOCAll0NSANDEXTENSIONSPORRmNFoRCBMENT
INFLATSLABS
60
31.7.4AnchoringReinforcement
a) All slabreinforcementperpendicularto a
discontinuous edge shall have an anchorage
(straight, bent or otherwise anchored) past the
internal face of the spandrel beam. wall or
column, of
anamount:
1) Forpositivereirforcement- not less than
150
mmexcept that with fabricreinforce
ment
havingafullyweldedtransversewire
directlyoverthesupport,
itshallbe
permissibleto reducethis lengthto one-half
of the
widthof the support or
SOmm,
whichever
isgreater; and
2)For
negativereinforcement-such that the
design
stressis developedat theinternal
face, in accordance with Section 3.
b)
Wherethe slabisnot supported by a spandrel
beamorwall, or wheretheslab cantilevers
beyond the support. the anchorage shall
be
obtained within the slab.
31.8OpeningsIn FlatSlabs
Openings of any size may be providedin the flat slab
ifit is shown by analysis that the requirements of
strength and serviceability are met. However, for
openings conforming to the following. no special
analysis
isrequired.
a) Openings of any size
maybe placed within the
middle half of the span in eachdirection.
provided the total amount of reinforcement
required for the panel without the opening is
maintained.
b) In the area
commonto two column strips, not
more than one-eighth of the width of strip
in
either span shall
beinterruptedby theopenings.
The equivalent of reinforcement interrupted
shall
beadded on all sides of the openings.
c) In theareacommonto onecolumnstripandone
middle strip,
notmore than one-quarterof the
reinforcementin eitherstripshallbeinterrupted
by theopenings.Theequivalentof rein
forcementinterruptedshall
beaddedonallsides
of the openings.
d) Theshearrequirementsof
31.6shallbesatisfied.
32WALLS
31.1General
Reinforcedconcretewallssubjectedtodirect
compressionorcombinedflexureanddirect
compression shouldbedesigned in accordance with
Section5orAnnexBprovidedthevertical
reinforcementis provided in each face. Braced walls
subjectedto
onlyverticalcompressionmaybedesigned
IS
456:2000
asperempiricalproceduregivenin31.2.Theminimum
thicknessof walls shall be 100rom.
32.1.1 Guidelines or design of walls subjected to
horizontaland verticalloads are given in 32.3.
32.2EmpiricalDesllllMethodforWallsSubjected
toInplaneVerticalLoads
32.2.1BracedWalls
Wallsshallbeassumedtobebracediftheyarelaterally
supported by a structure in which all the following
apply:
a)
Wallsor vertical braced elements are arranged
in twodirectionssoas toprovidelateralstability
to the structure as a whole.
h) Lateralforcesare resistedby shearin the planes
of thesewalls orbybracedelements.
c)Floorandroofsystemsaredesignedto transfer
lateralforces.
d) Connections between the wall and the lateral
supportsaredesignedto resistahorizontalforce
not
less than
1) thesimplestaticreactionsto thetotalapplied
horizontalforces at the level of lateral
support;and
2) 2.5 percentof the total verticalload
thatthe
wallisdesignedto
CaJTyatthelevelof lateral
support.
32.1.2Eccentricityo/Vertical Load
The design of awanshall take account of the actual
eccentricityof the verticalforcesubjectto a minimum
value ofO.OSt.
Theverticalloadtransmittedto a wall bya
discontinuous
concretefloor or roofshallbeassumed
to act at one-third the depth of the bearing area
measuredfromthe span face of the wall. Wherethere
is an
in-situconcrete floor continuous over the wall,
the load shall
beassumed to act at the centre of the
wall.
Theresultanteccentricity ofthetotal verticalload on
a bracedwallatany level between horizontal lateral
supports,shall be calculated on theassumptionthat
theresultanteccentricityof all the verticalloadsabove
the uppersupport is zero.
32.2.3Max;mrlmEffectiv«HeighttoThicknessRatio
The ratio of effective height tothickness.Hweltshall
notexceed 30.
31.2.4EffectiveHeight
The effectiveheightof a bracedwall shall be taken as
follows:
a)Where restrained against rotation at both ends
by
61
a) All slabreinforcementperpendicularto a
discontinuous edge shall have an anchorage
(straight, bent or otherwise anchored) past the
internal face of the spandrel beam. wall or
column, of
anamount:
1) Forpositivereirforcement- not less than
150
mmexcept that with fabricreinforce
ment
havingafullyweldedtransversewire
directlyoverthesupport,
itshallbe
permissibleto reducethis lengthto one-half
of the
widthof the support or
SOmm,
whichever
isgreater; and
2)For
negativereinforcement-such that the
design
stressis developedat theinternal
face, in accordance with Section 3.
b)
Wherethe slabisnot supported by a spandrel
beamorwall, or wheretheslab cantilevers
beyond the support. the anchorage shall
be
obtained within the slab.
31.8OpeningsIn FlatSlabs
Openings of any size may be providedin the flat slab
ifit is shown by analysis that the requirements of
strength and serviceability are met. However, for
openings conforming to the following. no special
analysis
isrequired.
a) Openings of any size
maybe placed within the
middle half of the span in eachdirection.
provided the total amount of reinforcement
required for the panel without the opening is
maintained.
b) In the area
commonto two column strips, not
more than one-eighth of the width of strip
in
either span shall
beinterruptedby theopenings.
The equivalent of reinforcement interrupted
shall
beadded on all sides of the openings.
c) In theareacommonto onecolumnstripandone
middle strip,
notmore than one-quarterof the
reinforcementin eitherstripshallbeinterrupted
by theopenings.Theequivalentof rein
forcementinterruptedshall
beaddedonallsides
of the openings.
d) Theshearrequirementsof
31.6shallbesatisfied.
32WALLS
31.1General
Reinforcedconcretewallssubjectedtodirect
compressionorcombinedflexureanddirect
compression shouldbedesigned in accordance with
Section5orAnnexBprovidedthevertical
reinforcementis provided in each face. Braced walls
subjectedto
onlyverticalcompressionmaybedesigned
IS
456:2000
asperempiricalproceduregivenin31.2.Theminimum
thicknessof walls shall be 100rom.
32.1.1 Guidelines or design of walls subjected to
horizontaland verticalloads are given in 32.3.
32.2EmpiricalDesllllMethodforWallsSubjected
toInplaneVerticalLoads
32.2.1BracedWalls
Wallsshallbeassumedtobebracediftheyarelaterally
supported by a structure in which all the following
apply:
a)
Wallsor vertical braced elements are arranged
in twodirectionssoas toprovidelateralstability
to the structure as a whole.
h) Lateralforcesare resistedby shearin the planes
of thesewalls orbybracedelements.
c)Floorandroofsystemsaredesignedto transfer
lateralforces.
d) Connections between the wall and the lateral
supportsaredesignedto resistahorizontalforce
not
less than
1) thesimplestaticreactionsto thetotalapplied
horizontalforces at the level of lateral
support;and
2) 2.5 percentof the total verticalload
thatthe
wallisdesignedto
CaJTyatthelevelof lateral
support.
32.1.2Eccentricityo/Vertical Load
The design of awanshall take account of the actual
eccentricityof the verticalforcesubjectto a minimum
value ofO.OSt.
Theverticalloadtransmittedto a wall bya
discontinuous
concretefloor or roofshallbeassumed
to act at one-third the depth of the bearing area
measuredfromthe span face of the wall. Wherethere
is an
in-situconcrete floor continuous over the wall,
the load shall
beassumed to act at the centre of the
wall.
Theresultanteccentricity ofthetotal verticalload on
a bracedwallatany level between horizontal lateral
supports,shall be calculated on theassumptionthat
theresultanteccentricityof all the verticalloadsabove
the uppersupport is zero.
32.2.3Max;mrlmEffectiv«HeighttoThicknessRatio
The ratio of effective height tothickness.Hweltshall
notexceed 30.
31.2.4EffectiveHeight
The effectiveheightof a bracedwall shall be taken as
follows:
a)Where restrained against rotation at both ends
by
61
IS456:2000
32.~~WallsSubjectedtoCombinedHorizontal
andVerticalForces
2)intersectingwalls or 1.0 L
1
similar members
whichever is the lesser.
where
P
wis determined asfollows:
a) For walls whereH
w
'Ly,:S1.P
w
shall be the
Jesserof the ratios ofeitherthevertical
reinforcementareaor thehorizontal
reinforcementareato thecross-sectional area
ofwall in the respective direction.
b) For walls whereHwIL
w
>1,PVishallhethe
ratio of thehorizontalreinforcementarea to
the cross-sectional
areaof wall per vertical
metre.
.....(H.v /I..:
~J )
i.
r w
z:.1(.,",::r\:.:-----,---.~----.- ..-.
.....(/-'\"/1.....,_..,)
whereK,~,p.n4~inJir"it"f~~tt' n\(~1hodand
0.03inworkincst.rt~~.;smethod.but shallbe
notlessthanK~ ,\;~T~'inallYv.r-c. whereK,
isf),l.t;inlinutstate rnethodand0.)0 in
workingstressmethod.
~~2..4.4.DesignoJ'ShearReiniorcemcnt
Shear reinforcementshallhe providedto carryashear
equal toV
l
-"'\;w.t(OJ~L....).'Incase of workingstress
methodV
l1
is replacedbyV.Thestrengthofshear
reinforcement shall be calculatedd~per 40.4 orB~S.4
withA""definedasbelow:
A
oI
\,=P
w(0.8 L
w
)
t
32.5MinimumRequirementsfor
Reinforcement
in Walls
The reinforcementfor wallsshallbe providedas below:
b)ForI(./L
w
>J
Lesserofthe ·~';·dlJf:~~ L'cl]c'Jlafcdfrom(a')
above
and.I'ro'lJ
where
32.4.3DesignShearStrengthof'Concrete
Thedesignshearstrengthofconcreteinwalls,
t
n v
'withoutshearreinforcementshallbe taken as
below:
a) ForH
w
ILw~1
t(.w=(3,0-Il
w
/L
w
)K,K
whereK
1
is0.2 inlimitstatemethodand0.13
in
workingstressmethod.
~I=shearforceduetodesign loads.
=wallthickness.
d=n.R><L~whereL",isthelength of
thewall
32.4.2..]rJndc,nocircumstancesshall thenominal
shearstressrvwm wallsexceed0.17t;inlimitstate
methodand012/.
l
inworking stressmethod.
1.0
II
or
ow
0.75/1or
w
0.75[J)
J)floors
2)
intersectingwalls or
similar members
whichever is the lesser.h)Where notrestrainedagainst rotation at hoth
ends
by
I)floors
32.3.1 When horizontal forces are in the plane of the
wall.
itmaybedesignedforvertical
forcesin
accordancewith32.2andforhorizontalshear in
accordancewith32.3.Inplanebendingmaybe
neglected in case a horizontal cross
..section of the wall
is always under compression due to combined effect
of horizontal and vertical loads.
32.3.2Wallssubjectedtohorizontalforces
perpendicular to the wall
andfor which thedesignaxial
loaddoesnotexceed0.04.f~kAi'shall bedesignedas
slabs in accordance with the appropriate provisions
under 24, where A isgrossarea of the section.
it
32.4DesignforHorizontalShear
32.4.1CriticalSection/orShear
The critical sectionformaximum shearshallbe taken
at a distance from the base ofO.SL
w
or 0.5H..,
whichever is less.
32.4.2 Nominal Shear Stress
The nominalshearstresst\lWin wallsshallbeobtained
as follows:
r =V/t.d
yw u
II\Ii:;:;theunsupportedheightof the wall,
L,=the horizontaldistancebetweencentres
oflateralrestraint.
32.2..5DesignAxialStrength.ofWall
111edesign axial strengthPu~per unitlengthof abraced
wall incompressionmay becalculatedfrom the
followingequation:
P
l 1W=0.3(t-1.2e-2e)fck
where
=thicknessof thewall,
e=eccentricityof load measured atTIght
angles to the planeofthe wall determined
in accordance with 32.2.2,and
e'l::additiona}eccentricity due toslen
dcrness effect taken as/-1I2 500t.
we'
62
32.~~WallsSubjectedtoCombinedHorizontal
andVerticalForces
2)intersectingwalls or 1.0 L
1
similar members
whichever is the lesser.
where
P
wis determined asfollows:
a) For walls whereH
w
'Ly,:S1.P
w
shall be the
Jesserof the ratios ofeitherthevertical
reinforcementareaor thehorizontal
reinforcementareato thecross-sectional area
ofwall in the respective direction.
b) For walls whereHwIL
w
>1,PVishallhethe
ratio of thehorizontalreinforcementarea to
the cross-sectional
areaof wall per vertical
metre.
.....(H.v /I..:
~J )
i.
r w
z:.1(.,",::r\:.:-----,---.~----.- ..-.
.....(/-'\"/1.....,_..,)
whereK,~,p.n4~inJir"it"f~~tt' n\(~1hodand
0.03inworkincst.rt~~.;smethod.but shallbe
notlessthanK~ ,\;~T~'inallYv.r-c. whereK,
isf),l.t;inlinutstate rnethodand0.)0 in
workingstressmethod.
~~2..4.4.DesignoJ'ShearReiniorcemcnt
Shear reinforcementshallhe providedto carryashear
equal toV
l
-"'\;w.t(OJ~L....).'Incase of workingstress
methodV
l1
is replacedbyV.Thestrengthofshear
reinforcement shall be calculatedd~per 40.4 orB~S.4
withA""definedasbelow:
A
oI
\,=P
w(0.8 L
w
)
t
32.5MinimumRequirementsfor
Reinforcement
in Walls
The reinforcementfor wallsshallbe providedas below:
b)ForI(./L
w
>J
Lesserofthe ·~';·dlJf:~~ L'cl]c'Jlafcdfrom(a')
above
and.I'ro'lJ
where
32.4.3DesignShearStrengthof'Concrete
Thedesignshearstrengthofconcreteinwalls,
t
n v
'withoutshearreinforcementshallbe taken as
below:
a) ForH
w
ILw~1
t(.w=(3,0-Il
w
/L
w
)K,K
whereK
1
is0.2 inlimitstatemethodand0.13
in
workingstressmethod.
~I=shearforceduetodesign loads.
=wallthickness.
d=n.R><L~whereL",isthelength of
thewall
32.4.2..]rJndc,nocircumstancesshall thenominal
shearstressrvwm wallsexceed0.17t;inlimitstate
methodand012/.
l
inworking stressmethod.
1.0
II
or
ow
0.75/1or
w
0.75[J)
J)floors
2)
intersectingwalls or
similar members
whichever is the lesser.h)Where notrestrainedagainst rotation at hoth
ends
by
I)floors
32.3.1 When horizontal forces are in the plane of the
wall.
itmaybedesignedforvertical
forcesin
accordancewith32.2andforhorizontalshear in
accordancewith32.3.Inplanebendingmaybe
neglected in case a horizontal cross
..section of the wall
is always under compression due to combined effect
of horizontal and vertical loads.
32.3.2Wallssubjectedtohorizontalforces
perpendicular to the wall
andfor which thedesignaxial
loaddoesnotexceed0.04.f~kAi'shall bedesignedas
slabs in accordance with the appropriate provisions
under 24, where A isgrossarea of the section.
it
32.4DesignforHorizontalShear
32.4.1CriticalSection/orShear
The critical sectionformaximum shearshallbe taken
at a distance from the base ofO.SL
w
or 0.5H..,
whichever is less.
32.4.2 Nominal Shear Stress
The nominalshearstresst\lWin wallsshallbeobtained
as follows:
r =V/t.d
yw u
II\Ii:;:;theunsupportedheightof the wall,
L,=the horizontaldistancebetweencentres
oflateralrestraint.
32.2..5DesignAxialStrength.ofWall
111edesign axial strengthPu~per unitlengthof abraced
wall incompressionmay becalculatedfrom the
followingequation:
P
l 1W=0.3(t-1.2e-2e)fck
where
=thicknessof thewall,
e=eccentricityof load measured atTIght
angles to the planeofthe wall determined
in accordance with 32.2.2,and
e'l::additiona}eccentricity due toslen
dcrness effect taken as/-1I2 500t.
we'
62
a) theminimumratio of verticalreinforcementto
grossconcretearea shall be:
1)0.001 2 fordeformedbars not larger than
16 mm indiameterand with acharacteristic
strength
of41
5N/mm
2
or greater.
2) 0.001 5 for other types of bars.
3) 0.(:)12 for welded wire fabric not larger than
16 mm in diameter,
b)Vertical
reinforcementshallbe
spacednot
farther apart than three times the wall thickness
nor450mm.
c)Theminimumratio ofhorizontalreinforcement
to grossconcretearea shalt be:
1) 0.002 0 fordeformedbars not larger than
16 mm indiameterand with acharacteristic
strengthof 415
Nzmm'or greater.
2)
0.0025for other types of bars.
3) 0.002 () for welded wire fabric not larger
than 16 rntn in diameter.
d)Horizontalreinforcementshalt
bespaced not
farther apart than three times the wallthickness
nor 450 mm.
NOTE _.'.
Theminimumremforcement may not alwaysbe
sufficienttoprovideadequateresrsrancetotheeffectsof
shrinkageandtemperature
32.5.1 For walls having thickness more than 200 mm,
theverticalandhorizontalreinforcementshall
beprovidedin two grids, oneneareachfaceof the
wall.
32.5.2Verticalreinforcementneed not heenclosed
by
transversereinforcementas given in26.5.3.2for
column.if theverticalreinforcementis notgreater
than 0.0 I times the grosssectionalarea or where the
verticalreinforcementisnotrequiredfor
compression,
33
STAIRS
33.1
EffectiveSpanofStairs
The effectivespanof stairs without stringer heams shall
I
I 1K
I
I
I
II
~ ~
,
I
UPi
•It-
~x-•x4-GOING(G)---+'v-i-v-l
IS456:2000
be taken asthefollowing horizontaldistances:
a) Where supported at top and bottom risers by
beamsspanning parallelwith therisers.the
distancecentre-to-centreof beams;
b) Where spanning on to the edge of a landing slab.
which spans parallel, with the risers
(seeFig.
17). adistanceequal to the going
ofthe stairs
plus at each endeitherhalf the width
ofthe
landing or one metre.whicheveris smaller; and
c)
Wherethelanding slabspansin the same
directionas the stairs. they shallbeconsidered
as actingtogetherto form a single slab and the
span determined as the distancecentre-to-centre
of the supporting beams or walls. the going being
measuredhorizontally.
33.2DistributionofLoadingon
Stairs
In the case of stairs with open wells, where spans partly
crossingatrightanglesoccur,the load onareas
common to any two such spans may be taken as one
half in each directiona~shown in Fig. 18.Where flights
or landings areembeddedinto walls for a length
of
norless than I10 mm and aredesignedto span in the
direction of the flight. a 150 mm strip may bededucted
from the loaded area and the effectivebreadthof
the
section increased by75 mm for purposes of design(see
Fig. 19).
33.3
DepthofSection
111edepth of section shalt
betaken as theminimum
thicknessperpendicularto the soffit of the staircase.
34
FOOTIN(;S
34.1General
Footings shall be designed
tosustain the applied loads.
moments andforcesand the inducedreactionsandto
ensure that anysettlementwhich mayoccurshall be
as nearly uniform as possible. and the safe bearing
capacity
ofthe soil is notexceeded
(saIS 1904).
34.1.1 Inslopedorsteppedfootings theeffective
x
y
SPAN INMETRES
<1m<1m G·X·Y
<1m>'m G.X+1
>'m<1m G·Y·'
>lm>'m
G.,+1
,---.
FIG.17EFfECTIVr-:SPAN FOR STAIRS SUPPORTED AT EACH END IW
LANDINGSSPANNINGPARALLELWnHTHERISERS
63
grossconcretearea shall be:
1)0.001 2 fordeformedbars not larger than
16 mm indiameterand with acharacteristic
strength
of41
5N/mm
2
or greater.
2) 0.001 5 for other types of bars.
3) 0.(:)12 for welded wire fabric not larger than
16 mm in diameter,
b)Vertical
reinforcementshallbe
spacednot
farther apart than three times the wall thickness
nor450mm.
c)Theminimumratio ofhorizontalreinforcement
to grossconcretearea shalt be:
1) 0.002 0 fordeformedbars not larger than
16 mm indiameterand with acharacteristic
strengthof 415
Nzmm'or greater.
2)
0.0025for other types of bars.
3) 0.002 () for welded wire fabric not larger
than 16 rntn in diameter.
d)Horizontalreinforcementshalt
bespaced not
farther apart than three times the wallthickness
nor 450 mm.
NOTE _.'.
Theminimumremforcement may not alwaysbe
sufficienttoprovideadequateresrsrancetotheeffectsof
shrinkageandtemperature
32.5.1 For walls having thickness more than 200 mm,
theverticalandhorizontalreinforcementshall
beprovidedin two grids, oneneareachfaceof the
wall.
32.5.2Verticalreinforcementneed not heenclosed
by
transversereinforcementas given in26.5.3.2for
column.if theverticalreinforcementis notgreater
than 0.0 I times the grosssectionalarea or where the
verticalreinforcementisnotrequiredfor
compression,
33
STAIRS
33.1
EffectiveSpanofStairs
The effectivespanof stairs without stringer heams shall
I
I 1K
I
I
I
II
~ ~
,
I
UPi
•It-
~x-•x4-GOING(G)---+'v-i-v-l
IS456:2000
be taken asthefollowing horizontaldistances:
a) Where supported at top and bottom risers by
beamsspanning parallelwith therisers.the
distancecentre-to-centreof beams;
b) Where spanning on to the edge of a landing slab.
which spans parallel, with the risers
(seeFig.
17). adistanceequal to the going
ofthe stairs
plus at each endeitherhalf the width
ofthe
landing or one metre.whicheveris smaller; and
c)
Wherethelanding slabspansin the same
directionas the stairs. they shallbeconsidered
as actingtogetherto form a single slab and the
span determined as the distancecentre-to-centre
of the supporting beams or walls. the going being
measuredhorizontally.
33.2DistributionofLoadingon
Stairs
In the case of stairs with open wells, where spans partly
crossingatrightanglesoccur,the load onareas
common to any two such spans may be taken as one
half in each directiona~shown in Fig. 18.Where flights
or landings areembeddedinto walls for a length
of
norless than I10 mm and aredesignedto span in the
direction of the flight. a 150 mm strip may bededucted
from the loaded area and the effectivebreadthof
the
section increased by75 mm for purposes of design(see
Fig. 19).
33.3
DepthofSection
111edepth of section shalt
betaken as theminimum
thicknessperpendicularto the soffit of the staircase.
34
FOOTIN(;S
34.1General
Footings shall be designed
tosustain the applied loads.
moments andforcesand the inducedreactionsandto
ensure that anysettlementwhich mayoccurshall be
as nearly uniform as possible. and the safe bearing
capacity
ofthe soil is notexceeded
(saIS 1904).
34.1.1 Inslopedorsteppedfootings theeffective
x
y
SPAN INMETRES
<1m<1m G·X·Y
<1m>'m G.X+1
>'m<1m G·Y·'
>lm>'m
G.,+1
,---.
FIG.17EFfECTIVr-:SPAN FOR STAIRS SUPPORTED AT EACH END IW
LANDINGSSPANNINGPARALLELWnHTHERISERS
63
IS456:2000
w
THELOADONARE
COMMON TOTWO
SYSTEMS TO81£
TAKENASONE
HAL,.INEACH
DIRECTION
.c
8 E A M
I
!
I
I~N
,
I
UP
Flo.18LoADINOONSTAIRSWITHOPENWELLS FlO.19LoADINOONSTAIRS
Bun.TINTOWAJ,.LS
cross-sectionincompressionshall belimitedbytho
areaabovetheneutralplane,andthoangleof slopeor
depthandlocationofstepsshallbesuchthatthedesip
requirementsaresatisfiedateverysection.Slopedand
steppedfootingsthataredesignedas a unit shall be
constructedto
assureactionas aunit.
34.1.2ThicknessattheEdge01Footing
Inreinforcedandplainconcretefootings,thethickness
at theedgeshallbenotlessthan150mmforfootings
onsoils,norlessthan300mmabovethetopsofpiles
forfootingsonpiles.
34.1.3Inthecaseofplainconcretepedestals,theangle
betweentheplanepassingthroughthebottomedgeof
the
pedestaland thecorrespondingjunction
edgeof
the column withpedestaland thehorizontalplane
(seeFig.20)shallbegovernedby theexpression:
tana~0.9pooq"+1
I..
where
q"•calculatedmaximumbearingpressureat
thebaseafthepedestalinN/mm
2
,
and
leII.=characteristicstren,thof concrete at
28 daysin
N/mm
2
•
34.2MomenbandFore.
34.1.11nthe case offootingsonpiles,computation
for moments and shears may be based on the
assumptionthat thereactionfrom any pile is
concentratedat thecentreof thepile.
34.2.2Forthepurposeofcomputin,stressesinfootings
whichsupportaroundoroctagonalconcretecolumnor
pedestal,thefaceofthecolumnorpedestalshallbe
taken as the side of a square inscribed within the
perimeteroftheroundoroctagonalcolumnorpedestal.
34.2.3BendingMoment
34.2.3.1Thebendingmomentat anysectionshall be
determinedbypassingthroughthesectionavertical
I
I
COLUMN
PLAIN
CONCRETE
PEDESTAL
Flo.20
64
w
THELOADONARE
COMMON TOTWO
SYSTEMS TO81£
TAKENASONE
HAL,.INEACH
DIRECTION
.c
8 E A M
I
!
I
I~N
,
I
UP
Flo.18LoADINOONSTAIRSWITHOPENWELLS FlO.19LoADINOONSTAIRS
Bun.TINTOWAJ,.LS
cross-sectionincompressionshall belimitedbytho
areaabovetheneutralplane,andthoangleof slopeor
depthandlocationofstepsshallbesuchthatthedesip
requirementsaresatisfiedateverysection.Slopedand
steppedfootingsthataredesignedas a unit shall be
constructedto
assureactionas aunit.
34.1.2ThicknessattheEdge01Footing
Inreinforcedandplainconcretefootings,thethickness
at theedgeshallbenotlessthan150mmforfootings
onsoils,norlessthan300mmabovethetopsofpiles
forfootingsonpiles.
34.1.3Inthecaseofplainconcretepedestals,theangle
betweentheplanepassingthroughthebottomedgeof
the
pedestaland thecorrespondingjunction
edgeof
the column withpedestaland thehorizontalplane
(seeFig.20)shallbegovernedby theexpression:
tana~0.9pooq"+1
I..
where
q"•calculatedmaximumbearingpressureat
thebaseafthepedestalinN/mm
2
,
and
leII.=characteristicstren,thof concrete at
28 daysin
N/mm
2
•
34.2MomenbandFore.
34.1.11nthe case offootingsonpiles,computation
for moments and shears may be based on the
assumptionthat thereactionfrom any pile is
concentratedat thecentreof thepile.
34.2.2Forthepurposeofcomputin,stressesinfootings
whichsupportaroundoroctagonalconcretecolumnor
pedestal,thefaceofthecolumnorpedestalshallbe
taken as the side of a square inscribed within the
perimeteroftheroundoroctagonalcolumnorpedestal.
34.2.3BendingMoment
34.2.3.1Thebendingmomentat anysectionshall be
determinedbypassingthroughthesectionavertical
I
I
COLUMN
PLAIN
CONCRETE
PEDESTAL
Flo.20
64
where
AI=
plane whichextendscompletelyacrossthefooting,and
computing the moment of the forces acting over the
entire area of the footing on one side of the said plane.
34.2.3.2The greatest bending moment to be used in
thedesignof anisolatedconcretefooting which
supportsacolumn.pedestal
orwall, shall be the
momentcomputedin the mannerprescribedin
34.2.3.1
at sections located as follows:
a) At the face of the column, pedestal or wall, for
footings supporting a concrete column, pedestal
or
wall;
b) Halfway between the centre-line and the edge
of the wall, for footings under masonry walls;
and
c) Halfway between the face of the column or
pedestal and the edge of the gussetted base, for
footings under gussetted bases.
34.2.4Shear and Bond
34.2.4.1 The shear strength of footings is governed by
the more severe of the following two conditions:
a) The footing acting essentially as a wide beam,
with apotential diagonalcrackextendingin a
plane across the entire width; the criticalsection
for this condition shall be assumed as a vertical
section located from the face of the column,
pedestalor wall at adistanceequal to the
effective depth of footing for footings on piles.
b)Two-way actionofthe footing, with potential
diagonal cracking along the surfaceof
truncated
coneorpyramid around the concentrated load;
in this case, the footing shall be designed for
shear in accordance with appropriateprovisions
specified in 31.6.
34.2.4.2In computingtheexternalshearoranysection
througha footingsupportedon piles,theentirereaction
from any pile of diameter
D
(1whose centre is located
D /2 or more outside the section shall be
assumedas
p:oducing shear on the section; the reaction from any
pile whose centre is located
Dr/2 or more inside the
section shall be assumed as producing no shear on the
section. For intermediate positions of the pile centre,
the portion of the pile reaction to be assumed as
producingshear
onthe section shall be based on
straight line interpolation between full value at D
(1/2
outside the section and zero value atD/2 inside the
I'
section.
34.2.4.3Thecriticalsectionforcheckingthe
development length in a footing shall
beassumed at
the sameplanes as thosedescribedforbendingmoment
in
34.2.3and also at all other vertical planes where
abrupt changes of section occur. If reinforcement is
curtailed, the anchorage requirementsshall
bechecked
in accordance with
26.2.3.
2116815/07-10
IS456:2000
34.3 TensileReinforcement
The total tensile reinforcement at any section shall
provide a moment of resistance at least equal to the
bendingmomenton the
sectioncalculatedin
accordance with 34.2.3.
34.3.1Totaltensile reinforcementshallbedistributed
across the corresponding resisting section as given
below:
a) In one-wayreinforcedfooting,thereinforcement
extending
ineach direction shallbedistributed
uniformly across the full width of the footing;
h) In two-wayreinforcedsquarefooting,the
reinforcementextending in each direction shall
be distributed
uniformlyacross thefullwidth
ofthe footing; and
c) In two-way reinforced rectangular
footing.the
reinforcementin the long direction shall be
distributed unifonnly across the full width of
the footing. Forreinforcementin the short
direction, a central band equal to the width of
the footing shall
bemarked along the length of
the footing and portion of the reinforcement
determined in accordance with the equation
given below shall be uniformlydistributed
across
thecentralband:
Reinforcement in central band width 2
Total reinforcement in short direction
=
~+ 1
where~is the ratio of the long side to the short
sideofthefooting.Theremainderofthe
reinforcement shall be uniformly distributed in
the outer portions of the footing.
34.4Transferof LoadattheBase ofColumn
Thecompressivestress inconcreteat thebaseofa
column orpedestalshallbeconsideredas being
transferred
bybearing to the top of the supporting
pedestalor
footing.The bearingpressureon the loaded
area shall not exceed the permissible bearing stress in
direct cornpression multiplied by a value equal to
Kbut not greater than 2;
~A;
supporting area for bearing of footing,
which in sloped or .stepped footing
may
be
takenas the area of the lower base of
the largest
frustumof apyramidor cone
contained wholly within the footing and
havingfor its upper
base,thearea actually
loaded andhavingside slope of one
verticalto two horizontal; and
A
2=loaded area at the column base.
65
AI=
plane whichextendscompletelyacrossthefooting,and
computing the moment of the forces acting over the
entire area of the footing on one side of the said plane.
34.2.3.2The greatest bending moment to be used in
thedesignof anisolatedconcretefooting which
supportsacolumn.pedestal
orwall, shall be the
momentcomputedin the mannerprescribedin
34.2.3.1
at sections located as follows:
a) At the face of the column, pedestal or wall, for
footings supporting a concrete column, pedestal
or
wall;
b) Halfway between the centre-line and the edge
of the wall, for footings under masonry walls;
and
c) Halfway between the face of the column or
pedestal and the edge of the gussetted base, for
footings under gussetted bases.
34.2.4Shear and Bond
34.2.4.1 The shear strength of footings is governed by
the more severe of the following two conditions:
a) The footing acting essentially as a wide beam,
with apotential diagonalcrackextendingin a
plane across the entire width; the criticalsection
for this condition shall be assumed as a vertical
section located from the face of the column,
pedestalor wall at adistanceequal to the
effective depth of footing for footings on piles.
b)Two-way actionofthe footing, with potential
diagonal cracking along the surfaceof
truncated
coneorpyramid around the concentrated load;
in this case, the footing shall be designed for
shear in accordance with appropriateprovisions
specified in 31.6.
34.2.4.2In computingtheexternalshearoranysection
througha footingsupportedon piles,theentirereaction
from any pile of diameter
D
(1whose centre is located
D /2 or more outside the section shall be
assumedas
p:oducing shear on the section; the reaction from any
pile whose centre is located
Dr/2 or more inside the
section shall be assumed as producing no shear on the
section. For intermediate positions of the pile centre,
the portion of the pile reaction to be assumed as
producingshear
onthe section shall be based on
straight line interpolation between full value at D
(1/2
outside the section and zero value atD/2 inside the
I'
section.
34.2.4.3Thecriticalsectionforcheckingthe
development length in a footing shall
beassumed at
the sameplanes as thosedescribedforbendingmoment
in
34.2.3and also at all other vertical planes where
abrupt changes of section occur. If reinforcement is
curtailed, the anchorage requirementsshall
bechecked
in accordance with
26.2.3.
2116815/07-10
IS456:2000
34.3 TensileReinforcement
The total tensile reinforcement at any section shall
provide a moment of resistance at least equal to the
bendingmomenton the
sectioncalculatedin
accordance with 34.2.3.
34.3.1Totaltensile reinforcementshallbedistributed
across the corresponding resisting section as given
below:
a) In one-wayreinforcedfooting,thereinforcement
extending
ineach direction shallbedistributed
uniformly across the full width of the footing;
h) In two-wayreinforcedsquarefooting,the
reinforcementextending in each direction shall
be distributed
uniformlyacross thefullwidth
ofthe footing; and
c) In two-way reinforced rectangular
footing.the
reinforcementin the long direction shall be
distributed unifonnly across the full width of
the footing. Forreinforcementin the short
direction, a central band equal to the width of
the footing shall
bemarked along the length of
the footing and portion of the reinforcement
determined in accordance with the equation
given below shall be uniformlydistributed
across
thecentralband:
Reinforcement in central band width 2
Total reinforcement in short direction
=
~+ 1
where~is the ratio of the long side to the short
sideofthefooting.Theremainderofthe
reinforcement shall be uniformly distributed in
the outer portions of the footing.
34.4Transferof LoadattheBase ofColumn
Thecompressivestress inconcreteat thebaseofa
column orpedestalshallbeconsideredas being
transferred
bybearing to the top of the supporting
pedestalor
footing.The bearingpressureon the loaded
area shall not exceed the permissible bearing stress in
direct cornpression multiplied by a value equal to
Kbut not greater than 2;
~A;
supporting area for bearing of footing,
which in sloped or .stepped footing
may
be
takenas the area of the lower base of
the largest
frustumof apyramidor cone
contained wholly within the footing and
havingfor its upper
base,thearea actually
loaded andhavingside slope of one
verticalto two horizontal; and
A
2=loaded area at the column base.
65
IS456:2000
For working stress method of design thepermissible
bearingstresson fullareaof concreteshall betakenas
0.25!c,,;forlimitstatemethodofdesignthepermissible
bearing
stress shall be 0.45
let.
34.4.1Wherethepermissible bearing stress on the
concretein thesupportingorsupportedmemberwould
be exceeded, reinforcement shall be provided for
developing the excess force, either by extending the
longitudinalbars into thesupporting
member,or by
dowels
(see34.4.3).
34.4.2Where transfer of force isaccomplishedby
reinforcement,thedevelopmentlengthof the
reinforcementshall besufficienttotransferthe
compression or tension to the supportingmember in
accordancewith26.2.
34.4.3Extendedlongitudinalreinforcementordowels
of at leastO.Spercentof thecross-sectionalareaof the
supportedcolumn or pedestaland aminimum
offour
bars shall beprovided.Where dowels are used, their
diameter shall no exceed the diameter of the column
bars
bymore than 3 mm,
34.4.4 Column bars of diameters larger than 36 mm,
incompressiononly can be dowelled at the footings
with bars of smaller size of the necessary area. The
dowel shall extend into the column. a distance equal
to thedevelopmentlengthof the column bar and into
the
footing,adistanceequaltothedevelopmentlength
ofthe dowel.
34.5Nominal Reinforcement
34.5.1Minimumreinforcementand spacing shall be
as per therequirementsof solid slab.
34.5.2The nominalreinforcementforconcrete
sections
of thickness greater than 1 m shall be
360mm
z
permetrelengthineach direction on each
face.Thisprovisiondoesnotsupersedetherequirement
of minimumtensilereinforcementbasedon the depth
of the section.
For working stress method of design thepermissible
bearingstresson fullareaof concreteshall betakenas
0.25!c,,;forlimitstatemethodofdesignthepermissible
bearing
stress shall be 0.45
let.
34.4.1Wherethepermissible bearing stress on the
concretein thesupportingorsupportedmemberwould
be exceeded, reinforcement shall be provided for
developing the excess force, either by extending the
longitudinalbars into thesupporting
member,or by
dowels
(see34.4.3).
34.4.2Where transfer of force isaccomplishedby
reinforcement,thedevelopmentlengthof the
reinforcementshall besufficienttotransferthe
compression or tension to the supportingmember in
accordancewith26.2.
34.4.3Extendedlongitudinalreinforcementordowels
of at leastO.Spercentof thecross-sectionalareaof the
supportedcolumn or pedestaland aminimum
offour
bars shall beprovided.Where dowels are used, their
diameter shall no exceed the diameter of the column
bars
bymore than 3 mm,
34.4.4 Column bars of diameters larger than 36 mm,
incompressiononly can be dowelled at the footings
with bars of smaller size of the necessary area. The
dowel shall extend into the column. a distance equal
to thedevelopmentlengthof the column bar and into
the
footing,adistanceequaltothedevelopmentlength
ofthe dowel.
34.5Nominal Reinforcement
34.5.1Minimumreinforcementand spacing shall be
as per therequirementsof solid slab.
34.5.2The nominalreinforcementforconcrete
sections
of thickness greater than 1 m shall be
360mm
z
permetrelengthineach direction on each
face.Thisprovisiondoesnotsupersedetherequirement
of minimumtensilereinforcementbasedon the depth
of the section.
IS456:ZOOO
SECTION5STRUCTURALDESIGN(LIMITSTATEMETHOD)
35SAFETYANDSERVICEABILITY
REQUIREMENTS
35.1General
In the method of design based on limit state concept,
the structure shall be designed to withstand
safelyall
loadsliable to act on it throughoutits life;
itshall also
satisfytheserviceabilityrequirements,such as
limitationson deflectionand cracking.The acceptable
limit for the safety and serviceability requirements
before failure occurs is called a 'limit state' . The aim
of design is to achieve acceptableprobabilitiesthat
the
structurewill notbecomeunfitfortheuseforwhich
itis intended,that is, thatitwill not reacha Iimitstate.
35.1.1 All relevant limit states shall
beconsideredin
design to ensure an adequate degree of safety and
serviceability.
Ingeneral,thestructureshall be
designed on the
basisofthe most critical limit state
and shall be checked for other limit states.
35.1.2Forensuring theaboveobjective, the design
should be based on characteristic values for material
strengths and appliedloads,which take into account
the variationsin the materialstrengthsand in theloads
to
besupported.Thecharacteristic values should be
based on statistical data
jfavailable: wheresuch data
are not available they should be based on experience.
The 'design values' arederivedfromthecharacteristic
values through the use of partial safety factors, one
for material strengths and the other for loads.
Inthe
absence
ofspecial considerationsthesefactorsshould
have the values given in 36 according to the material.
thetype
ofloading.and thelimitstatebeing
considered.
35.2Limit State 01CoDapse
The limit state of collapse of the structure or part of
the structure could
beassessedfrom ruptureof one or
morecritical sectionsand frombucklingdue toelastic
or plastic instability (including the effects of sway
where appropriate)
oroverturning.The resistance to
bending,shear,torsionand axialloadsat everysection
shall not be less than the appropriate value at that section produced by the probable mostunfavourable
combination
ofloads on thestructureusing the
appropriate partial safety factors.
35.3LimitStatesofServiceabUlty
35.3.1Deflection
Limiting values of deflectionsare given in23.2.
35.3.2Cracking
Cracking of concrete should notadverselyaffect the
appearanceordurabilityofthestructure;theacceptable
limitsofcrackingwouldvarywiththe typeof structure
andenvironment.Wherespecificattentionis required
to limit
thedesignedcrack widthto aparticularvalue.
crack width calculation
maybe done using formula
given in Annex
F.
Thepractical objective of calculatingcrackwidthis
merely to give guidance to the designer in making
appropriatestructuralarrangementsand in avoiding
grosserrorsindesign,whichmightresultin
concentrationand excessive widthof flexuralcrack.
The surfacewidthof the cracksshouldnot, in general,
exceed 0.3
mm inmembers where cracking is not
harmfuland does not have
anyseriousadverseeffects
uponthepreservationof reinforcing
steelnor uponthe
durabilityofthestructures.Inmemberswherecracking
in the tensile zoneisharmful either becausetheyare
exposed to the effects of the weatheror continuously exposedto moistureor incontactsoil or groundwater,
anupperlimitof0.2mmissuggestedforthe
maximum
widthofcracks.Forparticularlyaggressive
environment,such as the
'severe'category in Table3,
the assessed surface width of cracks should not in
general,exceed0.1 mm.
35.4OtherLimitStates
Structures designed forunusualorspecial functions
shall comply with
anyrelevant additional limit stale
consideredappropriateto that
structure.
36CHARACTERISTIC ANDDESIGN
VALUESANDPARTIALSAFETYFACTORS
36.1CharacteristicStrengthofMaterials
The term 'characteristicstrength' means that valueof
thestrengthofthematerialbelowwhichnotmorethan
5 percent of the test results are expected to fall. The
characteristicstrengthforconcreteshallbe in
accordance
withTable 2. Until the relevant Indian
StandardSpecificationsforreinforcingsteel are
modified to
includethe concept ofcharacteristic
strength, thecharacteristicvalue shall
beassumed as
the minimum yield stress
10.2percent proof stress
specifiedin
therelevantIndianStandardSpecifications.
36.2CharacteristicLoads
The tenn'characteristicload' meansthat valueof load
whichhasa9Spercentprobabilityof notbeingexceeded
during the life of the structure. Since dataarenot
availableto express loads instatisticalterms, for
the
purposeof this standard, dead loads given in IS 875
(Part 1).
imposedloadsgiven in IS 875 (Part
2),wind
loads given in IS 875 (Part 3), snow load as given in
IS 875 (Part 4) and seismic
forcesgiven in IS 1893
shall
beassumedas thecharacteristicloads.
61
SECTION5STRUCTURALDESIGN(LIMITSTATEMETHOD)
35SAFETYANDSERVICEABILITY
REQUIREMENTS
35.1General
In the method of design based on limit state concept,
the structure shall be designed to withstand
safelyall
loadsliable to act on it throughoutits life;
itshall also
satisfytheserviceabilityrequirements,such as
limitationson deflectionand cracking.The acceptable
limit for the safety and serviceability requirements
before failure occurs is called a 'limit state' . The aim
of design is to achieve acceptableprobabilitiesthat
the
structurewill notbecomeunfitfortheuseforwhich
itis intended,that is, thatitwill not reacha Iimitstate.
35.1.1 All relevant limit states shall
beconsideredin
design to ensure an adequate degree of safety and
serviceability.
Ingeneral,thestructureshall be
designed on the
basisofthe most critical limit state
and shall be checked for other limit states.
35.1.2Forensuring theaboveobjective, the design
should be based on characteristic values for material
strengths and appliedloads,which take into account
the variationsin the materialstrengthsand in theloads
to
besupported.Thecharacteristic values should be
based on statistical data
jfavailable: wheresuch data
are not available they should be based on experience.
The 'design values' arederivedfromthecharacteristic
values through the use of partial safety factors, one
for material strengths and the other for loads.
Inthe
absence
ofspecial considerationsthesefactorsshould
have the values given in 36 according to the material.
thetype
ofloading.and thelimitstatebeing
considered.
35.2Limit State 01CoDapse
The limit state of collapse of the structure or part of
the structure could
beassessedfrom ruptureof one or
morecritical sectionsand frombucklingdue toelastic
or plastic instability (including the effects of sway
where appropriate)
oroverturning.The resistance to
bending,shear,torsionand axialloadsat everysection
shall not be less than the appropriate value at that section produced by the probable mostunfavourable
combination
ofloads on thestructureusing the
appropriate partial safety factors.
35.3LimitStatesofServiceabUlty
35.3.1Deflection
Limiting values of deflectionsare given in23.2.
35.3.2Cracking
Cracking of concrete should notadverselyaffect the
appearanceordurabilityofthestructure;theacceptable
limitsofcrackingwouldvarywiththe typeof structure
andenvironment.Wherespecificattentionis required
to limit
thedesignedcrack widthto aparticularvalue.
crack width calculation
maybe done using formula
given in Annex
F.
Thepractical objective of calculatingcrackwidthis
merely to give guidance to the designer in making
appropriatestructuralarrangementsand in avoiding
grosserrorsindesign,whichmightresultin
concentrationand excessive widthof flexuralcrack.
The surfacewidthof the cracksshouldnot, in general,
exceed 0.3
mm inmembers where cracking is not
harmfuland does not have
anyseriousadverseeffects
uponthepreservationof reinforcing
steelnor uponthe
durabilityofthestructures.Inmemberswherecracking
in the tensile zoneisharmful either becausetheyare
exposed to the effects of the weatheror continuously exposedto moistureor incontactsoil or groundwater,
anupperlimitof0.2mmissuggestedforthe
maximum
widthofcracks.Forparticularlyaggressive
environment,such as the
'severe'category in Table3,
the assessed surface width of cracks should not in
general,exceed0.1 mm.
35.4OtherLimitStates
Structures designed forunusualorspecial functions
shall comply with
anyrelevant additional limit stale
consideredappropriateto that
structure.
36CHARACTERISTIC ANDDESIGN
VALUESANDPARTIALSAFETYFACTORS
36.1CharacteristicStrengthofMaterials
The term 'characteristicstrength' means that valueof
thestrengthofthematerialbelowwhichnotmorethan
5 percent of the test results are expected to fall. The
characteristicstrengthforconcreteshallbe in
accordance
withTable 2. Until the relevant Indian
StandardSpecificationsforreinforcingsteel are
modified to
includethe concept ofcharacteristic
strength, thecharacteristicvalue shall
beassumed as
the minimum yield stress
10.2percent proof stress
specifiedin
therelevantIndianStandardSpecifications.
36.2CharacteristicLoads
The tenn'characteristicload' meansthat valueof load
whichhasa9Spercentprobabilityof notbeingexceeded
during the life of the structure. Since dataarenot
availableto express loads instatisticalterms, for
the
purposeof this standard, dead loads given in IS 875
(Part 1).
imposedloadsgiven in IS 875 (Part
2),wind
loads given in IS 875 (Part 3), snow load as given in
IS 875 (Part 4) and seismic
forcesgiven in IS 1893
shall
beassumedas thecharacteristicloads.
61
IS456:2000
36.3Design
Values
36.3.1Materials
Thedesignstrengthof the
materials.!.Jis givenby
where
f=characteristic strength of the material
(see31).1).and
Ym=partialsafety factorappropriateto the
materialand thelimitstatebeing
considered.
36.3.2Loads
Thedesignload.
FI!is givenby
Fd=FYr
where
F=characteristicload(see36.2).and
Yf=partial safety factorappropriateto the
natureofloadingandthelimitstatebeing
considered.
36.3.3ConsequencesofAttainingLimitState
Wheretheconsequencesofastructureattaininga limit
state are of a serious
naturesuch as huge lossof life
anddisruptionof the
economy.highervaluesfor
Yf
andYmthanthosegivenunder36.4.1and36.4.2may
be
applied.
36.4PartialSafety Factors
36.4.1PartialSafety Factor
YfforLoads
ThevaluesofYfgiveninTable18shallnormallybe
used.
36.4.2PartialSafetyFactorYmfor Mateiral
Strength
36.4.2.1Whenassessingthestrengthof asttucturcor
structuralmemberfor the limit staleofcollapse.
the
valuesofpartialsafety factor.
-r..shouldbetakenas
I.SforconcreteandUSforsteel.
NOTE -y.values are .a1readyincorporatedill the
equations and tablesaivenillthis.tandard forlimitstate.
design.
36.4.2.2Whenassessingthedeflection,thematerial
propertiessuch as
modulusofelasticityshould
be
taken8Sthose associated with the characteristic
strengthof the
material.
37ANALYSIS
37.1Analysisof
Stnacture
Methods of analysis as in 22 shallbeused. The
materialstrengthto beassumedshallbecharacteristic
valuesin thedeterminationof elastic properties.of
membersirrespectiveof the limitstatebeing
considered.Redistributionof thecalculated moments
maybe madeas givenin37.1.1.
37.1.1.RedistributionofMoments in Continuous
Beamsand
Frames
Theredistributionof momentsmay be carried out
satisfyingthe
followingconditions:
a)Equilibirum
betweentheinteralforcesand the
extemalloads ismaintained.
h) The
ultimatemomentofresistanceprovidedat
any section of a member is not less than 70
percentof
themomentat thatsectionobtained
from an elasticmaximummoment diagram
coveringallappropriatecombinationsof loads.
c) Theelastic momentat anysectionina member
due to aparticularcombinationof loads shall
Table 18 ValuesofPartialSafetyFactor
YfforLoads
(Clause.t18.2.3.1.36.4.1andB-4.3)
LoadCombination UnlitState01CoIIapIe LimitStatelof
.. ...
SenlceabUllJ
DL IL WL DL IL WL
(I) (2) (3) (4) (5) (6) (7)
DL+/L I.S 1.0 1.0 1.0
DL+WL I.Sor 1.S 1.0 1.0
091)
... --
..
DL+/L+WL 1.2 1.0 0.8 0.8
NOTES
1 Whileconsideringearthquakeeffects.substituteELforWL
2Forlhe limitstatesofserviceability.thevolucaor1,liveninthistableareapplicableforshantermeffects.Whileasses.inathe
loftgtermeffectsduetoenepthedeadloadandthatpartoftheliveloadlikelytobepermanentmayonlybeconlidered.
nThisvalueis tobeconsideredwhenstabilityapinstoverturningorstressrevenalilcritical.
68
36.3Design
Values
36.3.1Materials
Thedesignstrengthof the
materials.!.Jis givenby
where
f=characteristic strength of the material
(see31).1).and
Ym=partialsafety factorappropriateto the
materialand thelimitstatebeing
considered.
36.3.2Loads
Thedesignload.
FI!is givenby
Fd=FYr
where
F=characteristicload(see36.2).and
Yf=partial safety factorappropriateto the
natureofloadingandthelimitstatebeing
considered.
36.3.3ConsequencesofAttainingLimitState
Wheretheconsequencesofastructureattaininga limit
state are of a serious
naturesuch as huge lossof life
anddisruptionof the
economy.highervaluesfor
Yf
andYmthanthosegivenunder36.4.1and36.4.2may
be
applied.
36.4PartialSafety Factors
36.4.1PartialSafety Factor
YfforLoads
ThevaluesofYfgiveninTable18shallnormallybe
used.
36.4.2PartialSafetyFactorYmfor Mateiral
Strength
36.4.2.1Whenassessingthestrengthof asttucturcor
structuralmemberfor the limit staleofcollapse.
the
valuesofpartialsafety factor.
-r..shouldbetakenas
I.SforconcreteandUSforsteel.
NOTE -y.values are .a1readyincorporatedill the
equations and tablesaivenillthis.tandard forlimitstate.
design.
36.4.2.2Whenassessingthedeflection,thematerial
propertiessuch as
modulusofelasticityshould
be
taken8Sthose associated with the characteristic
strengthof the
material.
37ANALYSIS
37.1Analysisof
Stnacture
Methods of analysis as in 22 shallbeused. The
materialstrengthto beassumedshallbecharacteristic
valuesin thedeterminationof elastic properties.of
membersirrespectiveof the limitstatebeing
considered.Redistributionof thecalculated moments
maybe madeas givenin37.1.1.
37.1.1.RedistributionofMoments in Continuous
Beamsand
Frames
Theredistributionof momentsmay be carried out
satisfyingthe
followingconditions:
a)Equilibirum
betweentheinteralforcesand the
extemalloads ismaintained.
h) The
ultimatemomentofresistanceprovidedat
any section of a member is not less than 70
percentof
themomentat thatsectionobtained
from an elasticmaximummoment diagram
coveringallappropriatecombinationsof loads.
c) Theelastic momentat anysectionina member
due to aparticularcombinationof loads shall
Table 18 ValuesofPartialSafetyFactor
YfforLoads
(Clause.t18.2.3.1.36.4.1andB-4.3)
LoadCombination UnlitState01CoIIapIe LimitStatelof
.. ...
SenlceabUllJ
DL IL WL DL IL WL
(I) (2) (3) (4) (5) (6) (7)
DL+/L I.S 1.0 1.0 1.0
DL+WL I.Sor 1.S 1.0 1.0
091)
... --
..
DL+/L+WL 1.2 1.0 0.8 0.8
NOTES
1 Whileconsideringearthquakeeffects.substituteELforWL
2Forlhe limitstatesofserviceability.thevolucaor1,liveninthistableareapplicableforshantermeffects.Whileasses.inathe
loftgtermeffectsduetoenepthedeadloadandthatpartoftheliveloadlikelytobepermanentmayonlybeconlidered.
nThisvalueis tobeconsideredwhenstabilityapinstoverturningorstressrevenalilcritical.
68
15456:2000
notbereducedby more than 30 percentofthe
numericallylargestmomentgivenanywhereby
the elastic
maximummoments
diagramfor the
particular member. covering
aUappropriate
combinationof loads.
d) At sections
wherethemoment capacity after
redistributionis less than
thatfrom
theelastic
maximum moment diagram. the following
relationshipshall besatisfied:
5L+8MSO.6
d 100
where
Xu=depth ofneutralaxis.
d=effectivedepth.and
6M=percentagereductionin moment.
e) In structures in which the structural frame
provides the lateralstability.thereductionsin
moment allowed by condition
37.1.1(c) shall
berestrictedto
10percentfor
stnacturesover4
storeysin height.
37.1.2 AnalysisofSlabsSpanninginlWoDirections
atRightAngles
Yield line theory or any other acceptable method
may be used. Alternativelytheprovisionsgiven in
AnnexD may be
followed.
38LIMITSTATE OFCOLLAPSE:FLEXURE
38.1Assumpdons
Design for the limit state
ofcollapsein flexure shall
be basedon theassumptionsgiven
below:
a) Planesectionsnonnal to the axis remainplane
afterbending.
b)The
maximumstraininconcreteat the
outennostcompressionfibreis takenas0.0035
in
bending.
c)Therelationshipbetweenthecompressivestress
distributionin
concreteandthesttaininconcrete
maybeassumed toberectangle. trapezoid.
parabola or any other shape which results in
predictionofstrengthinsubstantialagreement
with the results of test.Anacceptablestress
strain curve is given inFig.21. For design
purposes.thecompressivestrengthof concrete
inthestnaetureshallbeassumedtobe0.67times
thecharacteristicstrength. The partial safety
factory.=1.5shallbeappliedinaddition to
this.
NOTE- Pordiestreu·llrlinCUMillrrlJ.21diedeaip
stressblockplIIUIDClerI_ISfollows('flfIPia.22):
Areaofsuessblock • 0.36lot'x.
DepthofcelItleofcolllplaliveforce•0.42x.
from
theextremefimiftcompression
when:
I~
=chancteriaticc:omprasivelballthofconcme.lIIlCI
x.=depChof neutnlWI.
d) The tensilestrengthof theconcreteisignored.
e) Thestressesin thereinforcementare derived
fromrepresentativestress-straincurve for the
type of steel used.'JYpica1curves are given in
Fig. 23. For designpurposesthe partialsafety
factorYm •equalto1.15shallbeapplied.
f)Themaximumstrain in the tensionreinforce
ment in the section at failure shall notbe
less than:
--!:t.-+0.002
1.15E.
_.r-------tfa
where
f,=characteristicstrengthof steel.and
E,=modulusofelasticityof steel.
t
(H7f
Ck
T
III O'42Xu
III
III
Ill:
0.67f
ck
Irm
Xu O·36f
c kXu
t-
III
~
0·002 0·03S
STRAIN-
FIG.21STRESS-STRAINCURVER>RCONCREm FIG.22STRESSBLOCKPARAME'I1!RS
69
notbereducedby more than 30 percentofthe
numericallylargestmomentgivenanywhereby
the elastic
maximummoments
diagramfor the
particular member. covering
aUappropriate
combinationof loads.
d) At sections
wherethemoment capacity after
redistributionis less than
thatfrom
theelastic
maximum moment diagram. the following
relationshipshall besatisfied:
5L+8MSO.6
d 100
where
Xu=depth ofneutralaxis.
d=effectivedepth.and
6M=percentagereductionin moment.
e) In structures in which the structural frame
provides the lateralstability.thereductionsin
moment allowed by condition
37.1.1(c) shall
berestrictedto
10percentfor
stnacturesover4
storeysin height.
37.1.2 AnalysisofSlabsSpanninginlWoDirections
atRightAngles
Yield line theory or any other acceptable method
may be used. Alternativelytheprovisionsgiven in
AnnexD may be
followed.
38LIMITSTATE OFCOLLAPSE:FLEXURE
38.1Assumpdons
Design for the limit state
ofcollapsein flexure shall
be basedon theassumptionsgiven
below:
a) Planesectionsnonnal to the axis remainplane
afterbending.
b)The
maximumstraininconcreteat the
outennostcompressionfibreis takenas0.0035
in
bending.
c)Therelationshipbetweenthecompressivestress
distributionin
concreteandthesttaininconcrete
maybeassumed toberectangle. trapezoid.
parabola or any other shape which results in
predictionofstrengthinsubstantialagreement
with the results of test.Anacceptablestress
strain curve is given inFig.21. For design
purposes.thecompressivestrengthof concrete
inthestnaetureshallbeassumedtobe0.67times
thecharacteristicstrength. The partial safety
factory.=1.5shallbeappliedinaddition to
this.
NOTE- Pordiestreu·llrlinCUMillrrlJ.21diedeaip
stressblockplIIUIDClerI_ISfollows('flfIPia.22):
Areaofsuessblock • 0.36lot'x.
DepthofcelItleofcolllplaliveforce•0.42x.
from
theextremefimiftcompression
when:
I~
=chancteriaticc:omprasivelballthofconcme.lIIlCI
x.=depChof neutnlWI.
d) The tensilestrengthof theconcreteisignored.
e) Thestressesin thereinforcementare derived
fromrepresentativestress-straincurve for the
type of steel used.'JYpica1curves are given in
Fig. 23. For designpurposesthe partialsafety
factorYm •equalto1.15shallbeapplied.
f)Themaximumstrain in the tensionreinforce
ment in the section at failure shall notbe
less than:
--!:t.-+0.002
1.15E.
_.r-------tfa
where
f,=characteristicstrengthof steel.and
E,=modulusofelasticityof steel.
t
(H7f
Ck
T
III O'42Xu
III
III
Ill:
0.67f
ck
Irm
Xu O·36f
c kXu
t-
III
~
0·002 0·03S
STRAIN-
FIG.21STRESS-STRAINCURVER>RCONCREm FIG.22STRESSBLOCKPARAME'I1!RS
69
18456:2000
SlRAIN--.
••-ZOOOOO"/".".2
~..------fy
/,
,
I
I
I
I
I
I
I
I
I
,
I,
I,
·0001
'000'
-0001
t
STRESS
23AColdWorkedDefonnedBar
'r
t
,..--------"
l--------"".15
£,-200000N/mm'
238STEELBARWITH0mNn'EYIELDPOINT
FlO.23REPRESENrATIVBSTRESS-S11tA1NCURVESfORRElNPORCBMENT
NOTE-Thelimitingvaluesof thedepthofneutraluisfor
diffe~nlgradesof steelbasedontheassumptionsin31.1118as
foUows:
Theexpression for obtaining the moments0'rea.iltancefor
~e:tanlUlar andT-Sectionl.bIIlldOIlthelIIUIIIpliouof.1,118
giveninAnnexG.
39LIMITSTATEOFCOLLAPSE:
COMPRESSION
39.1
AlSUlDpdoMInadditionto'theassumptionsgivenin38.1<a)to
f.,
2SO
415
SOO
x.._ld
O.~3
0.48
0.46
38.1(c) forflexure,thefollowingshallbeassumed:
a)1bemaximumcompressivestraininconcrete
inaxialcompressionistakenas0.002.
b)1bemaximumcompressivestrainatthehighly
compressedextremefibreinconcretesubjected
toaxialcompressionandbendingandwhen
thereisnotensiononthesectionshallbe0.003S
minus0.75times thestrainat the least
compressedextremefibre.
39.2MW-wEeceatrIdty
Allmembersincompressionshallbedesignedforthe
minimumeccentricityinICCOIdancewith25.4.Where
70
SlRAIN--.
••-ZOOOOO"/".".2
~..------fy
/,
,
I
I
I
I
I
I
I
I
I
,
I,
I,
·0001
'000'
-0001
t
STRESS
23AColdWorkedDefonnedBar
'r
t
,..--------"
l--------"".15
£,-200000N/mm'
238STEELBARWITH0mNn'EYIELDPOINT
FlO.23REPRESENrATIVBSTRESS-S11tA1NCURVESfORRElNPORCBMENT
NOTE-Thelimitingvaluesof thedepthofneutraluisfor
diffe~nlgradesof steelbasedontheassumptionsin31.1118as
foUows:
Theexpression for obtaining the moments0'rea.iltancefor
~e:tanlUlar andT-Sectionl.bIIlldOIlthelIIUIIIpliouof.1,118
giveninAnnexG.
39LIMITSTATEOFCOLLAPSE:
COMPRESSION
39.1
AlSUlDpdoMInadditionto'theassumptionsgivenin38.1<a)to
f.,
2SO
415
SOO
x.._ld
O.~3
0.48
0.46
38.1(c) forflexure,thefollowingshallbeassumed:
a)1bemaximumcompressivestraininconcrete
inaxialcompressionistakenas0.002.
b)1bemaximumcompressivestrainatthehighly
compressedextremefibreinconcretesubjected
toaxialcompressionandbendingandwhen
thereisnotensiononthesectionshallbe0.003S
minus0.75times thestrainat the least
compressedextremefibre.
39.2MW-wEeceatrIdty
Allmembersincompressionshallbedesignedforthe
minimumeccentricityinICCOIdancewith25.4.Where
70
calculatedeccentricityis larger, the minimum
eccentricityshould
be
ignored.
39.3ShortAxiallyLoadecIMe.benin
COlDpnaloD
Themember shallbedesignedbyconsideringthe
assumptionsgiven in39.1andtheminimum
eccentricity. When the minimum eccentricity as
per25.4does not exceedO.OStimesthe lateral
dimension,the membersmaybe designed bythe
followinsequation:
. PI=0.4'et.A
c+0.67f,.A
Ie
where
P
u
•axialload on themember.
I..=characteristiccompressivestrensthofthe
concrete,
A
c=Areaofconcrete,
t,=characteristicstrengthofthecompression
reinforcement,and
Ale==areaoflongitudinalreinforcementfor
columns.
39.4CompressionMembenwithReDeal
Relnforcemeat
The strength ofcompression memberswithhelical
reinforcementsatisfyin.therequirementof39.4.1shall
betakenas1.0~timesthestrensthof similarmember
withlateralties.
39.4.1Theratioofthevolumeofhelicalreinforcement
to the volume of the core shall not be lessthan
0.36(A.IAc-l)f*'f,
where
A.=pssareaof thesection,
A
c=areaofthecoreofthehelicallyreinforced
columnmeasuredtotheoutsidediameter
of thehelix,
fa•characteristiccompressivestrensthofthe
concrete,and
I,=characteristicstrength of the helical
reinforcementbut notexceeding
41~N/mm2.
39.5MembenSubjectedtoCombinedAxial
Load aDdUnlulalBeDeIlD,
Amembersubjectedtoaxialforceanduniaxialbending
shallbedesisnedon the basisof 39.1and39.3.
NOTE-Thedeli...ofmemberlubjecttocombineduialload
anduniuialbendin. willinvolveleftIlhycalculationbytrill
anderror.In orcI. toovercomethesedifticuldesintonacuoD
diql1UDlmaybeUIed.The.havebeenprepandaDdpublished
by 8 ISin•SP : 16Deilinaidaforreinforcedconcretoto
IS456'.
71
IS
456:2000
39.6MembersSubjectedtoCombinedAxialLoad
andBiaxialBenellD.
Theresistanceof a membersubjectedto axial force
andbiaxial
bendingshallbeobtainedon the basis of
assumptionsgivenin39.1and
39.2with neutralaxis
sochosenas to satisfy theequilibriumof load and
momentsabouttwoaxes.Alternativelysuch members
maybedesignedbythefollowingequation:
[
~ ]a.+ [Muy]a.S10
Alux1 Atu~1 •
where
=momentsaboutxandyaxes
due todesignloads,
M
U l tM
aYI=maximum uniaxial moment
capacityforanaxialloadofP
u
'
bending aboutxand
yaxes
respectively,and
Q.is relatedtoPulP
tJI
whereP
y Z=0.4Slet·A
c
+0.7S1,.Ale
ForvaluesofPu'PUI=0.2 to0.8, the valuesofa.vary
linearly
from1.0to 2.0.Forvalueslessthan0.2,aais
1.0;forvalues
greaterthan0.8.Q.is2.0.
39.7Slender
Comp
....lonMemben
The design ,ofslendercompressionmembers
(see25.1.1)shallbe based on theforces and the
momentsdeterminedfromananalysisofthestructure,
including
theeffect ofdeflectionson momentsand
forces.Whenthe
effectofdeflectionsare not taken
Intoaccountintheanalysis.additionalmomentgiven
in39.7.1shallbetakenintoaccountintheappropriate
direction.
39.7.1TheadditionalmomentsM.andM.'Ishall
be
calculatedbythe~ollowinl fonnulae:
M=PyD{!a.}2
u2000D
M•..M..{!.2.}2
.y2000b
where
P
u=axialloadon themember,
la=effectivelength in respect of the major
axis.
'ey=effectivelenlthinrespectoftheminoraxis.
D=depth of thecross-sectionat right angles
to themajoraxis,and
b=widthof themember.
Fordesignofsection,39.5or39.6asappropriateshall
apply.
eccentricityshould
be
ignored.
39.3ShortAxiallyLoadecIMe.benin
COlDpnaloD
Themember shallbedesignedbyconsideringthe
assumptionsgiven in39.1andtheminimum
eccentricity. When the minimum eccentricity as
per25.4does not exceedO.OStimesthe lateral
dimension,the membersmaybe designed bythe
followinsequation:
. PI=0.4'et.A
c+0.67f,.A
Ie
where
P
u
•axialload on themember.
I..=characteristiccompressivestrensthofthe
concrete,
A
c=Areaofconcrete,
t,=characteristicstrengthofthecompression
reinforcement,and
Ale==areaoflongitudinalreinforcementfor
columns.
39.4CompressionMembenwithReDeal
Relnforcemeat
The strength ofcompression memberswithhelical
reinforcementsatisfyin.therequirementof39.4.1shall
betakenas1.0~timesthestrensthof similarmember
withlateralties.
39.4.1Theratioofthevolumeofhelicalreinforcement
to the volume of the core shall not be lessthan
0.36(A.IAc-l)f*'f,
where
A.=pssareaof thesection,
A
c=areaofthecoreofthehelicallyreinforced
columnmeasuredtotheoutsidediameter
of thehelix,
fa•characteristiccompressivestrensthofthe
concrete,and
I,=characteristicstrength of the helical
reinforcementbut notexceeding
41~N/mm2.
39.5MembenSubjectedtoCombinedAxial
Load aDdUnlulalBeDeIlD,
Amembersubjectedtoaxialforceanduniaxialbending
shallbedesisnedon the basisof 39.1and39.3.
NOTE-Thedeli...ofmemberlubjecttocombineduialload
anduniuialbendin. willinvolveleftIlhycalculationbytrill
anderror.In orcI. toovercomethesedifticuldesintonacuoD
diql1UDlmaybeUIed.The.havebeenprepandaDdpublished
by 8 ISin•SP : 16Deilinaidaforreinforcedconcretoto
IS456'.
71
IS
456:2000
39.6MembersSubjectedtoCombinedAxialLoad
andBiaxialBenellD.
Theresistanceof a membersubjectedto axial force
andbiaxial
bendingshallbeobtainedon the basis of
assumptionsgivenin39.1and
39.2with neutralaxis
sochosenas to satisfy theequilibriumof load and
momentsabouttwoaxes.Alternativelysuch members
maybedesignedbythefollowingequation:
[
~ ]a.+ [Muy]a.S10
Alux1 Atu~1 •
where
=momentsaboutxandyaxes
due todesignloads,
M
U l tM
aYI=maximum uniaxial moment
capacityforanaxialloadofP
u
'
bending aboutxand
yaxes
respectively,and
Q.is relatedtoPulP
tJI
whereP
y Z=0.4Slet·A
c
+0.7S1,.Ale
ForvaluesofPu'PUI=0.2 to0.8, the valuesofa.vary
linearly
from1.0to 2.0.Forvalueslessthan0.2,aais
1.0;forvalues
greaterthan0.8.Q.is2.0.
39.7Slender
Comp
....lonMemben
The design ,ofslendercompressionmembers
(see25.1.1)shallbe based on theforces and the
momentsdeterminedfromananalysisofthestructure,
including
theeffect ofdeflectionson momentsand
forces.Whenthe
effectofdeflectionsare not taken
Intoaccountintheanalysis.additionalmomentgiven
in39.7.1shallbetakenintoaccountintheappropriate
direction.
39.7.1TheadditionalmomentsM.andM.'Ishall
be
calculatedbythe~ollowinl fonnulae:
M=PyD{!a.}2
u2000D
M•..M..{!.2.}2
.y2000b
where
P
u=axialloadon themember,
la=effectivelength in respect of the major
axis.
'ey=effectivelenlthinrespectoftheminoraxis.
D=depth of thecross-sectionat right angles
to themajoraxis,and
b=widthof themember.
Fordesignofsection,39.5or39.6asappropriateshall
apply.
18456:__
NOTES
1 AcolumnmaybeconsideredbrKedinaJivenplaneif1alaal
stabilitytotheI1nICtUIe• IwholeisprovidedbywaUlor
bracin.orbultJaliDidelipedto..illaIl1alerllf-.in
thatplane.Itshouldotberwi.beeoDlictered_UDbncecI.
2Inthecueof abmcedcola..withoutuytnnmneloadl
occurriqinitaheiPt,the additionalmomentIhallbeadded
toaninidalmomeDtequalto lum of0.4MI'and0.6"'w2
whereMwjisthelaqerendmomentandMI'isthesmaller
endmoment(IllUmedneptiveIfthecolumniIbentindouble
curvature).InDOCIIeshalltheinitialmolDeD!belei.than
0.4M.
2
norIhctotalmomeatincluclillltheinitialmomeatbe
lesathaDM
d
-For\1Dbracedcolumu,theIdditiODllmoment
shallbeaddedtotheendmomenta.
3UnbrKedcompmsionmemben.11anylivenlevelor1tOre)'.
lubjecttolateralloadareUluallycoDltrainedtocleftect
equally.InsuChcueallenclcmeuredoforuclacolUllUlmay
betaken_the_venaeforalleolUIDDIICtinIillthesame
diJection.
39.7.1.1Thevaluesgivenbyequation39.7.1maybe
multipliedbythefollowinsfactor:
,,=P",-IjSI
PUI-I\
where
p.• axialloadoncompressionmember,
p.=asdefinedin39.6,and
Ph=axialloadcorrespondingtothecondition
of maximum compressive strain of
0.0035inconcreteandtensilestrainof
0.002inoutermostlayeroftensionsteel.
40 LIMITSTATEOF COLLAPSE:SHEAR
40.1NomIuIShearS.....
Thenominalshear,tressinbeamsofunifonndepth
Aballbeobtainedbythefollowinaequation:
~.
t
y
•.:.L
b.
where
V.:Ishearforceduetodesiploads;
b• breadthofthemember,whichforflanled
sectionshallbetakenuthebreadthof
theweb.b..:and
d=effectivedepth.
40.1.1B'DmIofVaryingDepth
InthecaseofbeamsofvaryinSdepththeequation
shallbemodifiedu:
V.:I:M,tanfJ
f••d
v btl
where
1v'V.'banddarethesameasin40.1.
M••bendinlmomentatthesection,and
~•anilebetweenthetopandthebottomedps
of thebeam.
Thenegativesignin the fonnul.applieswhenthe
bendingmomentMyincreasesnumericallyinthesame
directionas theeffectivedepthdincreases.and the
positivesignwhenthemomentdecreasesnumerically
in thisdirection.
40.2DesipShearStrenath01Coaerete
40.2.1Thedesignshearstrengthofconcretein beams
withoutshearreinforcementisliveninTable19.
40.11.1Forsolidslabs,thedesi,n shearstrengthfor
concreteshallbefele,whereIehasthevaluesgiven
below:
OverallDtpth300or275150m200175ISOor
01Slab,mmmore less
Ie 1.001.0S1.10I.IS1.201.251.30
NOYS-nulprovilionshallnotapplytoflatslabaforwhicb
31.6shallapply.
40.2.2ShearStrengthofMtmbtrsundtr Axial
Compression
FormemberssubjectedtoaxialcompressionP
u
'
the
designshearstrengthofconcrete,
giveninTable19,
shallbemultipliedbythefollowingfactor:
6I2.!L=+A'but·notexceeding1.5
IJet
where
P
u=axialcompressiveforceinNewtons,
A.=grossareaoftheconcrete sectioninmm',
and
let.=characteristiccompressivestl1nathof
concrete.
40.13WithShe"rReinforcement
Undernocircumstances.even with shear
reinforcement.shallthenominalshearstressinbeams
tvexecedt
cmu
liven inTable20.
40.2.3.1For solid slabs, thenominalshear stress
shallnotexceedhalftheappropriatevaluesgivenin
Table20.
40.3MInimumShearRelDforeement
Whentvis lessthan'tcliveninTable19,minimum
shearreinforcementshallbeprovidedinaccordance
with26.5.1.6.
40.4DesApofShearlleIIlforeemeDt
Whene,exceeds1
cgiven in Table 19. shear
reinforcementshallbeprovidedinanyofthefollowing
forms:
a)Verticalstinups.
b)Bent-upbanalonawithstirrups,and
72
NOTES
1 AcolumnmaybeconsideredbrKedinaJivenplaneif1alaal
stabilitytotheI1nICtUIe• IwholeisprovidedbywaUlor
bracin.orbultJaliDidelipedto..illaIl1alerllf-.in
thatplane.Itshouldotberwi.beeoDlictered_UDbncecI.
2Inthecueof abmcedcola..withoutuytnnmneloadl
occurriqinitaheiPt,the additionalmomentIhallbeadded
toaninidalmomeDtequalto lum of0.4MI'and0.6"'w2
whereMwjisthelaqerendmomentandMI'isthesmaller
endmoment(IllUmedneptiveIfthecolumniIbentindouble
curvature).InDOCIIeshalltheinitialmolDeD!belei.than
0.4M.
2
norIhctotalmomeatincluclillltheinitialmomeatbe
lesathaDM
d
-For\1Dbracedcolumu,theIdditiODllmoment
shallbeaddedtotheendmomenta.
3UnbrKedcompmsionmemben.11anylivenlevelor1tOre)'.
lubjecttolateralloadareUluallycoDltrainedtocleftect
equally.InsuChcueallenclcmeuredoforuclacolUllUlmay
betaken_the_venaeforalleolUIDDIICtinIillthesame
diJection.
39.7.1.1Thevaluesgivenbyequation39.7.1maybe
multipliedbythefollowinsfactor:
,,=P",-IjSI
PUI-I\
where
p.• axialloadoncompressionmember,
p.=asdefinedin39.6,and
Ph=axialloadcorrespondingtothecondition
of maximum compressive strain of
0.0035inconcreteandtensilestrainof
0.002inoutermostlayeroftensionsteel.
40 LIMITSTATEOF COLLAPSE:SHEAR
40.1NomIuIShearS.....
Thenominalshear,tressinbeamsofunifonndepth
Aballbeobtainedbythefollowinaequation:
~.
t
y
•.:.L
b.
where
V.:Ishearforceduetodesiploads;
b• breadthofthemember,whichforflanled
sectionshallbetakenuthebreadthof
theweb.b..:and
d=effectivedepth.
40.1.1B'DmIofVaryingDepth
InthecaseofbeamsofvaryinSdepththeequation
shallbemodifiedu:
V.:I:M,tanfJ
f••d
v btl
where
1v'V.'banddarethesameasin40.1.
M••bendinlmomentatthesection,and
~•anilebetweenthetopandthebottomedps
of thebeam.
Thenegativesignin the fonnul.applieswhenthe
bendingmomentMyincreasesnumericallyinthesame
directionas theeffectivedepthdincreases.and the
positivesignwhenthemomentdecreasesnumerically
in thisdirection.
40.2DesipShearStrenath01Coaerete
40.2.1Thedesignshearstrengthofconcretein beams
withoutshearreinforcementisliveninTable19.
40.11.1Forsolidslabs,thedesi,n shearstrengthfor
concreteshallbefele,whereIehasthevaluesgiven
below:
OverallDtpth300or275150m200175ISOor
01Slab,mmmore less
Ie 1.001.0S1.10I.IS1.201.251.30
NOYS-nulprovilionshallnotapplytoflatslabaforwhicb
31.6shallapply.
40.2.2ShearStrengthofMtmbtrsundtr Axial
Compression
FormemberssubjectedtoaxialcompressionP
u
'
the
designshearstrengthofconcrete,
giveninTable19,
shallbemultipliedbythefollowingfactor:
6I2.!L=+A'but·notexceeding1.5
IJet
where
P
u=axialcompressiveforceinNewtons,
A.=grossareaoftheconcrete sectioninmm',
and
let.=characteristiccompressivestl1nathof
concrete.
40.13WithShe"rReinforcement
Undernocircumstances.even with shear
reinforcement.shallthenominalshearstressinbeams
tvexecedt
cmu
liven inTable20.
40.2.3.1For solid slabs, thenominalshear stress
shallnotexceedhalftheappropriatevaluesgivenin
Table20.
40.3MInimumShearRelDforeement
Whentvis lessthan'tcliveninTable19,minimum
shearreinforcementshallbeprovidedinaccordance
with26.5.1.6.
40.4DesApofShearlleIIlforeemeDt
Whene,exceeds1
cgiven in Table 19. shear
reinforcementshallbeprovidedinanyofthefollowing
forms:
a)Verticalstinups.
b)Bent-upbanalonawithstirrups,and
72
18456:2000
Table19DesIpShear~tre"'" 01Concrete,'t
c
'NI.....r
(Cltuues4O.2.1.40.2.2.40.3.40.4.4O.S.3.41.3.2.41.3.3and41.4.3)
l00~ CoDcnteGnde
btl ,..
,
-MIS M20 M2S M30 M3S M40IIldabove
(l) (2) (3) (4) (5) (6) (7)
~0.t5 0.28 0.28 0.29 0.29 0.29 0.30
0.25 0.35 0.36 0.36 0.37 0.37 0.38
0.50 0.46 0.48 0.49 0.50 0.50 0.51
0.1S 0.54 0.56 0.$1 0.59 0.59 0.60
1.00 0.60 0.62 0.64 0.66 0.61 0.68
1.2S 0.64 0.61 0.10 0.11 0.73 0.74
I.SO 0.68 0.12 0.14 0.76 0.18 0.79
1.1S 0.11 0.7S 0.78 0.80 0.82 0.84
2.00
0.11 0.79 0.82 0.84 0.86 0.882.25 0.11 0.81 0.85 0.88 0.90 0.92
2.50 0.11 0.82 0.88 0.9t 0.93 0.95
2.7S 0.71 0.82 0.90 0.94 0.96 0.98
3.00 0.71 0.82 0.92 0.96 0.99 1.01
nnd
above
NOTE-ThetermAIsthearelloflonaltudinll1ten.lonreinforcementwhichconllnuesatIClIStoneeffectivedepthbeyondthesection
bein,consideredexc;ptatsupponwherethefullareaoftensionreinforcementmaybeusedprovidedthedetllilinaconfonn.to16.1.1
and26.1.3
Table10MaximumShearStress,f
c_ll,N/mm
J
(Cia",,,40.2.3.40.2.3.1.4O.S.1arad41.3.1)
Concrete
Gncle
MIS
2.5
M20
2.'
M2S
3.1
M30
3.S
M3S
3.7
M40
lIIId
IIbove
4.0
c)Inclinedstirrups.
Wherebent-upbarsareprovided.theircontribution
towardsshearresistancethannotbemorethanhalf
thatof thetotalshearreinforcement.
Shearreinforcementshallbeprovidedtocarryashear
equaltoV
u
-f'~bdTheatrenathofahcarreinforce
mentV...shallbecalculatedubelow:
a)Forverticalstirrupa:
_
0._87
...;./',...1A,...;.y~d
V
U1
•
Iv
b) Forinclinedstirrupsor aseriesofbarlbent-up
atdifferentcross-sections:
0.8.7Iy.-\vd( . )
V
U1
• sma+cosa
s
v
c) For5in,1ebar or5in,Iegroupofparallelbars.
allbent-upat thesamecross-section:
21H1815/07_11
73
where
A II:totalcross-sectionalareaofstirruplegs
••
orbent-upbanwithinadistances.'
s.•specinaofthestirrupsorbent-upbars
alonathelenathof themember,
'tvIIInc)tninalshearSIre.S,
e,II:desianshearstrenathof theconcrete.
b IIIbreadth of the member which for
flan.edbeams,shallbetakenasthe
breadthof thewebb••
I
r=characteristicItrenJthofthestirrupor
bent-upreinforcementwhichshallnot
be
taken
Jreaterthan41~N/mm
2
,
a IIIanalebetweentheinclinedstirrupor
bent-upbarandtheaxisofthemember.
notlessthan4'°.and
d:;effectivedepth.
Table19DesIpShear~tre"'" 01Concrete,'t
c
'NI.....r
(Cltuues4O.2.1.40.2.2.40.3.40.4.4O.S.3.41.3.2.41.3.3and41.4.3)
l00~ CoDcnteGnde
btl ,..
,
-MIS M20 M2S M30 M3S M40IIldabove
(l) (2) (3) (4) (5) (6) (7)
~0.t5 0.28 0.28 0.29 0.29 0.29 0.30
0.25 0.35 0.36 0.36 0.37 0.37 0.38
0.50 0.46 0.48 0.49 0.50 0.50 0.51
0.1S 0.54 0.56 0.$1 0.59 0.59 0.60
1.00 0.60 0.62 0.64 0.66 0.61 0.68
1.2S 0.64 0.61 0.10 0.11 0.73 0.74
I.SO 0.68 0.12 0.14 0.76 0.18 0.79
1.1S 0.11 0.7S 0.78 0.80 0.82 0.84
2.00
0.11 0.79 0.82 0.84 0.86 0.882.25 0.11 0.81 0.85 0.88 0.90 0.92
2.50 0.11 0.82 0.88 0.9t 0.93 0.95
2.7S 0.71 0.82 0.90 0.94 0.96 0.98
3.00 0.71 0.82 0.92 0.96 0.99 1.01
nnd
above
NOTE-ThetermAIsthearelloflonaltudinll1ten.lonreinforcementwhichconllnuesatIClIStoneeffectivedepthbeyondthesection
bein,consideredexc;ptatsupponwherethefullareaoftensionreinforcementmaybeusedprovidedthedetllilinaconfonn.to16.1.1
and26.1.3
Table10MaximumShearStress,f
c_ll,N/mm
J
(Cia",,,40.2.3.40.2.3.1.4O.S.1arad41.3.1)
Concrete
Gncle
MIS
2.5
M20
2.'
M2S
3.1
M30
3.S
M3S
3.7
M40
lIIId
IIbove
4.0
c)Inclinedstirrups.
Wherebent-upbarsareprovided.theircontribution
towardsshearresistancethannotbemorethanhalf
thatof thetotalshearreinforcement.
Shearreinforcementshallbeprovidedtocarryashear
equaltoV
u
-f'~bdTheatrenathofahcarreinforce
mentV...shallbecalculatedubelow:
a)Forverticalstirrupa:
_
0._87
...;./',...1A,...;.y~d
V
U1
•
Iv
b) Forinclinedstirrupsor aseriesofbarlbent-up
atdifferentcross-sections:
0.8.7Iy.-\vd( . )
V
U1
• sma+cosa
s
v
c) For5in,1ebar or5in,Iegroupofparallelbars.
allbent-upat thesamecross-section:
21H1815/07_11
73
where
A II:totalcross-sectionalareaofstirruplegs
••
orbent-upbanwithinadistances.'
s.•specinaofthestirrupsorbent-upbars
alonathelenathof themember,
'tvIIInc)tninalshearSIre.S,
e,II:desianshearstrenathof theconcrete.
b IIIbreadth of the member which for
flan.edbeams,shallbetakenasthe
breadthof thewebb••
I
r=characteristicItrenJthofthestirrupor
bent-upreinforcementwhichshallnot
be
taken
Jreaterthan41~N/mm
2
,
a IIIanalebetweentheinclinedstirrupor
bent-upbarandtheaxisofthemember.
notlessthan4'°.and
d:;effectivedepth.
IS456:2000
NOTES
1 Where more(hanonetypeofshearreinforcementis used
to reinforcethe same portion
ofthe
beam.the totalshear
resistanceshallbecomputedasthesumoftheresistance
for the varioustypesseparately.
2Theareaofthestirrupsshallnotbelessthantheminimum
specifiedin26.5.1.6.
40.5EnhancedShearStrengthofSectionsClose
to
Supports
40.5.1General
Shear failure at sections of beams and cantilevers
without shearreinforcement wiIJnormallyoccur on
plane inclined at
anangle 30° to the horizontal. If the
angleoffailure planeisforcedto be inclined more
steeply
than this [because thesectionconsidered
(X -
X)in Fig. 24 is close to
asupport or for other
reasons},the shear
forcerequiredtoproduce failure
is
increased.
The enhancement of shear strengthmayhetaken
into
accountin the design of
sectionsnearasupport
by
increasing design shear strength of concrete to
2d
reIa;providedthat designshearstressattheface
of the support remains less than thevaluesgiven in
Table 20. Accountmaybe taken of the enhancement
in
anysituation where the sectionconsideredis closer
to thefaceof a supportorconcentrated
loadthantwice
theeffectivedepth.d.To beeffective.tension
reinforcementshouldextendon each side ofthepoint
whereitis intersectedbya possible failure plane fora
distance atleastequal to the effective depth, or be
provided with an equiv rlent anchorage.
40.5.2Shear ReinforcementforSections Close to .
Supports
If shearreinforcementisrequired.thetotalareaof this
is given
by:
AI'=ayb(Tv-2dfJa,)I0.87/"~O.4a
yb/O.87~
Thisreinforcementshouldbeprovidedwithinthemiddle
threequartersof(lv'wherea
yis lessthand.horizontal
shear
reinforcementwillbeeffectivethanvertical.
40.5.3 EnhancedShear Strength Near Supports
(Simplified
Approach)
Theproceduregivenin40.5.1and40.5.2maybeused
for all beams. However for beamscarryinggenerally
uniform load or where theprincipalload islocated
farther than 2d from the face of support, the shear
stress
maybe calculated at a section a distancedfrom
the face of support. The value of
t
c
is calculated in
accordance with Table 19 andappropriateshear
reinforcement
is providedatsections closer tothe
support, nofunhercheck for shear at such sections is
required.
41LIMITSTA1'EOFCOLLAPSE:TORSION
41.1General
Instructures,where torsion is required to maintain
equilibrium,
membersshallbedesignedfortorsionin
accordancewith41.2,41.3and41.4.However.forsuch
indeterminatestructureswheretorsioncanbeeliminated
byreleasingredundantrestraints.nospecific designfor
torsion is necessary, provided torsional stiffness is
neglectedin the
calculationofinternalforces.Adequate
controlofanytorsionalcrackingisprovidedbytheshear
reinforcementas per
40.
N()TE - The approach to
designin this clause isasfollows:
Torsionalreinforcementis notcalculatedseparatelyfromthat
requiredforbendingandshear.Insteadthelotallongitudinal
reinforcementis determined for a fictitious bendingmoment
whichisafunctionof actual bending moment and torsion;
NOTE- Theshearcausingfailureisthatoctingon,sectionX-X.
FIG.24SHEARFAILURENEARSUPPORTS
74
NOTES
1 Where more(hanonetypeofshearreinforcementis used
to reinforcethe same portion
ofthe
beam.the totalshear
resistanceshallbecomputedasthesumoftheresistance
for the varioustypesseparately.
2Theareaofthestirrupsshallnotbelessthantheminimum
specifiedin26.5.1.6.
40.5EnhancedShearStrengthofSectionsClose
to
Supports
40.5.1General
Shear failure at sections of beams and cantilevers
without shearreinforcement wiIJnormallyoccur on
plane inclined at
anangle 30° to the horizontal. If the
angleoffailure planeisforcedto be inclined more
steeply
than this [because thesectionconsidered
(X -
X)in Fig. 24 is close to
asupport or for other
reasons},the shear
forcerequiredtoproduce failure
is
increased.
The enhancement of shear strengthmayhetaken
into
accountin the design of
sectionsnearasupport
by
increasing design shear strength of concrete to
2d
reIa;providedthat designshearstressattheface
of the support remains less than thevaluesgiven in
Table 20. Accountmaybe taken of the enhancement
in
anysituation where the sectionconsideredis closer
to thefaceof a supportorconcentrated
loadthantwice
theeffectivedepth.d.To beeffective.tension
reinforcementshouldextendon each side ofthepoint
whereitis intersectedbya possible failure plane fora
distance atleastequal to the effective depth, or be
provided with an equiv rlent anchorage.
40.5.2Shear ReinforcementforSections Close to .
Supports
If shearreinforcementisrequired.thetotalareaof this
is given
by:
AI'=ayb(Tv-2dfJa,)I0.87/"~O.4a
yb/O.87~
Thisreinforcementshouldbeprovidedwithinthemiddle
threequartersof(lv'wherea
yis lessthand.horizontal
shear
reinforcementwillbeeffectivethanvertical.
40.5.3 EnhancedShear Strength Near Supports
(Simplified
Approach)
Theproceduregivenin40.5.1and40.5.2maybeused
for all beams. However for beamscarryinggenerally
uniform load or where theprincipalload islocated
farther than 2d from the face of support, the shear
stress
maybe calculated at a section a distancedfrom
the face of support. The value of
t
c
is calculated in
accordance with Table 19 andappropriateshear
reinforcement
is providedatsections closer tothe
support, nofunhercheck for shear at such sections is
required.
41LIMITSTA1'EOFCOLLAPSE:TORSION
41.1General
Instructures,where torsion is required to maintain
equilibrium,
membersshallbedesignedfortorsionin
accordancewith41.2,41.3and41.4.However.forsuch
indeterminatestructureswheretorsioncanbeeliminated
byreleasingredundantrestraints.nospecific designfor
torsion is necessary, provided torsional stiffness is
neglectedin the
calculationofinternalforces.Adequate
controlofanytorsionalcrackingisprovidedbytheshear
reinforcementas per
40.
N()TE - The approach to
designin this clause isasfollows:
Torsionalreinforcementis notcalculatedseparatelyfromthat
requiredforbendingandshear.Insteadthelotallongitudinal
reinforcementis determined for a fictitious bendingmoment
whichisafunctionof actual bending moment and torsion;
NOTE- Theshearcausingfailureisthatoctingon,sectionX-X.
FIG.24SHEARFAILURENEARSUPPORTS
74
similarlywebreinforcementisdeterminedfor3fictitiousshear
whichisafunctionofactualshearandtorsion.
41.1.1Thedesignruleslaiddownin 41.3 and 41.4
shallapplyto beams of solid rectangularcross..section.
However, theseclausesmayalso be appliedtoflanged
beams,bysubstituting b
w
forbin which casetheyare
generally conservative;thereforespecialist literature
maybereferred to.
41.2CriticalSection
Sectionslocatedless than adistance d.from theface
ofthesupportmaybedesignedforthesametorsionas
computed at a distanced,wheredis theeffectivedepth.
41.3ShearandTorsion
41.3.1EquivalentShear
Equivalentshear,V
c
'
shall becalculatedfrom the
formula:
where
V
=equivalent.shear,
,"
V=
shear,
u
1·=torsionalmoment,and
u
b= breadthofbeam,
The equivalentnominalshearstress.'tv...in thiscase
shallbecalculatedasgivenin40.1,exceptfor
substituting\'uhyV
c
'The values ofrvcshallnotexceed
thevaluesoftt'mallgiveninTable20.
41.3.2 If the equivalentnominalshearstress,'t\'l'docs
notexceedtl'givenin.ablc19,minimumshear
reinforcementshallhe providedasper26.5.1.6.
41.3.3Iftv\.exceedst,giveninTable19.both
longitudinal andtransversereinforcementshallhe
provided inaccordancewith41.4.
41.4Reinforcementin MembersSubjectedto
Torsion
41.4.1 Reinforcementfortorsion,when
required,shall
consistof longitudinalandtransversereinforcement,
41.4.2LongitudinalReinforcement
The
longitudinalreinforcementshall
hedesignedto
resistan equivalent bending1l10111Cnl,M
d
-givenby
M
d
=M
u
+M,
where
M
u=bending moment at thecross-section,and
M.=t:(.I+!Jlb·)
u 1.7
IS456:2000
where
'~Iisthetorsionalmoment,Dis the overalldepth
ofthebeamandbis thebreadth ofthebeam,
41.4.2.1IfthenumericalvalueofM
l
asdefined
in41.4.2exceedsthe numerical valueofthe moment
A1
11
,longitudinalreinforcementshall beprovidedon
theflexural compression face,suchthatthe beam
canalsowithstandanequivalentM
e2
givenhy
M
e2==M,-M
u
'the moment
M~.2beingtakenas acung
in the opposite sense tothemomentM
u
'
41.4.~'TransverseReinforcement
Twoleggedclosedhoopsenclosingthecorner
longitudinalbarsshallhaveanareaofcross-section
A~\"givenby
A :::;_ 7:JSV + Vusv _..
svhili
l
(O.H7j~) 2.5eft((J.~7./;) ,
hut the total transverse reinforcement shall notbeless
than
(f\.e-fc.lb.s,.
0.87J~
where
"1:, torsionalmoment,
'<I_.shearforce,
s,.=spacing of thestirrupreinforcement.
b .~.centre-to-centredistance hctwccnCtuner
i
bars inthedirectionofthewidth.
d,0-centre-to-centredistancebetweencorner
bars,
h- breadthofthemember,
t,.-characteristicstrengthofthestirrup
reinforcement,
t
w
-equivalentshearstressasspecifiedin
41.3.1,and
'(...-shearstrengthoftheconcreteasrt.~rTable
It).
42LIMITSTATI~OFSF:RVll~EABII.4IT\':
nE:I~~I.lE<.:'rl ON
42.1FlexuralMembers
In allnormalcases.thedeflectionofaflexuralmember
will
notheexcessiveifthe ratio of its
spanto its
effectivedepth is notgreaterthanappropriateratios
givenin23.2.1.Whendeflectionsarccalculutcd
accordingtoAnnexC,
theyshallnotexceedthe
permissiblevalues given in 23.2.
75
whichisafunctionofactualshearandtorsion.
41.1.1Thedesignruleslaiddownin 41.3 and 41.4
shallapplyto beams of solid rectangularcross..section.
However, theseclausesmayalso be appliedtoflanged
beams,bysubstituting b
w
forbin which casetheyare
generally conservative;thereforespecialist literature
maybereferred to.
41.2CriticalSection
Sectionslocatedless than adistance d.from theface
ofthesupportmaybedesignedforthesametorsionas
computed at a distanced,wheredis theeffectivedepth.
41.3ShearandTorsion
41.3.1EquivalentShear
Equivalentshear,V
c
'
shall becalculatedfrom the
formula:
where
V
=equivalent.shear,
,"
V=
shear,
u
1·=torsionalmoment,and
u
b= breadthofbeam,
The equivalentnominalshearstress.'tv...in thiscase
shallbecalculatedasgivenin40.1,exceptfor
substituting\'uhyV
c
'The values ofrvcshallnotexceed
thevaluesoftt'mallgiveninTable20.
41.3.2 If the equivalentnominalshearstress,'t\'l'docs
notexceedtl'givenin.ablc19,minimumshear
reinforcementshallhe providedasper26.5.1.6.
41.3.3Iftv\.exceedst,giveninTable19.both
longitudinal andtransversereinforcementshallhe
provided inaccordancewith41.4.
41.4Reinforcementin MembersSubjectedto
Torsion
41.4.1 Reinforcementfortorsion,when
required,shall
consistof longitudinalandtransversereinforcement,
41.4.2LongitudinalReinforcement
The
longitudinalreinforcementshall
hedesignedto
resistan equivalent bending1l10111Cnl,M
d
-givenby
M
d
=M
u
+M,
where
M
u=bending moment at thecross-section,and
M.=t:(.I+!Jlb·)
u 1.7
IS456:2000
where
'~Iisthetorsionalmoment,Dis the overalldepth
ofthebeamandbis thebreadth ofthebeam,
41.4.2.1IfthenumericalvalueofM
l
asdefined
in41.4.2exceedsthe numerical valueofthe moment
A1
11
,longitudinalreinforcementshall beprovidedon
theflexural compression face,suchthatthe beam
canalsowithstandanequivalentM
e2
givenhy
M
e2==M,-M
u
'the moment
M~.2beingtakenas acung
in the opposite sense tothemomentM
u
'
41.4.~'TransverseReinforcement
Twoleggedclosedhoopsenclosingthecorner
longitudinalbarsshallhaveanareaofcross-section
A~\"givenby
A :::;_ 7:JSV + Vusv _..
svhili
l
(O.H7j~) 2.5eft((J.~7./;) ,
hut the total transverse reinforcement shall notbeless
than
(f\.e-fc.lb.s,.
0.87J~
where
"1:, torsionalmoment,
'<I_.shearforce,
s,.=spacing of thestirrupreinforcement.
b .~.centre-to-centredistance hctwccnCtuner
i
bars inthedirectionofthewidth.
d,0-centre-to-centredistancebetweencorner
bars,
h- breadthofthemember,
t,.-characteristicstrengthofthestirrup
reinforcement,
t
w
-equivalentshearstressasspecifiedin
41.3.1,and
'(...-shearstrengthoftheconcreteasrt.~rTable
It).
42LIMITSTATI~OFSF:RVll~EABII.4IT\':
nE:I~~I.lE<.:'rl ON
42.1FlexuralMembers
In allnormalcases.thedeflectionofaflexuralmember
will
notheexcessiveifthe ratio of its
spanto its
effectivedepth is notgreaterthanappropriateratios
givenin23.2.1.Whendeflectionsarccalculutcd
accordingtoAnnexC,
theyshallnotexceedthe
permissiblevalues given in 23.2.
75
IS456:2000
•
43LIMITSTATE OFSERVICEABILITY:
CRACKING
43.1FlexuralMembers
In general,compliancewith the spacingrequirements
ofreinforcementgiven
in
26.3.2should be sufficient
to controlflexuralcracking. Ifgreaterspacingare
required,theexpectedcrack widthshouldbechecked
byformula given in AnnexF.
"I)
43.2CompressionMembers
Cracks due to bending in a compression member
subjectedto a design axialload greaterthanO.2fc...A
c
'
where
I"is the characteristiccompressivestrength of
Jet
concrete andA
c
is the area of the gross section of the
member,neednotbechecked.Amembersubjectedto
lesserloadthan0.2letA
c
maybeconsidered
asflexuralmemberfor thepurposeofcrackcontrol
(see43.1).
•
43LIMITSTATE OFSERVICEABILITY:
CRACKING
43.1FlexuralMembers
In general,compliancewith the spacingrequirements
ofreinforcementgiven
in
26.3.2should be sufficient
to controlflexuralcracking. Ifgreaterspacingare
required,theexpectedcrack widthshouldbechecked
byformula given in AnnexF.
"I)
43.2CompressionMembers
Cracks due to bending in a compression member
subjectedto a design axialload greaterthanO.2fc...A
c
'
where
I"is the characteristiccompressivestrength of
Jet
concrete andA
c
is the area of the gross section of the
member,neednotbechecked.Amembersubjectedto
lesserloadthan0.2letA
c
maybeconsidered
asflexuralmemberfor thepurposeofcrackcontrol
(see43.1).
IS456:ZOOO
ANNEXA
(Clause2)
LIST OF REFERREDINDIANSTANDARDS
IS No.
269 : 1989
383 :
1970
432 (Part 1) :
1982
4SS:1989
516 :19S9
875
(Part 1) : 1987
(Part 2) :t987
(Part 3) : 1987
(Part 4) : 1987
(PartS): 1987
1199:1959
1343 : 1980
1489
(Part1) : 1991
(Part2) :
1991
1566 : 1982
1641:1988
nIle
Specificationforordinary
Portlandcement,33grade(fourth
revision)
Specificationfor coarseand fine
aggregates from natural sources
for concrete(secondrevision)
Specification for mild steel and
medium tensile steel bars and
hard-drawnsteelwire for
concrete reinforcement: Part 1
Mild steel and medium tensile
steel bars
(third
revision)
Specificationfor Portland slag
cement(fourthrevision)
Method of test for strength of
concrete
Codeof practicefordesignloads
(otherthanearthquake)for
buildingsand structures:
Deadloads - Unit weights of
building
materialandstored
materials
(second
revision)
Imposedloads (second revision)
Windloads(second revision)
Snowloads(second revision)
Specialloadsand load
combinations(secondrevision)
Methodsofsamplingand
analysis
of concrete
Code of practice for
prestressed
concrete(first revision)
SpecificationforPortland
pozzolana
cement:
Fly ash based(thirdrevision)
Calcinedclaybased (third
revision)
Specificationfor hard-drawn
steelwire fabricforconcrete
reinforcement
(secondrevision)
Code ofpracticefor firesafety
of buildings(general): General
principles of fire grading and
classification
(firstrevision)
ISNo.
1642:1989
1186: 1985
1791:1968
1893: 1984
1904: 1986
2062 : 1992
2386 (Part 3) :
1963
2502: 1963
2S05:1980
2506:1985
2514 : 1963
2751: 1979
3025
(Part 17) : 1984
(Part 18) : 1984
77
ntle
Codeofpracticeforfiresafety
ofbuildings(aenn):Detailsof
construction(firstI'tvilio1l)
Specification for high strength
deformedsteelbarsandwiresfor
concretereinforcement(third
m'uioll)
Specificationfor batchtype
concretemixers(StCoMrevision)
Criteria forearthquakeresistant
designofstructures(fourth
nvision)
Code of practice fordesignand
construction of
foundationsin
soils :Generalrequirements(thirdrevision)
Steelforgeneralstructural
purposes(fourthTn'uion)
Methodsoftestforaggreptesfor
concrete:
Part3Specific
pavity,
density, voids, absorption and
bulking
Codeof practiceforbendingand
fixingofbarsforconcrete
reinforcement
Concretevibrators-Immersion
type -Generalrequirements
Generalrequirementsforscreed
board concrete vibrators(first
revision)
Specificationforconcrete
vibratingtables
Recommendedpracticeforweldingofmild steelplain and
deformed bars forreinforced
construction
(firstTn'ision)
Methods of sampling and test
(physicalandchemical)forwater
and waste water:
Non-filterableresidue(total
suspendedsolids)
(first
~vision)
Volatileand fixed residue (total
filterableandnon-filterable)
(first
revision)
ANNEXA
(Clause2)
LIST OF REFERREDINDIANSTANDARDS
IS No.
269 : 1989
383 :
1970
432 (Part 1) :
1982
4SS:1989
516 :19S9
875
(Part 1) : 1987
(Part 2) :t987
(Part 3) : 1987
(Part 4) : 1987
(PartS): 1987
1199:1959
1343 : 1980
1489
(Part1) : 1991
(Part2) :
1991
1566 : 1982
1641:1988
nIle
Specificationforordinary
Portlandcement,33grade(fourth
revision)
Specificationfor coarseand fine
aggregates from natural sources
for concrete(secondrevision)
Specification for mild steel and
medium tensile steel bars and
hard-drawnsteelwire for
concrete reinforcement: Part 1
Mild steel and medium tensile
steel bars
(third
revision)
Specificationfor Portland slag
cement(fourthrevision)
Method of test for strength of
concrete
Codeof practicefordesignloads
(otherthanearthquake)for
buildingsand structures:
Deadloads - Unit weights of
building
materialandstored
materials
(second
revision)
Imposedloads (second revision)
Windloads(second revision)
Snowloads(second revision)
Specialloadsand load
combinations(secondrevision)
Methodsofsamplingand
analysis
of concrete
Code of practice for
prestressed
concrete(first revision)
SpecificationforPortland
pozzolana
cement:
Fly ash based(thirdrevision)
Calcinedclaybased (third
revision)
Specificationfor hard-drawn
steelwire fabricforconcrete
reinforcement
(secondrevision)
Code ofpracticefor firesafety
of buildings(general): General
principles of fire grading and
classification
(firstrevision)
ISNo.
1642:1989
1186: 1985
1791:1968
1893: 1984
1904: 1986
2062 : 1992
2386 (Part 3) :
1963
2502: 1963
2S05:1980
2506:1985
2514 : 1963
2751: 1979
3025
(Part 17) : 1984
(Part 18) : 1984
77
ntle
Codeofpracticeforfiresafety
ofbuildings(aenn):Detailsof
construction(firstI'tvilio1l)
Specification for high strength
deformedsteelbarsandwiresfor
concretereinforcement(third
m'uioll)
Specificationfor batchtype
concretemixers(StCoMrevision)
Criteria forearthquakeresistant
designofstructures(fourth
nvision)
Code of practice fordesignand
construction of
foundationsin
soils :Generalrequirements(thirdrevision)
Steelforgeneralstructural
purposes(fourthTn'uion)
Methodsoftestforaggreptesfor
concrete:
Part3Specific
pavity,
density, voids, absorption and
bulking
Codeof practiceforbendingand
fixingofbarsforconcrete
reinforcement
Concretevibrators-Immersion
type -Generalrequirements
Generalrequirementsforscreed
board concrete vibrators(first
revision)
Specificationforconcrete
vibratingtables
Recommendedpracticeforweldingofmild steelplain and
deformed bars forreinforced
construction
(firstTn'ision)
Methods of sampling and test
(physicalandchemical)forwater
and waste water:
Non-filterableresidue(total
suspendedsolids)
(first
~vision)
Volatileand fixed residue (total
filterableandnon-filterable)
(first
revision)
IS456:1000
ISNo.
(Part 22) : 1986
(Part 23) : 1986
(Part 24) :
1986
(Part 32) : 1988
3414 : 1968
3812 :
1981
395I (Part 1):.
1975
403I(PartS):
1988
4082 : 1996
4326:1993
4656:1968
4845 : 1968
4925:1968
4926:1976
S816:1999
6061
(Part 1) :1971
(Part 2) :1971
6452:1989
6461
(PartJ) :1972
(Part2) : 1972
Title
Acidity(firstrevision)
Alkalinity(firstrevision)
Sulphates(firstrevision)
Chloride(firstrevision)
Code of practice for design and
installationofjoints in buildings
Specificationfor
flyash for use
aspozzolanaandadmixture(first
revision)
Specificationforhollowclaytiles
for floorsand roofs: Part 1Filler
type
(firstrevision)
Methods of physical tests for
hydraulic
cement : Part
S
Determinationof initialandfinal
setting times(firstrevision)
Recommendations on stacking
andstorage
ofconstruction
materialsandcomponentsat site
(second revision)
Codeof practice for earthquake
resistantdesignandconstruction
of buildings
(secondrevision)
Specificationfor form vibrators
for concrete
Definitionsandterminology
relating to hydrauliccement
Specificationforconcrete
hatchingand mixing plant
Specification for ready-mixed
concrete
(secondrevision)
Methodoftestforsplitting
tensilestrength
ofconcrete(firstrevision)
Codeof practiceforconstruction
of floor and roof withjoists and
filler blocks:
Withhollowconcretefiller
blocks
With hollow clay filler blocks
(firstrevision)
Specification for high alumina
cement for structuraluse
Glossary
oftermsrelatingto
cement:
Concrete aggregates
Materials
ISNo.
(Part 3) : 1972
(Part 4) :1972
(Part
S):1972
(Part 6) :1972
(Part 7) : 1973
(Part 8) :
1973
(Part 9) : 1973
(Part10) :
1973
(Part
11) :1973
(Part 12): 1973
6909:1990
7861
(Part 1) :
1975
(Part 2) : 1975
8041: 1990
8043:1991
8112:1989
9013 : 1978
9103 :
1999
9417 : 1989
11817: 1986
12089: 1987
12119:1981
78
Title
Concretereinforcement
Typesof concrete
Pormworkfor concrete
Equipment,tool and plant
Mixing,laying,compaction,
curing and otherconstruction
aspect
Properties
ofconcrete
Structuralaspects
Testsand testing apparatus
Prestressedconcrete
Miscellaneous
Specificationforsupersulphated
cement
Code of practice for extreme
weatherconcreting :
Recommendedpractice for hot
weatherconcreting
Recommendedpractice for cold
weatherconcreting
Specificationfor rapidhardening
Portlandcement(second
revision)
Specification for hydrophobic
Portlandcement(secondrevision)
Specificationfor 43grade
ordinary Portland cement(first
revision)
Methodofmaking,curing
anddeterminingcompressive
strengthofacceleratedcured
concrete test specimens
Specificationfor admixtures for
concrete
(first revisiom
Recommendations for welding
cold worked bars for reinforced
concreteconstruction
(j;rst
r~\lision)
Classificationof jointsin
buildingsforaccommodationof
dimensional deviations during
construction
Specificationfor granulatedslag
for manufactureof Portlandslag
cement
Generalrequirementsfor pan
mixers for concrete
ISNo.
(Part 22) : 1986
(Part 23) : 1986
(Part 24) :
1986
(Part 32) : 1988
3414 : 1968
3812 :
1981
395I (Part 1):.
1975
403I(PartS):
1988
4082 : 1996
4326:1993
4656:1968
4845 : 1968
4925:1968
4926:1976
S816:1999
6061
(Part 1) :1971
(Part 2) :1971
6452:1989
6461
(PartJ) :1972
(Part2) : 1972
Title
Acidity(firstrevision)
Alkalinity(firstrevision)
Sulphates(firstrevision)
Chloride(firstrevision)
Code of practice for design and
installationofjoints in buildings
Specificationfor
flyash for use
aspozzolanaandadmixture(first
revision)
Specificationforhollowclaytiles
for floorsand roofs: Part 1Filler
type
(firstrevision)
Methods of physical tests for
hydraulic
cement : Part
S
Determinationof initialandfinal
setting times(firstrevision)
Recommendations on stacking
andstorage
ofconstruction
materialsandcomponentsat site
(second revision)
Codeof practice for earthquake
resistantdesignandconstruction
of buildings
(secondrevision)
Specificationfor form vibrators
for concrete
Definitionsandterminology
relating to hydrauliccement
Specificationforconcrete
hatchingand mixing plant
Specification for ready-mixed
concrete
(secondrevision)
Methodoftestforsplitting
tensilestrength
ofconcrete(firstrevision)
Codeof practiceforconstruction
of floor and roof withjoists and
filler blocks:
Withhollowconcretefiller
blocks
With hollow clay filler blocks
(firstrevision)
Specification for high alumina
cement for structuraluse
Glossary
oftermsrelatingto
cement:
Concrete aggregates
Materials
ISNo.
(Part 3) : 1972
(Part 4) :1972
(Part
S):1972
(Part 6) :1972
(Part 7) : 1973
(Part 8) :
1973
(Part 9) : 1973
(Part10) :
1973
(Part
11) :1973
(Part 12): 1973
6909:1990
7861
(Part 1) :
1975
(Part 2) : 1975
8041: 1990
8043:1991
8112:1989
9013 : 1978
9103 :
1999
9417 : 1989
11817: 1986
12089: 1987
12119:1981
78
Title
Concretereinforcement
Typesof concrete
Pormworkfor concrete
Equipment,tool and plant
Mixing,laying,compaction,
curing and otherconstruction
aspect
Properties
ofconcrete
Structuralaspects
Testsand testing apparatus
Prestressedconcrete
Miscellaneous
Specificationforsupersulphated
cement
Code of practice for extreme
weatherconcreting :
Recommendedpractice for hot
weatherconcreting
Recommendedpractice for cold
weatherconcreting
Specificationfor rapidhardening
Portlandcement(second
revision)
Specification for hydrophobic
Portlandcement(secondrevision)
Specificationfor 43grade
ordinary Portland cement(first
revision)
Methodofmaking,curing
anddeterminingcompressive
strengthofacceleratedcured
concrete test specimens
Specificationfor admixtures for
concrete
(first revisiom
Recommendations for welding
cold worked bars for reinforced
concreteconstruction
(j;rst
r~\lision)
Classificationof jointsin
buildingsforaccommodationof
dimensional deviations during
construction
Specificationfor granulatedslag
for manufactureof Portlandslag
cement
Generalrequirementsfor pan
mixers for concrete
ISNo. Title ISNo.
12269:1981 Specificationfor S3grade(PanI):1992
ordinary Portlandcement
(Pan 2) :
t992
12330:1988 Specificationforsulphate
13920:
1'993
resisting Portland cement
12600:1989 Specificationfor low heat
Portland
cement
13311 Methodsofnon-destructive14687 : 1999
testing of concrete:
79
IS456:
1000
Title
Ultrasonicpulse velocity
Rebound
hammer
Codeofpracticeforductile
detailing of reinforced concrete
structures subjected to seesmic
forces
Guidelinesforfalseworkfor
concretestructures
12269:1981 Specificationfor S3grade(PanI):1992
ordinary Portlandcement
(Pan 2) :
t992
12330:1988 Specificationforsulphate
13920:
1'993
resisting Portland cement
12600:1989 Specificationfor low heat
Portland
cement
13311 Methodsofnon-destructive14687 : 1999
testing of concrete:
79
IS456:
1000
Title
Ultrasonicpulse velocity
Rebound
hammer
Codeofpracticeforductile
detailing of reinforced concrete
structures subjected to seesmic
forces
Guidelinesforfalseworkfor
concretestructures
IS456:2000
ANNEX B
(Clauses18.2.2,22.3.1,22.7.26.2.1and 32.1)
STRUCTURAL DESIGN(WORKINGSTRESSMETHOD)
8-1GENERAL
B-l.1GeneralDesilnRequirements
The general designrequirementsof Section 3 shall
applyto thisAnnex.
0-1.2RedistributionofMoments
Exceptwherethesimplifiedanalysisusingcoefficients
(see22.5) is used, themomentsoverthesupport"for
any assumedarrangementof loading,includingthe
deadload
momentsmayeachbeincreasedordecreased
hynotmore than15percent,providedthatthese
modifiedmomentsover the supportsare used for the
calculationof thecorresponding
momentsinthespans,
8-1.3AssumptionsforDesilDofMembers
In the methods basedonelastictheory,thefollowing
assumptionsshall be made:
illAtanycross-section. plane sections before
bendingremainplain afterbending.
b) All
tensilestressesarc takenupbyreinforcement
and nonebyconcrete.except as otherwise
specificallypermitted.
c) Thestress-strainrelationship
ofsteeland
concrete,underworkingloads,is a
straightline.
d) Themodularratiomhas the value280.
30'cbc
whereac~hcispermissiblecompressive stressdue
tobendingin concretein N/mm
2
asspecifiedin
Table21.
NOTE-
Theexpressiongiven formpanially takes into
account long-termeffectssuchascreep.Therefore thisIn
is notthesameWithemodularratioderivedbDSC~don the
valueofEf:givenin6.2.3.1.
B-2PERMISSIBLESTRESSES
B-2.1PermL.sibleStresses inConcrete
Permissiblestressesfor the variousgradesof concrete
shallhetaken asthosegivenin Tables21uno23.
NOTE - For increase instrengthwithQie6.1.1shall be
upplicable.Thevaluesofpermissiblestres~shallhenbruinedhy
interpolationbetweenthegradesofconcrete.
B-2.1.1DirectTension
Formembersin direct tension, when full tension is
takenbythereinforcementalone,thetensilestressshall
be not greater than the valuesgiven below:
Grad«
til M I()
COlif,.,It
T",I.fUtStress,1.2
Nllnlll'
MI~
2.0
M20
2.8
M2~
3.2
M~O
3,6
M3~
4.0
M40
4.4
M4~
4.8
M~O
~.2
F
f
Thetensilestress shallbecalculatedas
A".+mA.t
where
F
L=totaltensionon thememberminuspre
tensioninsteel.ifany,beforeconcreting:
A\:=cross-sectionalareaot'concreteexcludina
anyfinishingmaterial andrcinforcina
stee]:
n,==modularratio:and
A..=cross-sectionalareaofreinforcingsteel
intension.
n-1.1.%Bond StressforDeformedBars
In thecaseof defannedbarsconformingto IS1786,
thebond stresses giveninTahle21maybeincreased
by 60percent.
80
0-2.2PermissibleStressesin Steel Reinforcement
Pennissiblcstresses in steel reinforcement shell not
exceedthe valuesspecifiedin Table22.
8-2.2.1Inflexuralmembersthevalueof0'..givenin
Table 22isapplicableat the centroid of the tensile
reinforcementsubjecttotheconditionthatwhenmore
thanonelayeroftensilereinforcementisprovided,
the stress at the centroid of the outermost layershall
notexceedbymorethan10percentthevaluegivenin
TobIe22.
8-2.3IncreaseinPermlaslbleStresla
Wherestressesduetowind(orearthquake)temperature
andshrinkageeffectsare combinedwiththosedue to
dead, live and impactload,thestressesspecified in
Tables21t22 and 23maybeexceeded upto a limit of
33.!.percent.Windandseismicforcesneed notbe
3
consideredasactingsimultaneously.
ANNEX B
(Clauses18.2.2,22.3.1,22.7.26.2.1and 32.1)
STRUCTURAL DESIGN(WORKINGSTRESSMETHOD)
8-1GENERAL
B-l.1GeneralDesilnRequirements
The general designrequirementsof Section 3 shall
applyto thisAnnex.
0-1.2RedistributionofMoments
Exceptwherethesimplifiedanalysisusingcoefficients
(see22.5) is used, themomentsoverthesupport"for
any assumedarrangementof loading,includingthe
deadload
momentsmayeachbeincreasedordecreased
hynotmore than15percent,providedthatthese
modifiedmomentsover the supportsare used for the
calculationof thecorresponding
momentsinthespans,
8-1.3AssumptionsforDesilDofMembers
In the methods basedonelastictheory,thefollowing
assumptionsshall be made:
illAtanycross-section. plane sections before
bendingremainplain afterbending.
b) All
tensilestressesarc takenupbyreinforcement
and nonebyconcrete.except as otherwise
specificallypermitted.
c) Thestress-strainrelationship
ofsteeland
concrete,underworkingloads,is a
straightline.
d) Themodularratiomhas the value280.
30'cbc
whereac~hcispermissiblecompressive stressdue
tobendingin concretein N/mm
2
asspecifiedin
Table21.
NOTE-
Theexpressiongiven formpanially takes into
account long-termeffectssuchascreep.Therefore thisIn
is notthesameWithemodularratioderivedbDSC~don the
valueofEf:givenin6.2.3.1.
B-2PERMISSIBLESTRESSES
B-2.1PermL.sibleStresses inConcrete
Permissiblestressesfor the variousgradesof concrete
shallhetaken asthosegivenin Tables21uno23.
NOTE - For increase instrengthwithQie6.1.1shall be
upplicable.Thevaluesofpermissiblestres~shallhenbruinedhy
interpolationbetweenthegradesofconcrete.
B-2.1.1DirectTension
Formembersin direct tension, when full tension is
takenbythereinforcementalone,thetensilestressshall
be not greater than the valuesgiven below:
Grad«
til M I()
COlif,.,It
T",I.fUtStress,1.2
Nllnlll'
MI~
2.0
M20
2.8
M2~
3.2
M~O
3,6
M3~
4.0
M40
4.4
M4~
4.8
M~O
~.2
F
f
Thetensilestress shallbecalculatedas
A".+mA.t
where
F
L=totaltensionon thememberminuspre
tensioninsteel.ifany,beforeconcreting:
A\:=cross-sectionalareaot'concreteexcludina
anyfinishingmaterial andrcinforcina
stee]:
n,==modularratio:and
A..=cross-sectionalareaofreinforcingsteel
intension.
n-1.1.%Bond StressforDeformedBars
In thecaseof defannedbarsconformingto IS1786,
thebond stresses giveninTahle21maybeincreased
by 60percent.
80
0-2.2PermissibleStressesin Steel Reinforcement
Pennissiblcstresses in steel reinforcement shell not
exceedthe valuesspecifiedin Table22.
8-2.2.1Inflexuralmembersthevalueof0'..givenin
Table 22isapplicableat the centroid of the tensile
reinforcementsubjecttotheconditionthatwhenmore
thanonelayeroftensilereinforcementisprovided,
the stress at the centroid of the outermost layershall
notexceedbymorethan10percentthevaluegivenin
TobIe22.
8-2.3IncreaseinPermlaslbleStresla
Wherestressesduetowind(orearthquake)temperature
andshrinkageeffectsare combinedwiththosedue to
dead, live and impactload,thestressesspecified in
Tables21t22 and 23maybeexceeded upto a limit of
33.!.percent.Windandseismicforcesneed notbe
3
consideredasactingsimultaneously.
Table21PermissibleStresses inConcrete
(ClausesB·l.3.B·2.1.B-2.l.2.B-2.3andB·4.2)
All values in Ntmm
l
.
IS456:2000
0.6
0.8
0.9
1.0
1.112
1.3
1.4
PermissibleStrea
In Bond(Averale)for
Plain Bars InTension
(4)
PermissibleStressInCompression
Bending Direct
(2) (3)
<,0"
3.0 2.5
5.0 4.0
7.0
5.0
8.5 6.0
10.0 8.0
11.5 lJ.O
13.0 10.0
14.5 11.0
16.0 t2.0
M 10
M
15
M20
M2S
M30
M35
M40
M45
M50
NOTES
I The values ofpermissible:shear stress in concretearegiven in Table 23.
2The bond stress given in col 4 shallbeincreasedby25percentforbarsin compression.
(1)
<Yrade01
Concrete
0=n
A=,.
B-3PERMISSIBLELOADS INCOMPRESSION
MEMBERS
B-3.1PedestalsandShortColumnswithLateral
Ties
The
axialloadPpermissible on a pedestal or short
column reinforced with longitudinal bars and lateral
ties shallnotexceedthat given by the following
equation:
where
permissible stress in concrete in direct
compression.
cross-sectionalareaofconcrete
excludinganyfinishingmaterial and
reinforcing steel.
0""=permissiblecompressivestressfor
column bars, and
A",=cross-sectional area of the longitudinal
steel.
NOTE - The minimumeccentricity mentioned in 25.4 may
he
deemedtobeincorporated intheaboveequanon.
B-3.2ShortColumnswith HelicalReinforcement
Thepermissibleload forcolumnswithhelical
reinforcementsatisfyingthe requirementof
39.4.1shallbe1.05 times the permissible load for similar member
with lateral ties or rings.
B-3.3 LongColumns
Themaximumpermissiblestressin areinforcedconcretecolumn or partthereofhaving a ratio of
effectivecolumn lengthtoleastlateraldimensionabove
12shallnotexceedthat whichresultsfrom the
multiplicationof theappropriatemaximumpermissible
stress as specified under
B-2.1and
B-2.2by the
coefficient C, given by the following formula:
C=1.25
_.!SL
r 48b
where
C,=reduction coefficient:
I",=effective length of column; and
b=leastlateral dimension of column; for
column with helical reinforcement,
bis
the diameter of the core.
For moreexact calculations,the maximum permissible
stresses in a reinforcedconcrete column or part thereof
havinga ratio ofeffective column length to least lateral
radius of gyration above 40 shall not exceed those
which result from the multiplication of the appropriate
maximum permissible stresses specified under
B.2.1
and0-2.2bythe coefficientC,given by the following
formula:
C
r
=1.25 _
le~
IbO'min
wherei
miP
is the least radius of gyration.
B-3.4CompositeColumns
a)Allowableload- The allowable axial loadP
on a composite column consisting of structural
steel or cast-iron column thoroughly encased in
concrete reinforced with both longitudinal and
spiral reinforcement.shall not exceed that given
hy the following
formula;
2116815/07-12
81
(ClausesB·l.3.B·2.1.B-2.l.2.B-2.3andB·4.2)
All values in Ntmm
l
.
IS456:2000
0.6
0.8
0.9
1.0
1.112
1.3
1.4
PermissibleStrea
In Bond(Averale)for
Plain Bars InTension
(4)
PermissibleStressInCompression
Bending Direct
(2) (3)
<,0"
3.0 2.5
5.0 4.0
7.0
5.0
8.5 6.0
10.0 8.0
11.5 lJ.O
13.0 10.0
14.5 11.0
16.0 t2.0
M 10
M
15
M20
M2S
M30
M35
M40
M45
M50
NOTES
I The values ofpermissible:shear stress in concretearegiven in Table 23.
2The bond stress given in col 4 shallbeincreasedby25percentforbarsin compression.
(1)
<Yrade01
Concrete
0=n
A=,.
B-3PERMISSIBLELOADS INCOMPRESSION
MEMBERS
B-3.1PedestalsandShortColumnswithLateral
Ties
The
axialloadPpermissible on a pedestal or short
column reinforced with longitudinal bars and lateral
ties shallnotexceedthat given by the following
equation:
where
permissible stress in concrete in direct
compression.
cross-sectionalareaofconcrete
excludinganyfinishingmaterial and
reinforcing steel.
0""=permissiblecompressivestressfor
column bars, and
A",=cross-sectional area of the longitudinal
steel.
NOTE - The minimumeccentricity mentioned in 25.4 may
he
deemedtobeincorporated intheaboveequanon.
B-3.2ShortColumnswith HelicalReinforcement
Thepermissibleload forcolumnswithhelical
reinforcementsatisfyingthe requirementof
39.4.1shallbe1.05 times the permissible load for similar member
with lateral ties or rings.
B-3.3 LongColumns
Themaximumpermissiblestressin areinforcedconcretecolumn or partthereofhaving a ratio of
effectivecolumn lengthtoleastlateraldimensionabove
12shallnotexceedthat whichresultsfrom the
multiplicationof theappropriatemaximumpermissible
stress as specified under
B-2.1and
B-2.2by the
coefficient C, given by the following formula:
C=1.25
_.!SL
r 48b
where
C,=reduction coefficient:
I",=effective length of column; and
b=leastlateral dimension of column; for
column with helical reinforcement,
bis
the diameter of the core.
For moreexact calculations,the maximum permissible
stresses in a reinforcedconcrete column or part thereof
havinga ratio ofeffective column length to least lateral
radius of gyration above 40 shall not exceed those
which result from the multiplication of the appropriate
maximum permissible stresses specified under
B.2.1
and0-2.2bythe coefficientC,given by the following
formula:
C
r
=1.25 _
le~
IbO'min
wherei
miP
is the least radius of gyration.
B-3.4CompositeColumns
a)Allowableload- The allowable axial loadP
on a composite column consisting of structural
steel or cast-iron column thoroughly encased in
concrete reinforced with both longitudinal and
spiral reinforcement.shall not exceed that given
hy the following
formula;
2116815/07-12
81
IS456:2000
Table22PermissibleStressesinSteelReinforcement
(Clauses8-2.2, 8-2.2.1,B-2.3andB..4.2)
SI
No.
TypeofStressIn Steel
Reinforcement
PermissibleStressesInN/mm
2
(l) l2)
i)Tension (0"1or011)
a)LJp(0andincluding
20mm
b) Over 20 rom
ii)Compressionin column
bars(all)
Mild SteelBan
Conformingto
GradeI of
IS4J2(Pan I)
(3)
140I
130
130
MediumTensile
SteelConform
ing to IS 432
(Port 1)
(4)
Halftheguaranteed
yieldstress subject
to amaximumof190
130
High YieldStrength
DeformedBarsCon
formingtoIS 1786
(Grade Fe41S)
(5)
230
230
190
iii)Compressioninbarsin a
bean)orslab when thecom
pressiveresistanceof the
concrete istakenintoaccount
Thecalculatedcompressive stressinthesurroundingconcrete multipliedby1.Stimes
themodularratio or0.:whicheveris lower
iv) Compressionin bars in a
beam or slab where the
compressiveresistance
of the
concreteis not
taken into account:
a)Up
toandincluding
20mm
b)Over20mm
140I
130
Halftheguaranteed
yieldstress subject
to a
maximumof190
190
J90
NOTES
1 For
highyieldstrengthdeformedbars of Grade FeSOOthepermissiblestress indirecttensionandflexuraltensionshallbeOj~.f~.
The permissiblestressesfor shear andcompressionreinforcementshallbeasfor GradeFe415.
1For welded wire fabric conformingto IS156fl,thepermissiblevalueintensionCJIIIis 230Nzmm'.
3Forthepurpose of this standard,the yieldstressof steels for whichthereisnoclearlydefinedyieldpointshouldbetaken tobe
0.2percentproofstress.
4 When mildsteelconformingtoGrade II of IS 432(PartI) is used,thepermissiblestressesshallbe90 percent of the permissible
stressesin col 3,orifthedesigndetailshave alreadybeenworkedout on thebasisofmildsteelconformingto GradeI of IS432(Pan
I);theareaofreinforcementshallbeincreasedby10percentofthatrequired forGrodeIsteel.
A=
~(.'
(J=
~.
A=
m
(J=
cc
20percentofthe gross area of thecolumn.If a
hollowmetalcoteis used, it shall be filled with
concrete.The amountof longitudinaland spiral
reinforcementandtherequirementsastospacing
ofbars,detailsofsplicesandthicknessof
protectiveshelloutsidethespiral,shallconform
to require- rnents of16.5.3.A clearance of at
least 75mmshall bemaintainedbetweenthe
spiral and the metal core at aJl points,except
that when the core consists of a structural steel
H-column, the minimumclearancemay be
reduced to 50 mrn,
c)Splicesand
connectionsofmetalcores- Metal
cores in compositecolumns shall be accurately
milledatsplicesand positive provisions shall
bemadeforalignmentofonecoreaboveanother.At thecolumnbase.provisionsshall be
(J=
me
permissible stress in concrete in direct
compression:
At"=netareaofconcretesection; which is
equalto thegrossarea oftheconcrete
section -A
IC
-Am;
permissiblecompressivestressfor
columnbars;
cross-sectional area of longitudinal bar
reinforcement;
allowableunit
stressin metalcore, not to
exceed
125N/mm
2
for a steel core, or
70
N/mm
2
for acastiron core; and
thecross-sectionalareaof thesteel or
cast
iron core.
b)Metalcoreandreinforcement- Thecross
sectionalareaofthemetalcore shallnotexceed
where
82
Table22PermissibleStressesinSteelReinforcement
(Clauses8-2.2, 8-2.2.1,B-2.3andB..4.2)
SI
No.
TypeofStressIn Steel
Reinforcement
PermissibleStressesInN/mm
2
(l) l2)
i)Tension (0"1or011)
a)LJp(0andincluding
20mm
b) Over 20 rom
ii)Compressionin column
bars(all)
Mild SteelBan
Conformingto
GradeI of
IS4J2(Pan I)
(3)
140I
130
130
MediumTensile
SteelConform
ing to IS 432
(Port 1)
(4)
Halftheguaranteed
yieldstress subject
to amaximumof190
130
High YieldStrength
DeformedBarsCon
formingtoIS 1786
(Grade Fe41S)
(5)
230
230
190
iii)Compressioninbarsin a
bean)orslab when thecom
pressiveresistanceof the
concrete istakenintoaccount
Thecalculatedcompressive stressinthesurroundingconcrete multipliedby1.Stimes
themodularratio or0.:whicheveris lower
iv) Compressionin bars in a
beam or slab where the
compressiveresistance
of the
concreteis not
taken into account:
a)Up
toandincluding
20mm
b)Over20mm
140I
130
Halftheguaranteed
yieldstress subject
to a
maximumof190
190
J90
NOTES
1 For
highyieldstrengthdeformedbars of Grade FeSOOthepermissiblestress indirecttensionandflexuraltensionshallbeOj~.f~.
The permissiblestressesfor shear andcompressionreinforcementshallbeasfor GradeFe415.
1For welded wire fabric conformingto IS156fl,thepermissiblevalueintensionCJIIIis 230Nzmm'.
3Forthepurpose of this standard,the yieldstressof steels for whichthereisnoclearlydefinedyieldpointshouldbetaken tobe
0.2percentproofstress.
4 When mildsteelconformingtoGrade II of IS 432(PartI) is used,thepermissiblestressesshallbe90 percent of the permissible
stressesin col 3,orifthedesigndetailshave alreadybeenworkedout on thebasisofmildsteelconformingto GradeI of IS432(Pan
I);theareaofreinforcementshallbeincreasedby10percentofthatrequired forGrodeIsteel.
A=
~(.'
(J=
~.
A=
m
(J=
cc
20percentofthe gross area of thecolumn.If a
hollowmetalcoteis used, it shall be filled with
concrete.The amountof longitudinaland spiral
reinforcementandtherequirementsastospacing
ofbars,detailsofsplicesandthicknessof
protectiveshelloutsidethespiral,shallconform
to require- rnents of16.5.3.A clearance of at
least 75mmshall bemaintainedbetweenthe
spiral and the metal core at aJl points,except
that when the core consists of a structural steel
H-column, the minimumclearancemay be
reduced to 50 mrn,
c)Splicesand
connectionsofmetalcores- Metal
cores in compositecolumns shall be accurately
milledatsplicesand positive provisions shall
bemadeforalignmentofonecoreaboveanother.At thecolumnbase.provisionsshall be
(J=
me
permissible stress in concrete in direct
compression:
At"=netareaofconcretesection; which is
equalto thegrossarea oftheconcrete
section -A
IC
-Am;
permissiblecompressivestressfor
columnbars;
cross-sectional area of longitudinal bar
reinforcement;
allowableunit
stressin metalcore, not to
exceed
125N/mm
2
for a steel core, or
70
N/mm
2
for acastiron core; and
thecross-sectionalareaof thesteel or
cast
iron core.
b)Metalcoreandreinforcement- Thecross
sectionalareaofthemetalcore shallnotexceed
where
82
B-4MEMBERSSUBJECTEDTOCOMBINED
AXIALLOADANDBENDING
8-4.1DesignBasedon UnerackedSection
A member subjected to axial load and bending (due to
eccentricity of load. monolithic construction, lateral
forces,
etc)shall be considered safe provided the
followingconditions
aresatisfied:
made to transfer the load to the footing at safe
unit stresses in accordancewith34.The baseof
the metal section shall be designed to transfer
the load from the entire composite columns to
the footing. or it
maybe designed to transfer
the load from the metal section only. provided
it is placed inthe pieror pedestal as toleave
ample section of concrete above the base for the
transfer of load from the reinforced concrete
section of the column
bymeans of bond on the
vertical
reinforcementandbydirect
compressionon the
concrete.Transferof loads
to the metal core shall be provided forbythe
useof bearingmembers,suchasbillets,brackets
orotherpositive connections, these shall be
provided at
thetop oft.hemetal core and at
intermediate floor levels where required. The
column as a wholeshallsatisfytherequirements
of formula given under (a) atany point;in
addition to this, the reinforced concrete portion
shall be designed
tocarry, according toa-3.1
or
B-3.2as the casemaybe, all floor loads
brought into the column at levels between the
metal brackets or connections. In
applyingthe
formulae under B-3.1 or8-3.2the grossarea of
columnshallbe taken to be the area of the
concretesection outside the metal core, and the
aJlowableloadonthereinforcedconcretesection
shall be further limited to0.28.t::ktimes gross
sectional
area ofthe colurnn.
d)Allowable Load on Metal Core Only- The
metal core ofcompositecolumnsshall be
designed to carry safely any construction or
other
loadsto be placed upon them priorto their
encasement inconcrete.
a)
aCt,cal+(1chc,cal~1.
ace. 0cbc
IS456:2000
b)TIleresultanttensionin concrete is not greater
than35
percentand 25 percentof the resultant
compressionfor biaxial and uniaxial bending
respectively,or does notexceedthree-fourths,
the 7
daymodulusofrupture of concrete.
NOTES
P
1
a= forcolumnswithtieswhereP.A.and
lu.•1A,.+1.5mA-.. '
A...definedin B-3.1andmis the modularratio.
M
2O'l.huIII:::ZwhereMequals themomentandZequals
modulusofsection.In thecaseof sectionssubjecttomoments
in twodirections,the stress shallbecalculatedseparatelynod
addedalgebraically.
8-4.2DesignBasedon CrackedSection
Iftherequirementsspecifiedin8-4.1arenotsatisfied,
the stresses in concrete and steel shall be calculated
bythetheoryof cracked section in which the tensile
resistance of concrete is ignored. If the calculated
stresses
are withinthepermissiblestress specified in
Tables21, 22 and 23 the section
maybeassumedto be
safe.
NOTE- Themaximum
stressin concreteandsteelmaybe
foundfromtablesandchartsbasedon thecrackedsectiontheory
ordirectlybydeterminingtheno..stresslinewhichshouldsatisfy
the
followingrequirements:
a)The direct load shouldhe equal to thealgebraicsum of
theforceson concreteandsteel,
b) Themomentof theexternal loads aboutanyreference
lineshouldbeequalto thealgebraicsumofthemoment
of theforcesincancrete(ignoringthetensile force in
concrete)andsteelaboutthesameli~."and
c) Themoment ofthe externalloadsabout any other
referencelinesshouldbe equal to the algebraicsum of
themOlneft1oftheforcesinconcrete(ignoringthetensile
forceinconcrete)and steel aboutthesame line.
B4.3MembersSubjectedtoCombinedDirect
LoadandFlexure
Memberssubjectedtocombineddirectloadandflexure
and shallbedesignedbylimitslatemethod as in39.5
afterapplyingappropriateloadfactorsasgiveninTable
18.
B-SSHEAR
where
ace,e,l!=calculateddirect compressive stress
inconcrete,
<T
ce
=permissibleaxialcompressivestress
in concrete,
ach~,f.~aal=calculatedbendingcompressive
stress in concrete, and
ache=permissiblebendingcompressive
stress inconcrete.
B-S.lNominal ShearStress
The nominal shear stressrin beams or slabsof
v
unifonn depth shallbecalculatedbythe following
equation:
V
t
v= -
bel
where
V=shear force due to design loads,
83
AXIALLOADANDBENDING
8-4.1DesignBasedon UnerackedSection
A member subjected to axial load and bending (due to
eccentricity of load. monolithic construction, lateral
forces,
etc)shall be considered safe provided the
followingconditions
aresatisfied:
made to transfer the load to the footing at safe
unit stresses in accordancewith34.The baseof
the metal section shall be designed to transfer
the load from the entire composite columns to
the footing. or it
maybe designed to transfer
the load from the metal section only. provided
it is placed inthe pieror pedestal as toleave
ample section of concrete above the base for the
transfer of load from the reinforced concrete
section of the column
bymeans of bond on the
vertical
reinforcementandbydirect
compressionon the
concrete.Transferof loads
to the metal core shall be provided forbythe
useof bearingmembers,suchasbillets,brackets
orotherpositive connections, these shall be
provided at
thetop oft.hemetal core and at
intermediate floor levels where required. The
column as a wholeshallsatisfytherequirements
of formula given under (a) atany point;in
addition to this, the reinforced concrete portion
shall be designed
tocarry, according toa-3.1
or
B-3.2as the casemaybe, all floor loads
brought into the column at levels between the
metal brackets or connections. In
applyingthe
formulae under B-3.1 or8-3.2the grossarea of
columnshallbe taken to be the area of the
concretesection outside the metal core, and the
aJlowableloadonthereinforcedconcretesection
shall be further limited to0.28.t::ktimes gross
sectional
area ofthe colurnn.
d)Allowable Load on Metal Core Only- The
metal core ofcompositecolumnsshall be
designed to carry safely any construction or
other
loadsto be placed upon them priorto their
encasement inconcrete.
a)
aCt,cal+(1chc,cal~1.
ace. 0cbc
IS456:2000
b)TIleresultanttensionin concrete is not greater
than35
percentand 25 percentof the resultant
compressionfor biaxial and uniaxial bending
respectively,or does notexceedthree-fourths,
the 7
daymodulusofrupture of concrete.
NOTES
P
1
a= forcolumnswithtieswhereP.A.and
lu.•1A,.+1.5mA-.. '
A...definedin B-3.1andmis the modularratio.
M
2O'l.huIII:::ZwhereMequals themomentandZequals
modulusofsection.In thecaseof sectionssubjecttomoments
in twodirections,the stress shallbecalculatedseparatelynod
addedalgebraically.
8-4.2DesignBasedon CrackedSection
Iftherequirementsspecifiedin8-4.1arenotsatisfied,
the stresses in concrete and steel shall be calculated
bythetheoryof cracked section in which the tensile
resistance of concrete is ignored. If the calculated
stresses
are withinthepermissiblestress specified in
Tables21, 22 and 23 the section
maybeassumedto be
safe.
NOTE- Themaximum
stressin concreteandsteelmaybe
foundfromtablesandchartsbasedon thecrackedsectiontheory
ordirectlybydeterminingtheno..stresslinewhichshouldsatisfy
the
followingrequirements:
a)The direct load shouldhe equal to thealgebraicsum of
theforceson concreteandsteel,
b) Themomentof theexternal loads aboutanyreference
lineshouldbeequalto thealgebraicsumofthemoment
of theforcesincancrete(ignoringthetensile force in
concrete)andsteelaboutthesameli~."and
c) Themoment ofthe externalloadsabout any other
referencelinesshouldbe equal to the algebraicsum of
themOlneft1oftheforcesinconcrete(ignoringthetensile
forceinconcrete)and steel aboutthesame line.
B4.3MembersSubjectedtoCombinedDirect
LoadandFlexure
Memberssubjectedtocombineddirectloadandflexure
and shallbedesignedbylimitslatemethod as in39.5
afterapplyingappropriateloadfactorsasgiveninTable
18.
B-SSHEAR
where
ace,e,l!=calculateddirect compressive stress
inconcrete,
<T
ce
=permissibleaxialcompressivestress
in concrete,
ach~,f.~aal=calculatedbendingcompressive
stress in concrete, and
ache=permissiblebendingcompressive
stress inconcrete.
B-S.lNominal ShearStress
The nominal shear stressrin beams or slabsof
v
unifonn depth shallbecalculatedbythe following
equation:
V
t
v= -
bel
where
V=shear force due to design loads,
83
IS456:2000
B-S.Z.l.1For solid slabs thepermissibleshear stress
in concrete shall
be
kf
c
wherekhas the valueliven
below:
Ovemlldepth300ar2752SO22S200175150(1"
ofslab,mmmore less
k 1.001.051.101.1S1.201.251.30
8-5.2.3WithShearReinforcement
Whenshearreinforcementisprovidedthe nominal
shearstressf
c
in beamsshall notexceedf
c
.....givenin
Table 24.
NOTE- This doesnotapplytol1atslabsforwhich31-'shall
apply.
8-5.2.2ShearStrengthofMembersUnderAxial
Compression
For members subjected to axialcompression P.
the permissible shear stressinconcretet
c
given
in Table 23, shalt
bemultipliedbythe following
factor:
~=1+~' but not exceeding 1.5
A.fc:k
axialcompressiveforce inN,
grossareaoftheconcretesectionin mm',
and
characteristic compressive strength of
concrete.
where
p
=
A,=
Ie...=
v±Mlanfj
f= d
v bd
where
t
y
'V,banddare the sameas in B-5.1,
M=bendingmomentat the section,and
~=anglebetween the top and the bottom
edges of thebeam.
The negative sign in the formula applies when the
bendingmoment
Mincreasesnumericallyinthesame
directionas theeffectivedepth dincreases,and the
positivesign whenthe momentdecreasesnumerically
in this direction.
b=breadthof themember,whichforflanged
sections shall be taken as the breadth of
the web, and
d= effective
depth.
B-S.l.1BeamsofVaryingDepth
In the case of beams of varying depth, the equation
shall bemodifiedas:
8-5.2DesignShearStrengthorConcrete
8-S.2.1Thepermissibleshearstressinconcrete in
beamswithoutshearreinforcementisgiveninTable23.
Table23PermissibleShearStressinConcrete
(ClausesB-2.1,B-2.3,8-4.2,8-5.2.1,B-S.2.2,B-s.3,B-S.4,8..5.5.1,8.5.5.3,B·6.~.2.B-6.3.3 and8-6.4.3 andTabl~21)
l00~ PermissibleShearStressinConcrete,t
c
'N/mm
J
bd
GradeofConcrete
MIS M20 M2S M30 M3S M40
andabove
(I) (2) (3) (4) (S) (6) (7)
SO.IS 0.18 0.18 0.19 0.20 0.20 0.20
0.25 0.22 0.220.23 0.23 0.23 0.23
O.SO 0.29 0.30 0.31 0.31 0.31 0.32
0.7S 0.34 0.3S 0,36 0.37 0.37 0.38
1.00 0.37 0.39 0.40 0.41 0.42 0.42
1.25 0.40 0.42 0.44 0.45 0.45 0.46
1.50 0.42 0.45 0.46 0.48 0.49 0.49
1.7~ 0.44 0.47 0.49 O.SO 0.520.52
2.00 0.44 0.49 O.SI 0.53 0.'4 O.SS
2.25 0.44 0.51 0.~3 o.~s 0.'6 0.57
2.S0 0.44 0.51 0.55 0.S7 o.sa 0.60
2.7S 0.44 0.51 0.56 0.58 0.60 0.62
3.00and 0.44 o.s: 0.S7 0.60 0.61 0.63
above
NOTE-A.is thatareaoflongitudinaltensionreinforcclncntwhichcontinuesatleastoneeffedivcdeplh beyondthelettianbeiDI
consideredexceptatsupport.~wherethefullareaoftensionreinforcementmaybeusedprovidedthedetai1inlconfotmlto26.2.2and
26.2.3.
84
B-S.Z.l.1For solid slabs thepermissibleshear stress
in concrete shall
be
kf
c
wherekhas the valueliven
below:
Ovemlldepth300ar2752SO22S200175150(1"
ofslab,mmmore less
k 1.001.051.101.1S1.201.251.30
8-5.2.3WithShearReinforcement
Whenshearreinforcementisprovidedthe nominal
shearstressf
c
in beamsshall notexceedf
c
.....givenin
Table 24.
NOTE- This doesnotapplytol1atslabsforwhich31-'shall
apply.
8-5.2.2ShearStrengthofMembersUnderAxial
Compression
For members subjected to axialcompression P.
the permissible shear stressinconcretet
c
given
in Table 23, shalt
bemultipliedbythe following
factor:
~=1+~' but not exceeding 1.5
A.fc:k
axialcompressiveforce inN,
grossareaoftheconcretesectionin mm',
and
characteristic compressive strength of
concrete.
where
p
=
A,=
Ie...=
v±Mlanfj
f= d
v bd
where
t
y
'V,banddare the sameas in B-5.1,
M=bendingmomentat the section,and
~=anglebetween the top and the bottom
edges of thebeam.
The negative sign in the formula applies when the
bendingmoment
Mincreasesnumericallyinthesame
directionas theeffectivedepth dincreases,and the
positivesign whenthe momentdecreasesnumerically
in this direction.
b=breadthof themember,whichforflanged
sections shall be taken as the breadth of
the web, and
d= effective
depth.
B-S.l.1BeamsofVaryingDepth
In the case of beams of varying depth, the equation
shall bemodifiedas:
8-5.2DesignShearStrengthorConcrete
8-S.2.1Thepermissibleshearstressinconcrete in
beamswithoutshearreinforcementisgiveninTable23.
Table23PermissibleShearStressinConcrete
(ClausesB-2.1,B-2.3,8-4.2,8-5.2.1,B-S.2.2,B-s.3,B-S.4,8..5.5.1,8.5.5.3,B·6.~.2.B-6.3.3 and8-6.4.3 andTabl~21)
l00~ PermissibleShearStressinConcrete,t
c
'N/mm
J
bd
GradeofConcrete
MIS M20 M2S M30 M3S M40
andabove
(I) (2) (3) (4) (S) (6) (7)
SO.IS 0.18 0.18 0.19 0.20 0.20 0.20
0.25 0.22 0.220.23 0.23 0.23 0.23
O.SO 0.29 0.30 0.31 0.31 0.31 0.32
0.7S 0.34 0.3S 0,36 0.37 0.37 0.38
1.00 0.37 0.39 0.40 0.41 0.42 0.42
1.25 0.40 0.42 0.44 0.45 0.45 0.46
1.50 0.42 0.45 0.46 0.48 0.49 0.49
1.7~ 0.44 0.47 0.49 O.SO 0.520.52
2.00 0.44 0.49 O.SI 0.53 0.'4 O.SS
2.25 0.44 0.51 0.~3 o.~s 0.'6 0.57
2.S0 0.44 0.51 0.55 0.S7 o.sa 0.60
2.7S 0.44 0.51 0.56 0.58 0.60 0.62
3.00and 0.44 o.s: 0.S7 0.60 0.61 0.63
above
NOTE-A.is thatareaoflongitudinaltensionreinforcclncntwhichcontinuesatleastoneeffedivcdeplh beyondthelettianbeiDI
consideredexceptatsupport.~wherethefullareaoftensionreinforcementmaybeusedprovidedthedetai1inlconfotmlto26.2.2and
26.2.3.
84
a) For vertical stirrups
~=G.vAsvSiDex
where
A=
sv
~~y=
t=c
b=
8-5.2.3.1 For slabs,T
yshall notexceedhalf the value
off
t
malgiven in Table 24.
B-S.3Minimum ShearReinforcement
Whent
yis less thant
c
given in Table 23. minimum
shear reinforcement shall be provided inaccordance
with26.5.1.6.
B-5.4 Design ofShearReinforcement
Whentvexceedst,giveninTable23,shear
reinforcementshall beprovidedin anyof thefollowing
forms:
a)Verticalstirrups,
b) Bent-up bars along with stirrups. and
c)Inclinedstirrups.
Where bent-up bars arc provided, theircontribution
towards shearresistance.shall not be morethan half
that of the total shearreinforcement.
Shearreinforcementshall
beprovided tocarrya shear
equaltoV-
'tc.bd.The strengthofshearreinforcement
Vshall be calculated as below:
!'
v=O'svAsvd
s
Sv
h) For inclined stirrups or a series of bars bent..up
atdifferentcross-sections:
~=C1
sv~vd(sina+cosa)
Sv
c)Forsingle bar or single group of parallel bars,
all bent-upatthe same cross-section:
totalcross-sectionalareaof stirrup legs
or bent-up bars withina distance,
spacing of the stirrups or bent-upbars
along the length of the
member,
design shear strength of theconcrete,
breadthofthememberwhichfor
flanged beams, shall be taken as the
breadth of the web b
wt
(J"y=permissibletensilestress inshear
reinforcementwhichshallnot be taken
IS456:2000
greater than
230N/mn1
2
,
ex=angle between the inclined stirrupor
bent-up bar andtheaxis ofthemember,
not less than45
u
•
and
d=effective depth.
Nf)TE--Wheremort.thanonetypeofshearreinforcementis
used to reinforce thesameportion of the beam.theIota)shear
resistanceshall be computedasthe sumoftheresistanceforthe
varioustypesseparately.Thearea of thestirrupsshall notbe
lessthan the minimumspecifiedin 26.5.1.6.
8-5.5EnhancedShearStrengthof Sections Close
toSupports
8-S.5.1General
Shearfailure
atsectionsofbeamsandcantilevers
without shearreinforcementwillnormallyoccuron
planeinclinedat anangle30"to the horizontal. If the
angle of failure
plane
isforced to~cinclinedmore
steeplythanthisIbecause the section considered
(X- X)inFig. 24iscloseto a support or forother
reasons],the shear forcerequiredto produce failure is
increased.
Theenhancementof shearstrength
maybe taken
into account in the design ofsections
nearasupport
hyincreasingdesign shearstrengthofconcrete,',.
to2dr/a,.providedthat the designshearstress at
the face ofsupportremainsless than thevalues
given in Table 23.Account
maybe taken of
the
enhancementin anysituationwhere thesection
considerediscloserto the face of asupportof
concentratedloadthan twice theeffectivedepth, d.
To be effective, tensionreinforcementshouldextend
on each side of the point where
itisintersectedhya
possible failure plane for a distance. at least equal to
theeffectivedepth,or beprovidedwith
an
equivalentanchorage.
8-5.5.2Shear ReinforcementforSectionsCloseto
Supports
If shearreinforcementisrequired,the totalareaofthis
is givenby:
A"=avb(f
v
..2dfJav)/O.87fy~O.4a
v
b/O.R~f)
This reinforcement should beprovidedwithin the
middle three quarters ofavoWhereQ
v
is less than.l.
horizontal shear reinforcement will be more effective
thanvertical.
Table24MaximumShearStress,"rma.'N/mm
1
(Clauses8-5.2.3. 8·5.2.3.t,8..5.5,1andB-6.3.1)
ConcreteGrade
\'m••'N/mm
1
M)~
1.6
M20
1.8
M2~
1.9
85
MJO
2.2 2.J
~140 andabove
2.5
~=G.vAsvSiDex
where
A=
sv
~~y=
t=c
b=
8-5.2.3.1 For slabs,T
yshall notexceedhalf the value
off
t
malgiven in Table 24.
B-S.3Minimum ShearReinforcement
Whent
yis less thant
c
given in Table 23. minimum
shear reinforcement shall be provided inaccordance
with26.5.1.6.
B-5.4 Design ofShearReinforcement
Whentvexceedst,giveninTable23,shear
reinforcementshall beprovidedin anyof thefollowing
forms:
a)Verticalstirrups,
b) Bent-up bars along with stirrups. and
c)Inclinedstirrups.
Where bent-up bars arc provided, theircontribution
towards shearresistance.shall not be morethan half
that of the total shearreinforcement.
Shearreinforcementshall
beprovided tocarrya shear
equaltoV-
'tc.bd.The strengthofshearreinforcement
Vshall be calculated as below:
!'
v=O'svAsvd
s
Sv
h) For inclined stirrups or a series of bars bent..up
atdifferentcross-sections:
~=C1
sv~vd(sina+cosa)
Sv
c)Forsingle bar or single group of parallel bars,
all bent-upatthe same cross-section:
totalcross-sectionalareaof stirrup legs
or bent-up bars withina distance,
spacing of the stirrups or bent-upbars
along the length of the
member,
design shear strength of theconcrete,
breadthofthememberwhichfor
flanged beams, shall be taken as the
breadth of the web b
wt
(J"y=permissibletensilestress inshear
reinforcementwhichshallnot be taken
IS456:2000
greater than
230N/mn1
2
,
ex=angle between the inclined stirrupor
bent-up bar andtheaxis ofthemember,
not less than45
u
•
and
d=effective depth.
Nf)TE--Wheremort.thanonetypeofshearreinforcementis
used to reinforce thesameportion of the beam.theIota)shear
resistanceshall be computedasthe sumoftheresistanceforthe
varioustypesseparately.Thearea of thestirrupsshall notbe
lessthan the minimumspecifiedin 26.5.1.6.
8-5.5EnhancedShearStrengthof Sections Close
toSupports
8-S.5.1General
Shearfailure
atsectionsofbeamsandcantilevers
without shearreinforcementwillnormallyoccuron
planeinclinedat anangle30"to the horizontal. If the
angle of failure
plane
isforced to~cinclinedmore
steeplythanthisIbecause the section considered
(X- X)inFig. 24iscloseto a support or forother
reasons],the shear forcerequiredto produce failure is
increased.
Theenhancementof shearstrength
maybe taken
into account in the design ofsections
nearasupport
hyincreasingdesign shearstrengthofconcrete,',.
to2dr/a,.providedthat the designshearstress at
the face ofsupportremainsless than thevalues
given in Table 23.Account
maybe taken of
the
enhancementin anysituationwhere thesection
considerediscloserto the face of asupportof
concentratedloadthan twice theeffectivedepth, d.
To be effective, tensionreinforcementshouldextend
on each side of the point where
itisintersectedhya
possible failure plane for a distance. at least equal to
theeffectivedepth,or beprovidedwith
an
equivalentanchorage.
8-5.5.2Shear ReinforcementforSectionsCloseto
Supports
If shearreinforcementisrequired,the totalareaofthis
is givenby:
A"=avb(f
v
..2dfJav)/O.87fy~O.4a
v
b/O.R~f)
This reinforcement should beprovidedwithin the
middle three quarters ofavoWhereQ
v
is less than.l.
horizontal shear reinforcement will be more effective
thanvertical.
Table24MaximumShearStress,"rma.'N/mm
1
(Clauses8-5.2.3. 8·5.2.3.t,8..5.5,1andB-6.3.1)
ConcreteGrade
\'m••'N/mm
1
M)~
1.6
M20
1.8
M2~
1.9
85
MJO
2.2 2.J
~140 andabove
2.5
IS456:2000
8-5.5.3Enhanced Shear Strength Near Supports
(Simplified Approach)
TheproceduregiveninD-S.S.land8-5.5.2maybe
usedfor allbeams. Howeverforbeamscarrying
generallyuniform load orwheretheprincipalloadis
located
furtherthan 2dfromtheface ofsupport,the
shear stressmaybecalculatedatasection a distanced
fromthefaceof support.The valueoft
c
iscalculated
inaccordancewith Table 23 andappropriateshear
reinforcementis providedatsectionscloserto the
support, no furthercheckfor suchsectionisrequired.
8-6TORSION
8-6.1General
In structures where torsion isrequiredto maintain
equilibrium, members shallbedesignedfor torsion in
accordancewith8-6.2, 8-6.3 and 0-6.4.However,for
suchindeterminatestructureswhere torsion can be
eliminatedby releasingredundentrestraints,no
specificdesignfortorsionisnecessaryprovided
torsional stiffness isneglectedinthecalculation of
internal forces.Adequatecontrol ofanytorsional
cracking is provided by the shear reinforcement as
perB-S.
NOTE- The approachto
designinthisclause for torsionis as
follows:
Torsional reinforcement is not calculated separately from
thatrequired for bendingandshear.Instead thetotal
longitudinal reinforcement is determined fornfictitious
bending moment which is a function of actual bending
moment and
torsion;similarly web reinforcement is
determinedfor afictitiousshearwhichisIlfunctionofIlCtual
shear and torsion.
8-6.1.1Thedesignrules laiddownin8·6.3
and8-6.4shallapplyto beams of solidrectangular
cross-section.However,theseclausesmayalso be
appliedto
flanged beamsbysubstitutingb
wforb,in
whichcasethey are generallyconservative;therefore
specialist
literaturemaybereferredto.
B-6.2CriticalSection
Sectionslocatedless than adistanced.from the face
of thesupportmaybedesignedfor the same torsionas
computedat adistance d,wheredis theeffective
depth,
B-6.3ShearandTorsion
B-6.3.1EquivalentShear
Equivalentshear,V
e
shallbecalculated from the
formula:
v=V+1.6 T •
• b
where
~=equivalentshear,
v=shear.
T=torsionalmoment,and
b=breadth of beam.
Theequivalentnominalshear stress,'Ye'in this case
shalJ be calculated asgiyen in B-5.1,exceptfor
substitutingV byV
e
•
Thevaluesof
1'vcshallnotexceed
the
valuesof
'cmaxgivenin'fable24.
B-6.3.2If the equivalentnominal shear stress'ryedoes
not exceedfe'given in Table23.minimum shear
reinforcement
shallbeprovidedasspecified
in26.5.1.6.
8-6.3.3If
1'yeexceeds1'\;given inTable23,both
longitudinalandtransverse reinforcement shall be
providedinaccordance with B-6.4.
8-6.4ReinforcementinMembersSubjectedto
Torsion
B-6.4.1Reinforcementfor torsion,whenrequired,
shallconsistoflongitudinalandtransverse
reinforcement.
B-6.4.2
LongitudinalReinforcement
Thelongitudinalreinforcement shall be designed to
resist an equivalent bending moment,
M
r l
,givenby
Mel:::M+M
r
where
M=bendingmoment at the cross-section, and
(J+D/b)
M
l
=T1.7,whereTis the torsional
moment,
Dis the overall depth of the
beam andbis thebreadthof the beam.
B-6.4.2.1If thenumericalvalue of M
l
asdefined
in8-6.4.2exceedsthe numerical
valueof themoment
M
tlongitudinalreinforcernentshall be provided on
theflexuralcompressionface, such that the beamcan
alsowithstandan equivalentmomentMt.2givenbyM
ez=Ml-M,
the momentM
e2
being taken as acting in
theoppositesense to the moment
M.
8-6.4.3TransverseReinforcement
Two leggedclosedhoopsenclosingthecorner
longitudinalbars shall have an area ofcross-sectionA.
y
'givenby
A T,s; V'Svb h I-,v="+ tutte tota
bId)(Jay2.5d
1
(J,v
transversereinforcementshall notbeless than
(tv.-tc)b.sy
a.v
where
T=torsionalmoment.
V=shear force.
86
8-5.5.3Enhanced Shear Strength Near Supports
(Simplified Approach)
TheproceduregiveninD-S.S.land8-5.5.2maybe
usedfor allbeams. Howeverforbeamscarrying
generallyuniform load orwheretheprincipalloadis
located
furtherthan 2dfromtheface ofsupport,the
shear stressmaybecalculatedatasection a distanced
fromthefaceof support.The valueoft
c
iscalculated
inaccordancewith Table 23 andappropriateshear
reinforcementis providedatsectionscloserto the
support, no furthercheckfor suchsectionisrequired.
8-6TORSION
8-6.1General
In structures where torsion isrequiredto maintain
equilibrium, members shallbedesignedfor torsion in
accordancewith8-6.2, 8-6.3 and 0-6.4.However,for
suchindeterminatestructureswhere torsion can be
eliminatedby releasingredundentrestraints,no
specificdesignfortorsionisnecessaryprovided
torsional stiffness isneglectedinthecalculation of
internal forces.Adequatecontrol ofanytorsional
cracking is provided by the shear reinforcement as
perB-S.
NOTE- The approachto
designinthisclause for torsionis as
follows:
Torsional reinforcement is not calculated separately from
thatrequired for bendingandshear.Instead thetotal
longitudinal reinforcement is determined fornfictitious
bending moment which is a function of actual bending
moment and
torsion;similarly web reinforcement is
determinedfor afictitiousshearwhichisIlfunctionofIlCtual
shear and torsion.
8-6.1.1Thedesignrules laiddownin8·6.3
and8-6.4shallapplyto beams of solidrectangular
cross-section.However,theseclausesmayalso be
appliedto
flanged beamsbysubstitutingb
wforb,in
whichcasethey are generallyconservative;therefore
specialist
literaturemaybereferredto.
B-6.2CriticalSection
Sectionslocatedless than adistanced.from the face
of thesupportmaybedesignedfor the same torsionas
computedat adistance d,wheredis theeffective
depth,
B-6.3ShearandTorsion
B-6.3.1EquivalentShear
Equivalentshear,V
e
shallbecalculated from the
formula:
v=V+1.6 T •
• b
where
~=equivalentshear,
v=shear.
T=torsionalmoment,and
b=breadth of beam.
Theequivalentnominalshear stress,'Ye'in this case
shalJ be calculated asgiyen in B-5.1,exceptfor
substitutingV byV
e
•
Thevaluesof
1'vcshallnotexceed
the
valuesof
'cmaxgivenin'fable24.
B-6.3.2If the equivalentnominal shear stress'ryedoes
not exceedfe'given in Table23.minimum shear
reinforcement
shallbeprovidedasspecified
in26.5.1.6.
8-6.3.3If
1'yeexceeds1'\;given inTable23,both
longitudinalandtransverse reinforcement shall be
providedinaccordance with B-6.4.
8-6.4ReinforcementinMembersSubjectedto
Torsion
B-6.4.1Reinforcementfor torsion,whenrequired,
shallconsistoflongitudinalandtransverse
reinforcement.
B-6.4.2
LongitudinalReinforcement
Thelongitudinalreinforcement shall be designed to
resist an equivalent bending moment,
M
r l
,givenby
Mel:::M+M
r
where
M=bendingmoment at the cross-section, and
(J+D/b)
M
l
=T1.7,whereTis the torsional
moment,
Dis the overall depth of the
beam andbis thebreadthof the beam.
B-6.4.2.1If thenumericalvalue of M
l
asdefined
in8-6.4.2exceedsthe numerical
valueof themoment
M
tlongitudinalreinforcernentshall be provided on
theflexuralcompressionface, such that the beamcan
alsowithstandan equivalentmomentMt.2givenbyM
ez=Ml-M,
the momentM
e2
being taken as acting in
theoppositesense to the moment
M.
8-6.4.3TransverseReinforcement
Two leggedclosedhoopsenclosingthecorner
longitudinalbars shall have an area ofcross-sectionA.
y
'givenby
A T,s; V'Svb h I-,v="+ tutte tota
bId)(Jay2.5d
1
(J,v
transversereinforcementshall notbeless than
(tv.-tc)b.sy
a.v
where
T=torsionalmoment.
V=shear force.
86
t=\'('
't=
\
s=
spacing of the stirrup reinforcement,
v
hi=
centre-to-centredistancebetweencorner
bars inthedirection of the width,
ri.
::::centre-to-centredistance betweencorner
bars in the direction of the depth,
b:::breadthofthemember,
87
IS456:2000
0',"v=perInissibIe tc nsi1estrcssinshe ar
reinforcement,
equivalent
shearstress as specified in
8-6.3.J.,and
shearstrengthof the concrete
asspecified
in'fable23.
't=
\
s=
spacing of the stirrup reinforcement,
v
hi=
centre-to-centredistancebetweencorner
bars inthedirection of the width,
ri.
::::centre-to-centredistance betweencorner
bars in the direction of the depth,
b:::breadthofthemember,
87
IS456:2000
0',"v=perInissibIe tc nsi1estrcssinshe ar
reinforcement,
equivalent
shearstress as specified in
8-6.3.J.,and
shearstrengthof the concrete
asspecified
in'fable23.
IS456:2000
ANNEXC
(Clauses22.3.2,23.2.1and42.1)
CALCULATIONOF DEFLECTION
Col TOTALDEFLECTION
C-I.lThetotaldeflectionshallbetakenasthesumof
theshort-termdeflectiondeterminedinaccordance
withC-2 and the
long-termdeflection,inaccordance
with
C-)and
C-4.
C-2SHORT-TERM DEFLECTION
C-2.1 Theshort-term
deflectionmaybecalculatedby
the
usualmethodsfor elasticdeflectionsusing the
short-term
modulusofelasticityofconcrete,
E(and
an effective moment of inertialeffgiven by the
followingequation:
I
where
I,=momentof inertiaof thecrackedsection,
ferI"
M,=crackingmoment,equalto where
Yt
I.,is themodulusofruptureofconcrete,
I
g
,is themomentofinertiaof the gross
sectionabout thecentroidalaxis,
neglectingthe
reinforcement,andY,isthe
distance from centroidal axis of gross
section.
neglectingthereinforcement,to
extremefibreintension.
M=maximummomentunderserviceloads,
z=leverarm.
.r=depthofneutralaxis.
d=effectivedepth.
bw=breadthof web.and
b=breadthofcompressionface.
Forcontinuousbeams,deflectionshaJlbecalculated
using the values ofIt'lit'and M
r
modified by the
followingequation:
[
XI
+
Xl]( )
Xe=k.2+I -klXo
where
X
e=modifiedvalueofX,
XI'Xl=valuesofXat thesupports,
XII=valueofXat midspan,
k,=coefficientgivenin Table2S,and
X=valueofIt'I"orM
r
asappropriate.
C-3 DEFLECTION DUETO SHRINKAGE
C-3.! Thedeflectiondue toshrinkagea..maybe
computedfromthefollowingequation:
ae.=k3Y'cs1
2
where
k,is aconstantdependinguponthesuppon
.conditions,
O.Sforcantilevers,
0.125for
simplysupportedmembers.
0.086formemberscontinuousat oneend,
and
0.063for
fullycontinuousmembers.
e
v;isshrinkagecurvatureequalto
k.=t
wheref:
ea
is theultimateshrinkagestrainofconcrete
(Set6.2.4).
k.=0.72xP,~s1.0for0.25sP.-Pc< 1.0
1',
=0.65x1',~s1.0forPI-r,~1.0
1',
Table2SValuesofCoefficient,k,
(ClauseC-2.1)
0.5or less
o
NOTE -*1is givenby
where
0.6
0.03
0.7
0.08
0.8
0.16
0.9
0.30
1.0
0.50
J.I
0.73
1.2
0.91
1.3
0.97
1.4
1.0
MI'M!=supportmoments.lind
M
f
, .
M,.!=lixedendmomenta.
88
ANNEXC
(Clauses22.3.2,23.2.1and42.1)
CALCULATIONOF DEFLECTION
Col TOTALDEFLECTION
C-I.lThetotaldeflectionshallbetakenasthesumof
theshort-termdeflectiondeterminedinaccordance
withC-2 and the
long-termdeflection,inaccordance
with
C-)and
C-4.
C-2SHORT-TERM DEFLECTION
C-2.1 Theshort-term
deflectionmaybecalculatedby
the
usualmethodsfor elasticdeflectionsusing the
short-term
modulusofelasticityofconcrete,
E(and
an effective moment of inertialeffgiven by the
followingequation:
I
where
I,=momentof inertiaof thecrackedsection,
ferI"
M,=crackingmoment,equalto where
Yt
I.,is themodulusofruptureofconcrete,
I
g
,is themomentofinertiaof the gross
sectionabout thecentroidalaxis,
neglectingthe
reinforcement,andY,isthe
distance from centroidal axis of gross
section.
neglectingthereinforcement,to
extremefibreintension.
M=maximummomentunderserviceloads,
z=leverarm.
.r=depthofneutralaxis.
d=effectivedepth.
bw=breadthof web.and
b=breadthofcompressionface.
Forcontinuousbeams,deflectionshaJlbecalculated
using the values ofIt'lit'and M
r
modified by the
followingequation:
[
XI
+
Xl]( )
Xe=k.2+I -klXo
where
X
e=modifiedvalueofX,
XI'Xl=valuesofXat thesupports,
XII=valueofXat midspan,
k,=coefficientgivenin Table2S,and
X=valueofIt'I"orM
r
asappropriate.
C-3 DEFLECTION DUETO SHRINKAGE
C-3.! Thedeflectiondue toshrinkagea..maybe
computedfromthefollowingequation:
ae.=k3Y'cs1
2
where
k,is aconstantdependinguponthesuppon
.conditions,
O.Sforcantilevers,
0.125for
simplysupportedmembers.
0.086formemberscontinuousat oneend,
and
0.063for
fullycontinuousmembers.
e
v;isshrinkagecurvatureequalto
k.=t
wheref:
ea
is theultimateshrinkagestrainofconcrete
(Set6.2.4).
k.=0.72xP,~s1.0for0.25sP.-Pc< 1.0
1',
=0.65x1',~s1.0forPI-r,~1.0
1',
Table2SValuesofCoefficient,k,
(ClauseC-2.1)
0.5or less
o
NOTE -*1is givenby
where
0.6
0.03
0.7
0.08
0.8
0.16
0.9
0.30
1.0
0.50
J.I
0.73
1.2
0.91
1.3
0.97
1.4
1.0
MI'M!=supportmoments.lind
M
f
, .
M,.!=lixedendmomenta.
88
whereP=~andP=~
'bd c·bd
andDisthe totaldepthof thesection,andIis the
lengthofspan.
C-4DEFLECTIONDUE TOCREEP
C-4.1The creep deflection due to permanent loads
a maybeobtained from thefollowingequation:
L'C(fICI'II')
2116818/07-13
89
IS456:2000
where
a =initial pluscreep deflectiondue to
i.cc(pmn)
permanentloads obtained using an
elastic
analysiswith an effective
modulus of elasticity,
E=
~.9beingthecreepcoefficient,
ce 1+8'
and
ai(.,erm)=short-termdeflectiondue to
permanentload usingE
c
•
'bd c·bd
andDisthe totaldepthof thesection,andIis the
lengthofspan.
C-4DEFLECTIONDUE TOCREEP
C-4.1The creep deflection due to permanent loads
a maybeobtained from thefollowingequation:
L'C(fICI'II')
2116818/07-13
89
IS456:2000
where
a =initial pluscreep deflectiondue to
i.cc(pmn)
permanentloads obtained using an
elastic
analysiswith an effective
modulus of elasticity,
E=
~.9beingthecreepcoefficient,
ce 1+8'
and
ai(.,erm)=short-termdeflectiondue to
permanentload usingE
c
•
IS456:2000
ANNEXD
(Clauses24.4and37.1.2)
SLABSSPANNINGINTWO DIRECTIONS
o-iRESTRAINEDSLABS
1)-1.0 When the comersof aslabarepreventedfrom
lifting,the slab mayhedesignedas specifiedinD-I.l
toD-l.11.
D-1.1Themaximumbendingmomentsperunitwidth
in a slab are givenbythefollowingequations:
u,=a
xwi;
M:::(Xwl
2
y )'x
where
u.and<Xyart:coefficientsgiven in Table 26,
w=totaldesign loadperunit area,
M.,My=moments on strips of unit width
spanning
I.and
lyrespectively,
and
IandI=lengths of the shorter span and
, y
longerspanrespectively.
D-l.2Slabsareconsideredalldividedineachdirection
intomiddlestrips andedgestripsas shown in Fig.25
themiddlestrip beingthree-quartersof the widthand
eachedgestrip one-eightof the width,
0-1.3Themaximummoment...calculatedas in0.1.1
applyonly to the middle strips and noredistribution
shall
bemade.
{)-1.4 Tensionreinforcementprovidedatmid-spaninthemiddle strip shall extend in the lower part of the
slabtowithin 0.25I ofacontinuousedge,orO.J5lof
adiscontinuousedge.
0-1.5Over the continuous edges of a middle strip,
thetensionreinforcementshallextendintheupper p,art
of the
slaba distanceofO.J51fromthesupport.and at
least
50perceentshall extend a distanceof0.3I.
D-I.6Atadiscontinuousedge,negativemomentsmay
arise. Theydepend on the
degreeoffixityat the~ge
of theslabbut,ingeneral,tensionreinforcement equal
toSOpercentof that providedat mid-spanextending
0.1Iinto the span willbesufficient.
D-t.7Reintorcementin edge strip, parallel to that
edge,shallcomplywiththeminimumgiveninSection
3andlhp.requirements for torsion given inD-t.S
to1)..1.10.
D·UITorsionreinforcementshall beprovidedat any
corner where the slab is simply supported on both
edges meetingatthat comer. It shall consist of top
and bottomreinforcement,each with layers of bars
placed parallelto the sides of the slab and extending
from the edges
aminimumdistance of one-fifth of
theshorterspan.Theareaofreinforcementin each of
thesefour layers shall bethree-quartersof the area
required for
themaximummid-span moment in the
slab.
0-1.9Torsion reinforcement equal
tohalf that
described in
D-t.Sshall be provided atacorner
containedbyedgesover only oneof whichthe slab is
continuous.
D-l.tO
Torsionreinforcementsneed not be provided
at any comer containedby edges over both of which
the slab iscontinuous.
D-1.11Torsion
VI.isgreaterthan2,theslabsshall
bedesignedas spanningone way.
0-2SIMPLYSUPPORTEDSLABS
D-Z.1When simply supported slabs do not have
adequateprovisionto resist torsionat comers and to
preventthecornersfromlifting,the maximum
I
•
I
1E0G
1ST
I
I
I
MIOOLESTRIP
,_.--t:t---Ir Ly -,
ri l"------!'!!'!.~---~-. ~
~T-' ~ .1
l
--Ii ..... MIOOL.ISTRP .+,
L-----.-sToi-----~
-i1~ oJ-Ly-----Jjl-
25AFORSPAN~ 258FORSPAN~
PIO.25DIVISIONOfSLABIN1UMIDl>LEAND EOOESTRIPS
90
ANNEXD
(Clauses24.4and37.1.2)
SLABSSPANNINGINTWO DIRECTIONS
o-iRESTRAINEDSLABS
1)-1.0 When the comersof aslabarepreventedfrom
lifting,the slab mayhedesignedas specifiedinD-I.l
toD-l.11.
D-1.1Themaximumbendingmomentsperunitwidth
in a slab are givenbythefollowingequations:
u,=a
xwi;
M:::(Xwl
2
y )'x
where
u.and<Xyart:coefficientsgiven in Table 26,
w=totaldesign loadperunit area,
M.,My=moments on strips of unit width
spanning
I.and
lyrespectively,
and
IandI=lengths of the shorter span and
, y
longerspanrespectively.
D-l.2Slabsareconsideredalldividedineachdirection
intomiddlestrips andedgestripsas shown in Fig.25
themiddlestrip beingthree-quartersof the widthand
eachedgestrip one-eightof the width,
0-1.3Themaximummoment...calculatedas in0.1.1
applyonly to the middle strips and noredistribution
shall
bemade.
{)-1.4 Tensionreinforcementprovidedatmid-spaninthemiddle strip shall extend in the lower part of the
slabtowithin 0.25I ofacontinuousedge,orO.J5lof
adiscontinuousedge.
0-1.5Over the continuous edges of a middle strip,
thetensionreinforcementshallextendintheupper p,art
of the
slaba distanceofO.J51fromthesupport.and at
least
50perceentshall extend a distanceof0.3I.
D-I.6Atadiscontinuousedge,negativemomentsmay
arise. Theydepend on the
degreeoffixityat the~ge
of theslabbut,ingeneral,tensionreinforcement equal
toSOpercentof that providedat mid-spanextending
0.1Iinto the span willbesufficient.
D-t.7Reintorcementin edge strip, parallel to that
edge,shallcomplywiththeminimumgiveninSection
3andlhp.requirements for torsion given inD-t.S
to1)..1.10.
D·UITorsionreinforcementshall beprovidedat any
corner where the slab is simply supported on both
edges meetingatthat comer. It shall consist of top
and bottomreinforcement,each with layers of bars
placed parallelto the sides of the slab and extending
from the edges
aminimumdistance of one-fifth of
theshorterspan.Theareaofreinforcementin each of
thesefour layers shall bethree-quartersof the area
required for
themaximummid-span moment in the
slab.
0-1.9Torsion reinforcement equal
tohalf that
described in
D-t.Sshall be provided atacorner
containedbyedgesover only oneof whichthe slab is
continuous.
D-l.tO
Torsionreinforcementsneed not be provided
at any comer containedby edges over both of which
the slab iscontinuous.
D-1.11Torsion
VI.isgreaterthan2,theslabsshall
bedesignedas spanningone way.
0-2SIMPLYSUPPORTEDSLABS
D-Z.1When simply supported slabs do not have
adequateprovisionto resist torsionat comers and to
preventthecornersfromlifting,the maximum
I
•
I
1E0G
1ST
I
I
I
MIOOLESTRIP
,_.--t:t---Ir Ly -,
ri l"------!'!!'!.~---~-. ~
~T-' ~ .1
l
--Ii ..... MIOOL.ISTRP .+,
L-----.-sToi-----~
-i1~ oJ-Ly-----Jjl-
25AFORSPAN~ 258FORSPAN~
PIO.25DIVISIONOfSLABIN1UMIDl>LEAND EOOESTRIPS
90
IS456:2000
Table26BendingMomentCoefficients forRectangularPanelsSupportedon
FourSideswithProvision for TorsionatCorners
(Clau.fcsD-J.1alit}24.4.1)
Case TypeofPaneland Short Span(~oemcient5 fl. LengSpan
No.MumenlsCOlLctldered (Valuesor1,11.) Coemclenltt
(l,forAll
,..
~
Valuesof
1.0 1.1 1.2 1.3 1.4 1.5 1.75 2.U
'I'.
(I) (2) (3) (4) (~) (6) (7) (8) (9) ClO) (II)
InteriorP(",~/.~:
Negative momentatcontinuousedge O.()320.037O.04JO.()47O.O's10.053 0.060 0.065 0.032
Positive rnornentatnlid-span 0.0240.0280.032(lOJ6O.OJ9 0.0410.0450.049 0.024
2OneSlulrlEtIJ.!eContinuous:
NegativemomentatcontinuousedgeO.OJ7 O.04J (Ul48 O.()~I 0.055 (l.O570.0640.06&0.037
Positive momentatmid-span O.fl280.OJ2·O.(H60.0190.041 0.044 0.0480.052 0.028
]On«Ltm~EtiNtDiscontinuous:
Negative moment at
continuous edge
O.cn70.044 OJl~2 n.OS10.063 Ooll670.0770.085 ()'O~7
Positivemomentatmid-span (),02HO.03J n.()J9()J)440.047 OJ}51 O.O~9 O,()650.028
4TwoAdjllft''''EdgesDiscontinuous:
Negativemomentat continuousedge0.047O.05J(Ul60o.oe..sn.n710.075 0.084 0.091 0.047
Positivemoment.&1null-span O.(n~ 0.040 O.()4~ O.()4<J ().O~J ().O~6 0.063 0.069 ().{n~
~TwoShortEtlJ.:e'.~/Ji.\TO,,,i'UIfIUS:
Nc~ativc moment atcontinuousedgen.045 O,()49 0.052o.n560.0590.0600.0650.069
Positivemoment at mid-span ().(n~ ().()~7 0.0400.0430.0440.045 0.049 (U)~2 O.()J~
(,Two/""IIgHd~('."Discontinuous:
Negative moment atcontinuousedge O,()4~
Positivemomentatmid-span (Un~ O.04J 0,0510.057 0,{.>630.068 0.080 O.08R ().cn~
7 '1'1,,·(,(,1:·tI,t:t',\'[)i,f",mt;NulIlI.\·
(Ollt'l.oll}!Edg« Continuous):
Ncgntivemomentatcontinuousedge 0.057n.064 0.071 O.07lJO.USO 0.084 ().()l)J OJ)'}?
Pn'\ltivcmoment atIl'lid-silan O.04Jn.04S O.O~:l 0.051O.fKlO n.064 0.069 0.073 0.043
XThrc«EII~("'tDi.'t((lIlt;""o,,...
«(Jill'ShorlEdge,'Conunuous):
Negativemomentat eonunuousedge O.()~7
Positive moment at.....d-span ().tl4~ O.O~I ().O~9 (l.(Xl~ 0.071 0.076 0.087 0.096 O.04~
9Fo"I'EdJ.:I·.\'Discontinuous:
Pll\itivl~momentatmid-span ().()~(; 0,064 0.0720.079O.08S 0.089 0.100 0.107 ().O~6
moments per unit width arc given by the following
equation:
Mx=a,~'"I;
.,
My=a
y
,,\./;
where
M.M•~v91.lare same~\Sthose inD-I.l,
\Y •'I
anduandaare momentcoefficients
x y
givenin Table 27
D-2.I.lA;tleast50percentofthetension
reinforcement provided at mid-span should extend
tothesupports. The remaining 50 percent should
extend to within 0.1
IIor 0.1lyof the support. asappropriate.
Table27BendingMoment Coefficients for SlabsSpanningin TwoDirections at
Right Angles, SimplySupportedon FourSides
tClauscD-2.1)
1,/1, 1.0 1.1 I.:! 1.3 1.4 I.~ 1.7~ 2.0 2.5 vo
a O,()62 0.074 ()'()84 O.09J O.()l)9 0.104o.us(l.IIS 0.122 0.124.
(Iv O.(l620.061 O.OSl) ().()~~ o.os: 0.046 n.O]7 0.029 0.020 (lO14
91
Table26BendingMomentCoefficients forRectangularPanelsSupportedon
FourSideswithProvision for TorsionatCorners
(Clau.fcsD-J.1alit}24.4.1)
Case TypeofPaneland Short Span(~oemcient5 fl. LengSpan
No.MumenlsCOlLctldered (Valuesor1,11.) Coemclenltt
(l,forAll
,..
~
Valuesof
1.0 1.1 1.2 1.3 1.4 1.5 1.75 2.U
'I'.
(I) (2) (3) (4) (~) (6) (7) (8) (9) ClO) (II)
InteriorP(",~/.~:
Negative momentatcontinuousedge O.()320.037O.04JO.()47O.O's10.053 0.060 0.065 0.032
Positive rnornentatnlid-span 0.0240.0280.032(lOJ6O.OJ9 0.0410.0450.049 0.024
2OneSlulrlEtIJ.!eContinuous:
NegativemomentatcontinuousedgeO.OJ7 O.04J (Ul48 O.()~I 0.055 (l.O570.0640.06&0.037
Positive momentatmid-span O.fl280.OJ2·O.(H60.0190.041 0.044 0.0480.052 0.028
]On«Ltm~EtiNtDiscontinuous:
Negative moment at
continuous edge
O.cn70.044 OJl~2 n.OS10.063 Ooll670.0770.085 ()'O~7
Positivemomentatmid-span (),02HO.03J n.()J9()J)440.047 OJ}51 O.O~9 O,()650.028
4TwoAdjllft''''EdgesDiscontinuous:
Negativemomentat continuousedge0.047O.05J(Ul60o.oe..sn.n710.075 0.084 0.091 0.047
Positivemoment.&1null-span O.(n~ 0.040 O.()4~ O.()4<J ().O~J ().O~6 0.063 0.069 ().{n~
~TwoShortEtlJ.:e'.~/Ji.\TO,,,i'UIfIUS:
Nc~ativc moment atcontinuousedgen.045 O,()49 0.052o.n560.0590.0600.0650.069
Positivemoment at mid-span ().(n~ ().()~7 0.0400.0430.0440.045 0.049 (U)~2 O.()J~
(,Two/""IIgHd~('."Discontinuous:
Negative moment atcontinuousedge O,()4~
Positivemomentatmid-span (Un~ O.04J 0,0510.057 0,{.>630.068 0.080 O.08R ().cn~
7 '1'1,,·(,(,1:·tI,t:t',\'[)i,f",mt;NulIlI.\·
(Ollt'l.oll}!Edg« Continuous):
Ncgntivemomentatcontinuousedge 0.057n.064 0.071 O.07lJO.USO 0.084 ().()l)J OJ)'}?
Pn'\ltivcmoment atIl'lid-silan O.04Jn.04S O.O~:l 0.051O.fKlO n.064 0.069 0.073 0.043
XThrc«EII~("'tDi.'t((lIlt;""o,,...
«(Jill'ShorlEdge,'Conunuous):
Negativemomentat eonunuousedge O.()~7
Positive moment at.....d-span ().tl4~ O.O~I ().O~9 (l.(Xl~ 0.071 0.076 0.087 0.096 O.04~
9Fo"I'EdJ.:I·.\'Discontinuous:
Pll\itivl~momentatmid-span ().()~(; 0,064 0.0720.079O.08S 0.089 0.100 0.107 ().O~6
moments per unit width arc given by the following
equation:
Mx=a,~'"I;
.,
My=a
y
,,\./;
where
M.M•~v91.lare same~\Sthose inD-I.l,
\Y •'I
anduandaare momentcoefficients
x y
givenin Table 27
D-2.I.lA;tleast50percentofthetension
reinforcement provided at mid-span should extend
tothesupports. The remaining 50 percent should
extend to within 0.1
IIor 0.1lyof the support. asappropriate.
Table27BendingMoment Coefficients for SlabsSpanningin TwoDirections at
Right Angles, SimplySupportedon FourSides
tClauscD-2.1)
1,/1, 1.0 1.1 I.:! 1.3 1.4 I.~ 1.7~ 2.0 2.5 vo
a O,()62 0.074 ()'()84 O.09J O.()l)9 0.104o.us(l.IIS 0.122 0.124.
(Iv O.(l620.061 O.OSl) ().()~~ o.os: 0.046 n.O]7 0.029 0.020 (lO14
91
IS456:1000
ANNEXE
(Clmue25.2)
EFFECTIVELENGTHorCOLUMNS
E.lIntheabsenceofmoreexactanalysis,theeffective
lengthofcolumnsinframedstructuresmaybeobtained
fromtheratioofeffectivelengthtounsupportedlength
'et
l'
giveninFiS.26whenrelativedisplacementofthe
ends of the columnispreventedand inFil.26 when
relative lateral displacement of the ends isDot
prevented.In thelattercase,itisrecommendded-that
theeffectivelengthratio1,,11maynotbetakentobe
lessthan 1.2.
NOTES
1Aprea26and27arereproducedfrom-TheStructural
EnaiDCCJ"No.7,Volume52,July1974bythepenniuioa
oftheCounciloftheIn.titutioDofStructuralEnpaeen,
U.K.
IK
2 InPip.26and27.1l.udIIIaleequaltoIKU
c+ b
wherethelummatioDis tobedoneforthememben
framin.intoajoiatattopandbottomrespectively;andK
c
andK..bein,theflexuralstiffnessforcolumnandbeam
respectively.
E.2 Todeterminewhetheracol\JIDDisI DOswayor
a swaycolumn,stabilityindexQmaybecomputedu
givenbelow:
.where
~D=Bumofaxialloadsonall columninthe
~.
storey,
A.=eluticallycomputedfirstorderlateral
deflection,
H.=totallatera1forceactiDlwithintheitorey,
and
h.=heightofthestorey.
IfQS0.04,thenthecolumnintheframemaybetaken
as noswaycolumn,otherwisethe column will·be
consideredasswaycolumnn.
£.3FornormalusagelSSuminlidealizedconditions.
theeffectivelengthI"of in agivenplanemaybe
assessedon the basisofTable28.
HINGED1·0w-.....,~.........-..-..............-............... ~I
FIXED
D
III
M
;:
FlO.26EFncnvILBNantRATIOSPOIA COLUMNINAPRAMI.wrrHNOSWAY
92
ANNEXE
(Clmue25.2)
EFFECTIVELENGTHorCOLUMNS
E.lIntheabsenceofmoreexactanalysis,theeffective
lengthofcolumnsinframedstructuresmaybeobtained
fromtheratioofeffectivelengthtounsupportedlength
'et
l'
giveninFiS.26whenrelativedisplacementofthe
ends of the columnispreventedand inFil.26 when
relative lateral displacement of the ends isDot
prevented.In thelattercase,itisrecommendded-that
theeffectivelengthratio1,,11maynotbetakentobe
lessthan 1.2.
NOTES
1Aprea26and27arereproducedfrom-TheStructural
EnaiDCCJ"No.7,Volume52,July1974bythepenniuioa
oftheCounciloftheIn.titutioDofStructuralEnpaeen,
U.K.
IK
2 InPip.26and27.1l.udIIIaleequaltoIKU
c+ b
wherethelummatioDis tobedoneforthememben
framin.intoajoiatattopandbottomrespectively;andK
c
andK..bein,theflexuralstiffnessforcolumnandbeam
respectively.
E.2 Todeterminewhetheracol\JIDDisI DOswayor
a swaycolumn,stabilityindexQmaybecomputedu
givenbelow:
.where
~D=Bumofaxialloadsonall columninthe
~.
storey,
A.=eluticallycomputedfirstorderlateral
deflection,
H.=totallatera1forceactiDlwithintheitorey,
and
h.=heightofthestorey.
IfQS0.04,thenthecolumnintheframemaybetaken
as noswaycolumn,otherwisethe column will·be
consideredasswaycolumnn.
£.3FornormalusagelSSuminlidealizedconditions.
theeffectivelengthI"of in agivenplanemaybe
assessedon the basisofTable28.
HINGED1·0w-.....,~.........-..-..............-............... ~I
FIXED
D
III
M
;:
FlO.26EFncnvILBNantRATIOSPOIA COLUMNINAPRAMI.wrrHNOSWAY
92
IS456:2000
HINGED1.0
t
0.7
0.6II:--+--+-~~_~r--~
O.S.......--+--~--+-~
~1
0.3
0.2
0.1
FIXED0 HINGED
00.10.20.30.'0.50.60.70.80.91.0
c ~2 ..
w
)(
u::
Flo.27EFFF.('-IVELENGTHRI\TIOSFORACOLUMN INA
FRAMEWITHOUT RESTRI\INTAGAINSTSWAY
2116BISl07-14
HINGED1.0
t
0.7
0.6II:--+--+-~~_~r--~
O.S.......--+--~--+-~
~1
0.3
0.2
0.1
FIXED0 HINGED
00.10.20.30.'0.50.60.70.80.91.0
c ~2 ..
w
)(
u::
Flo.27EFFF.('-IVELENGTHRI\TIOSFORACOLUMN INA
FRAMEWITHOUT RESTRI\INTAGAINSTSWAY
2116BISl07-14
18W.28Meed ..LeaatbelCom,......Menaben
(C'au#~3)
IS456:2000
Deane01EDd
Ranlnt01Com"..
•lonMemben
(I)
EffectivelyheldIn
positionandrutrained
apinst
rotation
in
bothends
Bft'ectivelyheldin
positionatbothends.
rutrainedapinst
rotationatoneend
(2)
I
I
n.wlleal
VlIIatol......
.....
(3)
0.501
0.701
•.ll._••.•
Valuetl.......
........
(4)
0.651
0.101
Effectivelyheldin
I
UIOI 1.00I
positionatbothends.
butnotrestrained
qainstrotation
Efl'ectivelyheldin
!
1.00I 1.201
positionandrutrained
apinstrotationatone
end.andlittheother
restrainedapinst
rotationbut notheld
lnposition
EfI'cctlvelyheldin
~
1.501
positionlIIldrestrained
apinstrotationin
oneend,andatthe
otherpertlallyrestr·
ainedagainstrotltioo
butnotheldinposition
Effectivelyheldin 2.00I 2.001
positionlitoneend
butnotn:1trained
qainstrotation,lIIld
Ittheotherendratntined
apillStrot8lion
butnothcldinposition
Effectivelyheldin
L
2.00I 2.001
positionlIIIdmtrained
qainst
rotationItone
end
butnotheldin
positionnormtnined
qainstrotationlitthe
othcrend
NOTE
-I
isthelIASlIpported/enathofc:ompmaionmember.
94
(C'au#~3)
IS456:2000
Deane01EDd
Ranlnt01Com"..
•lonMemben
(I)
EffectivelyheldIn
positionandrutrained
apinst
rotation
in
bothends
Bft'ectivelyheldin
positionatbothends.
rutrainedapinst
rotationatoneend
(2)
I
I
n.wlleal
VlIIatol......
.....
(3)
0.501
0.701
•.ll._••.•
Valuetl.......
........
(4)
0.651
0.101
Effectivelyheldin
I
UIOI 1.00I
positionatbothends.
butnotrestrained
qainstrotation
Efl'ectivelyheldin
!
1.00I 1.201
positionandrutrained
apinstrotationatone
end.andlittheother
restrainedapinst
rotationbut notheld
lnposition
EfI'cctlvelyheldin
~
1.501
positionlIIldrestrained
apinstrotationin
oneend,andatthe
otherpertlallyrestr·
ainedagainstrotltioo
butnotheldinposition
Effectivelyheldin 2.00I 2.001
positionlitoneend
butnotn:1trained
qainstrotation,lIIld
Ittheotherendratntined
apillStrot8lion
butnothcldinposition
Effectivelyheldin
L
2.00I 2.001
positionlIIIdmtrained
qainst
rotationItone
end
butnotheldin
positionnormtnined
qainstrotationlitthe
othcrend
NOTE
-I
isthelIASlIpported/enathofc:ompmaionmember.
94
IS456:2000
ANNEXF
(Claus"3.5.3.2and43.1)
CALCULATIONOFCRACKWIDTH
Providedthatthestraininthetensionreinforcement
islimitedto0.8F/E••thedesipsurfacecockwidth.
whichshouldnotexceedtheappropriatevalueJiven
in35.3.2maybecalculated from the following
equation:
Designsurfacecrackwidth
where
a",=distancefromthepointconsideredtothe
surfaceof thenearestlongitudinalbar.
C..=minimumcovertothelonJitudinalbar;
Em=averagesteelstrainatthelevelconsidered.
h=overalldepthof the member.and
x=depthoftheneutralaxis.
Theaveragesteelstrainemmaybecalculatedon the
basisof the
followingassumption:
Theconcreteand the steel
arebothconsideredtobe
fullyelasticin tensionandincompression.Theelastic
modulusofthesteelmaybetakenas200kN/mm
2
and
theelasticmodulusof theconcreteis asderivedfrom
theequationgivenin6.2.3.1bothincompressionand
,intension.
Theseassumptionsareillustratedin Fig.28.
where
h=theoveralldepthofthesection.
'./Ee
x=thedepthfromthecompressionfaceto the
neutralaxis.
I.=themaximumcompressivestress in the
concrete.
t.=thetensilestressin thereinforcement.and
E.=themodulusofelasticityofthereinforcement
Alternatively.as anapproximation.it willnormally
besatisfactorytocalculatethesteelstressonthebasis
ofa
crackedsectionand
thenreducethisbyanamount
equalto thetensileforcegeneratedbythetriangular
distributions.
havingavalueofzeroattheneutralaxis
and a value at the centroid of thetensionsteel ofllol/mm
2
instantaneously.reducingto 0.55N/mm
2
in
the
long-term.actingoverthetensionzonedividedbythesteelarea.Forarectangulartensionzone.thisgives
b(h-x)(a-x)
£m=£1-3E.A.(d-x}
where
A.=areaoftensionreinforcement.
b=widthofthesectionatthecentroidof the
tensionsteel.
£1=strainat the levelconsidered.calculated
ignoringthestiffeningof theconcretein
thetensionzone.
a=distancefromthecampressionfacetothe
pointat
whichthe crackwidthisbeing
calculated.and
d=effectivedepth.
Ie
I
h
•A.•
~""'--ST"88 INCONC'fETE
1N'",,,,ZIN SHORTTERM
O'SSHI'"",2INLONGTERM
SECTIONCRACKED STRAIN STRESS
FIG.28
95
ANNEXF
(Claus"3.5.3.2and43.1)
CALCULATIONOFCRACKWIDTH
Providedthatthestraininthetensionreinforcement
islimitedto0.8F/E••thedesipsurfacecockwidth.
whichshouldnotexceedtheappropriatevalueJiven
in35.3.2maybecalculated from the following
equation:
Designsurfacecrackwidth
where
a",=distancefromthepointconsideredtothe
surfaceof thenearestlongitudinalbar.
C..=minimumcovertothelonJitudinalbar;
Em=averagesteelstrainatthelevelconsidered.
h=overalldepthof the member.and
x=depthoftheneutralaxis.
Theaveragesteelstrainemmaybecalculatedon the
basisof the
followingassumption:
Theconcreteand the steel
arebothconsideredtobe
fullyelasticin tensionandincompression.Theelastic
modulusofthesteelmaybetakenas200kN/mm
2
and
theelasticmodulusof theconcreteis asderivedfrom
theequationgivenin6.2.3.1bothincompressionand
,intension.
Theseassumptionsareillustratedin Fig.28.
where
h=theoveralldepthofthesection.
'./Ee
x=thedepthfromthecompressionfaceto the
neutralaxis.
I.=themaximumcompressivestress in the
concrete.
t.=thetensilestressin thereinforcement.and
E.=themodulusofelasticityofthereinforcement
Alternatively.as anapproximation.it willnormally
besatisfactorytocalculatethesteelstressonthebasis
ofa
crackedsectionand
thenreducethisbyanamount
equalto thetensileforcegeneratedbythetriangular
distributions.
havingavalueofzeroattheneutralaxis
and a value at the centroid of thetensionsteel ofllol/mm
2
instantaneously.reducingto 0.55N/mm
2
in
the
long-term.actingoverthetensionzonedividedbythesteelarea.Forarectangulartensionzone.thisgives
b(h-x)(a-x)
£m=£1-3E.A.(d-x}
where
A.=areaoftensionreinforcement.
b=widthofthesectionatthecentroidof the
tensionsteel.
£1=strainat the levelconsidered.calculated
ignoringthestiffeningof theconcretein
thetensionzone.
a=distancefromthecampressionfacetothe
pointat
whichthe crackwidthisbeing
calculated.and
d=effectivedepth.
Ie
I
h
•A.•
~""'--ST"88 INCONC'fETE
1N'",,,,ZIN SHORTTERM
O'SSHI'"",2INLONGTERM
SECTIONCRACKED STRAIN STRESS
FIG.28
95
IS456:2000
ANNEX·G
(ClGu,,38.1)
MOMENTSOFRESISTA.NCEFORRECTANGULAR AND
T·SECTIONS
G·OThemomentaofrosistanceofrectanlularand
T-Iectionlbaledonthe.I.umptlonaof 38.1areaiven
inthisannex. .
G·lRECTANGULARSECTIONS
G-l.lSectloMWithoutCOmprelllOD
Relntorcement
Themomerrtofresistanceofrectanlularsection.
withoutcompressionreinforcementshouldbeobtained
asfollows:
a)Detenninethedepthofnetutralaxiafromthe
followin,equation:
3•0.87IxAsc
d0.36kkb.d
b) If thevalueofxuldis lessthanthelimiting
value(seeNotebelow38.1), calculate the
moment ofresistance
bythefollowing
expression:
(
Astir)
Mu=0.87fy~ldll-bdfek
c)Ifthe valueofxuldisequalto thelimiting
value.the
momentofresistanceof thesection
is givenbythefollowingexpression:
xu.
max(0 42xu,max)bd2~
Mu tUm=0.36-d-1-.-d- Jek
d) IfXuI dis greaterthan thelimitingvalue.the
sectionshould beredesigned.
In the aboveequations.
.xu=depthofneutralaxis.
d=effectivedepth,
t.=characteristicstrengthof reinforce..
.y
ment,
Alit=area of tensionreinforcement.
t:=characteristiccompressive strength
ofconcrete.
b -widthof thecompressionface.
M - limiting moment of resistance of
u.lin, -
asectionwithoutcompression
reinforcement,and
xu.;iI"~=IimitingvalueofXufrom39.1.
G-l.2SectionwithCompressionReinforcement
Wheremeultimatemoment ofresistanceofsection
exceedstheIlmitllilvalue,M
"
u.compr•••lon
reinforcementmaybeobtainedfromthefollowln,
equation:
whore
M
u
•MyI16m'darelameuinG·I.l,
f.,.desilnstrellincompre.lionreinforce
mentcorrelpondioltoastrainof
(x-d'}
·0.0035u,mu
.xu•mu
where
Xu.JIIIII•thelimitinlvalueofXufrom38.1.
AI&:=areaofcomp'e8Siooreinfcrcement,and
d' ==depthofcompressionreinforcement
fromcompressionface.
The total area of tensionreinforcementshallbe
obtainedfromthefollowingequation:
A.=A.
1+A
1t2
where
A::area of the totaltensile reinforcement•
• l
AM1=area of the tensilereinforcementfor a
singlyreinforcedsection forMg.Um'
and
A..=Af.I0.871."
It. lieIe.: 'I
G-ZFLANGEDSECTION
G-2.1For x
u<
Dr'themomentofresistancemaybe
calculatedfromtheequationgivenin G-l.1•
G·2.2Thelimitingvalueofthemomentofresistance
of thesection maybeobtainedbythefollowing
equationwhentheratioDrIddoes notexceed0.2 :
M=036~(1-0 42Xu,max)I'bd
2
u·d · d Jekw
+0.4Sfek(bf-bw)Df(d-pt)
. where
M oX •dandt.are sameas inG-l.1.
u.u.mtAI c
b=breadthof thecompression face/flange,
I
b=breadthof the web, and
w
D,=thicknessof theflange.
96
ANNEX·G
(ClGu,,38.1)
MOMENTSOFRESISTA.NCEFORRECTANGULAR AND
T·SECTIONS
G·OThemomentaofrosistanceofrectanlularand
T-Iectionlbaledonthe.I.umptlonaof 38.1areaiven
inthisannex. .
G·lRECTANGULARSECTIONS
G-l.lSectloMWithoutCOmprelllOD
Relntorcement
Themomerrtofresistanceofrectanlularsection.
withoutcompressionreinforcementshouldbeobtained
asfollows:
a)Detenninethedepthofnetutralaxiafromthe
followin,equation:
3•0.87IxAsc
d0.36kkb.d
b) If thevalueofxuldis lessthanthelimiting
value(seeNotebelow38.1), calculate the
moment ofresistance
bythefollowing
expression:
(
Astir)
Mu=0.87fy~ldll-bdfek
c)Ifthe valueofxuldisequalto thelimiting
value.the
momentofresistanceof thesection
is givenbythefollowingexpression:
xu.
max(0 42xu,max)bd2~
Mu tUm=0.36-d-1-.-d- Jek
d) IfXuI dis greaterthan thelimitingvalue.the
sectionshould beredesigned.
In the aboveequations.
.xu=depthofneutralaxis.
d=effectivedepth,
t.=characteristicstrengthof reinforce..
.y
ment,
Alit=area of tensionreinforcement.
t:=characteristiccompressive strength
ofconcrete.
b -widthof thecompressionface.
M - limiting moment of resistance of
u.lin, -
asectionwithoutcompression
reinforcement,and
xu.;iI"~=IimitingvalueofXufrom39.1.
G-l.2SectionwithCompressionReinforcement
Wheremeultimatemoment ofresistanceofsection
exceedstheIlmitllilvalue,M
"
u.compr•••lon
reinforcementmaybeobtainedfromthefollowln,
equation:
whore
M
u
•MyI16m'darelameuinG·I.l,
f.,.desilnstrellincompre.lionreinforce
mentcorrelpondioltoastrainof
(x-d'}
·0.0035u,mu
.xu•mu
where
Xu.JIIIII•thelimitinlvalueofXufrom38.1.
AI&:=areaofcomp'e8Siooreinfcrcement,and
d' ==depthofcompressionreinforcement
fromcompressionface.
The total area of tensionreinforcementshallbe
obtainedfromthefollowingequation:
A.=A.
1+A
1t2
where
A::area of the totaltensile reinforcement•
• l
AM1=area of the tensilereinforcementfor a
singlyreinforcedsection forMg.Um'
and
A..=Af.I0.871."
It. lieIe.: 'I
G-ZFLANGEDSECTION
G-2.1For x
u<
Dr'themomentofresistancemaybe
calculatedfromtheequationgivenin G-l.1•
G·2.2Thelimitingvalueofthemomentofresistance
of thesection maybeobtainedbythefollowing
equationwhentheratioDrIddoes notexceed0.2 :
M=036~(1-0 42Xu,max)I'bd
2
u·d · d Jekw
+0.4Sfek(bf-bw)Df(d-pt)
. where
M oX •dandt.are sameas inG-l.1.
u.u.mtAI c
b=breadthof thecompression face/flange,
I
b=breadthof the web, and
w
D,=thicknessof theflange.
96
G-Z.Z.IWhentheratloDr/elexceeds0,2,themoment
ofresi~tllnce ofthesectionmaybecalculatedbythe
followingequation:
Mil=0.36XU.;I'"(1-0.42XU'~lllIJl)/ekb
wd
2
+0.45hk(br-hw)Yr(d-t)
IS456:2000
where)',=(0,JSXu+0.65D,.),but notgreaterthan
D
I
,
and the other
symbolsoreMaineI1Sin0-1.1
nndG·Z.2.
0-Z.3Forx>x>D
J
,
themomentofresistance
.
HI"U~_"
muybecalculatedbytheequation"giveninG-Z.2
whenJ)Ixdoesnotexceed0.43anda·Z.2.1when
f "., • •
n/x
LI
exceeds0.43;InbothcaMe"substitutingX
U
'ma
_
ny
xu'
ofresi~tllnce ofthesectionmaybecalculatedbythe
followingequation:
Mil=0.36XU.;I'"(1-0.42XU'~lllIJl)/ekb
wd
2
+0.45hk(br-hw)Yr(d-t)
IS456:2000
where)',=(0,JSXu+0.65D,.),but notgreaterthan
D
I
,
and the other
symbolsoreMaineI1Sin0-1.1
nndG·Z.2.
0-Z.3Forx>x>D
J
,
themomentofresistance
.
HI"U~_"
muybecalculatedbytheequation"giveninG-Z.2
whenJ)Ixdoesnotexceed0.43anda·Z.2.1when
f "., • •
n/x
LI
exceeds0.43;InbothcaMe"substitutingX
U
'ma
_
ny
xu'
IS456:2000
ANNEXH
(Forrword)
COMMI1TEECOMPOsmON
CementandConcreteSectionalCommittee,CBD2
CItGi,.,.,.
IIIH.C.VIIVISYAlYA
·Cib·,.15dt0ml,
63~.MalleI B.....560003
DRS.C.AHLUWALIA
SHRIG. R.BHARnKAI
SHRIT. N.TIWAItI
DRD.GHOSH (Al~ma,~)
CtUEPBNOIMD!I(OsSIaN)
SUPSRINTENDINOBNOINEI!I(SclS)(Alt~17UI1~)
CHIEPBNGINBER,NAVAOAMDAM
SUPERINTENDINGBNOINIIR(QCC)(Alt,,,",,,)
CHIEFENoINEEI(RBsEAlat-CUM-DlIBCTOl)
RBsEARCHOPFIca(CoNcursTBOINOLOOY)(Al"I'IUJI')
DIRECTOR
JOINTDlRBCTOR (Al'~ntI.I'~)
DlRECI'OR(CMDD)(N&W)
DEPUTYDIRECTOR(CMDD)(NWItS)(Alt.mtlI.)
SHI.K. H.GANOWAL
SHRIV.PA1TA8H1(AllerlUlle)
SHIIV. K.GHANEKAIt
SHRIS.GOPlNA11I
SHillR.TAMILAKAitAN (AII~mtAI.)
SHillS. K.GUHATHAKUITA
SHIIS.~SANKAIlANARAYANAN (Al',,,",'e)
SHit;N. S.BHAL
DRI.SHADMAsooo(A/"mtlt,)
SHRIN. C.JAIN
JOINTDlucroaSTANDARDS(8&5)(CB-I)
JOINTDI~ STANDARDS(8&5)(CB-II)(Alicia,,.,.)
SHiIN. G.JOSHI
SHIll~D.Km.ua(A"~,,",,~)
SHIID. K.KANUNOO
SHI.B.R.MI!&NA(AI"".",.)
SHitIP.KllSHNAMUmtY
SHIIS.CHADAVAmIY (AII,17tIIt,)
ORA. G.MADHAYARAo
SHIIK.MANI(AIt~ruI~)
SHIIJ.SUUP
SHI.PaAJIULl.AKUMAI
SHI'P. P.NAIR(A"~mat~)
B. O.ShiiteA COIIICnIetionTechllOlOl)'Ltd.PuIlC
TheAssociatedCementCompaniesLtd,Mumbai
CentralPublicWork.Department,NewDelhi
SardarS.-ovarNarmanNipmLtd,GandbiDapr
lnilationandPowerROle8R:hInstitute.Amritaar
A.P.BnsineeringRcaearchLaboI'llOriel,Hyderabad
CentralWaterCommission,NewDelhi
HyderabadIndustriesLtd.Hyderabad
StnlcturalEnaiDeeringResearchCentre(CSIR).Ohaziabad
TheIndiaCementaLtd,Chenaai
GaaaoDDunkerley...CoLtd.Mumbai
CeatralSuUdi..,Raeardllnltiture(CSIR).Roorbe
CementCorporationofIndia.NewDelhi
Researth.Deai....clStaDdIrdIOrpnlzIdoa(MinistryofRailway),
Luckaow
IDdianHumePipesCoLtd.Mumbai
NatiODllTellHouse,Calcuaa
LInenandToubroLimited.Mumbai
StructlIraiEnlineerinlResearchCcnn(CSIR),Chenaaa
HOIpilalservicesCODl~ C;orporation(lacIia)Ltd,
NewDelhi
MinistryofSurfaceTnmspod,Depuunentof Surf..Tranapolt
(RoadsWiD,),NewDelhi
(CUllliauetJtillflGI'99)
ANNEXH
(Forrword)
COMMI1TEECOMPOsmON
CementandConcreteSectionalCommittee,CBD2
CItGi,.,.,.
IIIH.C.VIIVISYAlYA
·Cib·,.15dt0ml,
63~.MalleI B.....560003
DRS.C.AHLUWALIA
SHRIG. R.BHARnKAI
SHRIT. N.TIWAItI
DRD.GHOSH (Al~ma,~)
CtUEPBNOIMD!I(OsSIaN)
SUPSRINTENDINOBNOINEI!I(SclS)(Alt~17UI1~)
CHIEPBNGINBER,NAVAOAMDAM
SUPERINTENDINGBNOINIIR(QCC)(Alt,,,",,,)
CHIEFENoINEEI(RBsEAlat-CUM-DlIBCTOl)
RBsEARCHOPFIca(CoNcursTBOINOLOOY)(Al"I'IUJI')
DIRECTOR
JOINTDlRBCTOR (Al'~ntI.I'~)
DlRECI'OR(CMDD)(N&W)
DEPUTYDIRECTOR(CMDD)(NWItS)(Alt.mtlI.)
SHI.K. H.GANOWAL
SHRIV.PA1TA8H1(AllerlUlle)
SHIIV. K.GHANEKAIt
SHRIS.GOPlNA11I
SHillR.TAMILAKAitAN (AII~mtAI.)
SHillS. K.GUHATHAKUITA
SHIIS.~SANKAIlANARAYANAN (Al',,,",'e)
SHit;N. S.BHAL
DRI.SHADMAsooo(A/"mtlt,)
SHRIN. C.JAIN
JOINTDlucroaSTANDARDS(8&5)(CB-I)
JOINTDI~ STANDARDS(8&5)(CB-II)(Alicia,,.,.)
SHiIN. G.JOSHI
SHIll~D.Km.ua(A"~,,",,~)
SHIID. K.KANUNOO
SHI.B.R.MI!&NA(AI"".",.)
SHitIP.KllSHNAMUmtY
SHIIS.CHADAVAmIY (AII,17tIIt,)
ORA. G.MADHAYARAo
SHIIK.MANI(AIt~ruI~)
SHIIJ.SUUP
SHI.PaAJIULl.AKUMAI
SHI'P. P.NAIR(A"~mat~)
B. O.ShiiteA COIIICnIetionTechllOlOl)'Ltd.PuIlC
TheAssociatedCementCompaniesLtd,Mumbai
CentralPublicWork.Department,NewDelhi
SardarS.-ovarNarmanNipmLtd,GandbiDapr
lnilationandPowerROle8R:hInstitute.Amritaar
A.P.BnsineeringRcaearchLaboI'llOriel,Hyderabad
CentralWaterCommission,NewDelhi
HyderabadIndustriesLtd.Hyderabad
StnlcturalEnaiDeeringResearchCentre(CSIR).Ohaziabad
TheIndiaCementaLtd,Chenaai
GaaaoDDunkerley...CoLtd.Mumbai
CeatralSuUdi..,Raeardllnltiture(CSIR).Roorbe
CementCorporationofIndia.NewDelhi
Researth.Deai....clStaDdIrdIOrpnlzIdoa(MinistryofRailway),
Luckaow
IDdianHumePipesCoLtd.Mumbai
NatiODllTellHouse,Calcuaa
LInenandToubroLimited.Mumbai
StructlIraiEnlineerinlResearchCcnn(CSIR),Chenaaa
HOIpilalservicesCODl~ C;orporation(lacIia)Ltd,
NewDelhi
MinistryofSurfaceTnmspod,Depuunentof Surf..Tranapolt
(RoadsWiD,),NewDelhi
(CUllliauetJtillflGI'99)
(CtRitillll,d/tTl".pal'98)
M,mbcrJ
MDt.SBClBTAIV
DIIICIOI(OVIL)(Alt,""",)
SRIS.K.NATHANI.SO I
DRA.S.00IL,BB(Alt'l7Itlt,)
SKIIS.S.SBlHIA
SMa.SATANDIIKUMAR(Alt,mat,)
SHIIY.R.PHuu. .
SMRIA.K.SHAlMA(AI""",,,)
DaC.RAJICUNAl
DRK.MOHAN(Alr,na",,)
SHI'O.RAMDAS
8HRIR.C.SHARMA(AII,mal,)
SMRIS.A.RIDDI
SHIIJ. S.SANOANCRIA
SMR.L. N.AOARWAL(A.lt,nul',)
SH1.VBNKATACH~
SHIIN.CHANDRASBICAIAN(Alt,rnat,)
Su....NTIINDINOENOINIBR(DISION)
ExBCUnVIENOINEER(S.M.R.DlVlSION)(Alltrn"te)
SHR.A.K.CHADHA
SHRIJ.R.SIL,Alt,na"t,)
DRH.C.VISYBSVARAYA
SHI.D.C.CHATURVBDI(All,nun,)
SHIllVINOD KUMAI
Director(CivEn,.)
IS456:ZOOO
R,p"J,ntlllll
CentralBoardofIrriptionandPower,NewDelhi
Engineer·in-ehief'lBranch,ArmyHeadquarters,NewDelhi
CentralRoadResearchInstitute(CSIR),NewDeihl
IndianRoadsConll'ell, NewDelhi
NationalCouncilforCementandSuildin.Materials,NewDelhi
Directorate0eneraIofSuppliesandDisposal.,NewDelhi
OammoDlDdiaLtd,Mwnbal
Geololica1SurveyofIndia,CaI~utta
CentralSoilandMaterial.Reaeard\Station,NewDelhi
PublicWorksDepartment,GovernmentofTamilNadu.Chennai
HindustanPrefabLtd. NewDelhi
TheInstitutionofEngineers(India),Calcutta
DirectorGeneral.8IS(Ex·ldficioM,mber)
M,mber-S,crtlar;e.f
SHRIJ.K.PRASAD
AddlDirector(Civ Engg).DIS
SHRISANJAYPANT
DeputyDirector(CivEngl),DIS
PanelforRevisionofDesignCodes
CllftV',..'
DRC.RAlKUMAIt.
M,,,,.,,
SHIIV. K.GHAN8KAJl
SHa.S. A.RIDDI
SHa,JOSBKURIAN
DRA. K.MITrAL
DRS.C.MAm
DRAND..KUMAR(Alternatt)
PRopA.K.JAIN
DRV.THllUVINODAM
99
NationalCouncilfor(:ementand Buildin.Materials,BallabBarb
StructuralEngincerinaResearchCentre,Ghaziabad
GammonIndiaLtd.Mumbai
CentralPublicWorksDepartment,NewDelhi
CentralPublicWorksDepartment.New Delhi
NationalCouncilforCementandBuildingMaterials.Ballabgarh
UniversityofRoorkee,Roorkee
SchoolofPlanningandArchitecture,NewDelhi
(Cllntinuedonpage1(0)
M,mbcrJ
MDt.SBClBTAIV
DIIICIOI(OVIL)(Alt,""",)
SRIS.K.NATHANI.SO I
DRA.S.00IL,BB(Alt'l7Itlt,)
SKIIS.S.SBlHIA
SMa.SATANDIIKUMAR(Alt,mat,)
SHIIY.R.PHuu. .
SMRIA.K.SHAlMA(AI""",,,)
DaC.RAJICUNAl
DRK.MOHAN(Alr,na",,)
SHI'O.RAMDAS
8HRIR.C.SHARMA(AII,mal,)
SMRIS.A.RIDDI
SHIIJ. S.SANOANCRIA
SMR.L. N.AOARWAL(A.lt,nul',)
SH1.VBNKATACH~
SHIIN.CHANDRASBICAIAN(Alt,rnat,)
Su....NTIINDINOENOINIBR(DISION)
ExBCUnVIENOINEER(S.M.R.DlVlSION)(Alltrn"te)
SHR.A.K.CHADHA
SHRIJ.R.SIL,Alt,na"t,)
DRH.C.VISYBSVARAYA
SHI.D.C.CHATURVBDI(All,nun,)
SHIllVINOD KUMAI
Director(CivEn,.)
IS456:ZOOO
R,p"J,ntlllll
CentralBoardofIrriptionandPower,NewDelhi
Engineer·in-ehief'lBranch,ArmyHeadquarters,NewDelhi
CentralRoadResearchInstitute(CSIR),NewDeihl
IndianRoadsConll'ell, NewDelhi
NationalCouncilforCementandSuildin.Materials,NewDelhi
Directorate0eneraIofSuppliesandDisposal.,NewDelhi
OammoDlDdiaLtd,Mwnbal
Geololica1SurveyofIndia,CaI~utta
CentralSoilandMaterial.Reaeard\Station,NewDelhi
PublicWorksDepartment,GovernmentofTamilNadu.Chennai
HindustanPrefabLtd. NewDelhi
TheInstitutionofEngineers(India),Calcutta
DirectorGeneral.8IS(Ex·ldficioM,mber)
M,mber-S,crtlar;e.f
SHRIJ.K.PRASAD
AddlDirector(Civ Engg).DIS
SHRISANJAYPANT
DeputyDirector(CivEngl),DIS
PanelforRevisionofDesignCodes
CllftV',..'
DRC.RAlKUMAIt.
M,,,,.,,
SHIIV. K.GHAN8KAJl
SHa.S. A.RIDDI
SHa,JOSBKURIAN
DRA. K.MITrAL
DRS.C.MAm
DRAND..KUMAR(Alternatt)
PRopA.K.JAIN
DRV.THllUVINODAM
99
NationalCouncilfor(:ementand Buildin.Materials,BallabBarb
StructuralEngincerinaResearchCentre,Ghaziabad
GammonIndiaLtd.Mumbai
CentralPublicWorksDepartment,NewDelhi
CentralPublicWorksDepartment.New Delhi
NationalCouncilforCementandBuildingMaterials.Ballabgarh
UniversityofRoorkee,Roorkee
SchoolofPlanningandArchitecture,NewDelhi
(Cllntinuedonpage1(0)
IS456:2000
tContlnuedfromPdf.:~99)
Mtmbtr.f
StnuS.A. Rr;;ODI
DRC.RAJKUMAR
MGIPRRND-2116815/2OO7-10,OOO.
SpecialAd-HocGroupforRevisionof IS456
Ctwvtntr
DRH.C.VI5VBSVARYA
'Chandrikn'ot I~th Cro14~,
63·64,Mnlleswnnun,Bonplore560OO~
Rtpre,felltltlN
GammonIndioLtd,Muulbai
NnrinnQlCouncilforCementandBuildingMnterinlR,Rollnhgnrh
100
tContlnuedfromPdf.:~99)
Mtmbtr.f
StnuS.A. Rr;;ODI
DRC.RAJKUMAR
MGIPRRND-2116815/2OO7-10,OOO.
SpecialAd-HocGroupforRevisionof IS456
Ctwvtntr
DRH.C.VI5VBSVARYA
'Chandrikn'ot I~th Cro14~,
63·64,Mnlleswnnun,Bonplore560OO~
Rtpre,felltltlN
GammonIndioLtd,Muulbai
NnrinnQlCouncilforCementandBuildingMnterinlR,Rollnhgnrh
100
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