Building construction materials -Steel

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1. Building Construction Materials
Steel
Mr. K. R. Patil
Assistant Professor
Department of Civil Engineering
D. Y. Patil College of Engineering &
Technology, Kolhapur

2. Steel
•Steelisthemostsuitablebuildingmaterialamongmetallicmaterials.
•Thisisduetoawiderangeandcombinationofphysicaland
mechanicalpropertiesofsteel.
•Bysuitablycontrollingthecarboncontentandheattreatment,adesired
combinationofhardness,ductilityandstrengthcanbeobtainedinsteel.
•Propertiesandusesofvarioustypesofsteel
1.Mildsteel
•Mildsteelisalsoknownaslowcarbonorsoftsteel.
•Itisductile,malleable,tougherandelastic.
•Itrustsquickly.
•Carboncontent–0.15–0.3%
•Ultimatetensilestrength–600-800N/mm2
•Mildsteelisusedintheformofrolledsections,reinforcingbars,roof
coverings,sheetpilesandinrailwaytracks.

3. 2.Highcarbonsteel
•Itisalsoknownashardsteel.Itistougherandmoreelasticthanmild
steel.
•Carboncontent–0.6–0.8%
•Ultimatetensilestrength–1400-2000N/mm
2
•Highcarbonsteelisusedforreinforcingcementconcreteand
prestressedconcretemembers.Itisalsousedformakingtoolsand
machineparts.
3.Hightensilesteel
•Itisamediumcarbonsteel.Itisalsoknownashighstrengthsteel.
•Carboncontent–0.55–1.5%
•Ultimatetensilestrength–2000N/mm2
•Minimumelongation–10%
•Hightensilesteelisusedinprestressedconcreteconstruction.

4. •Rolled Steel Sections
•Structuralsteelcanberolledintovariousshapesandsizesinrolling
mills.I.S.HandBookNo.1publishedbyBureauofIndianStandards
providesthedimensions,weightsandgeometricalpropertiesof
varioussections.
Rolled steel I-sections ( Fig. a)
Rolled steel channel sections ( Fig. b)
Rolled steel T-sections ( Fig. c)
Rolled steel angle-sections ( Fig. d)
Rolled steel tube-sections ( Fig. e)
Rolled steel bars ( Fig. f)
Rolled steel flats ( Fig. g)
Rolled steel plates
Rolled steel sheets

5. 1.AnI-sectionisdesignatedbyitsdepthandweight.
•e.g.ISLB(IndianStandardLightWeightBeams)[email protected]
N/mmeans,theI-sectionis500mmdeepanditsselfweightis
735.7Npermetrelength.
•Achannel-sectionisdesignatedbyitsdepthandweight.
•e.g.ISLC(IndianStandardLightWeightChannels)[email protected]
N/mmeansthatthechannelsectionis350mmdeepandtheself
weightis380.6Npermetrelength.
•AT-sectionisdesignatedbyitsdepthandweight.
•[email protected]/mmeansthattheTeesectionis125mm
deepandtheselfweightis268.8Npermetrelength.
•Anangle-sectionisdesignatedbyitsleglengthandthickness.
•e.g.ISA40x25x6mmmeans,thesectionisunequalanglewith
legs40mmand25mminlengthandthicknessoflegs6mm.

6. •Steeltubesaredesignatedbytheiroutsidediameterandselfweight.
•Steelflatsaredesignatedbywidthandthicknessofthesection.
•e.g.30ISF10mmmeanstheflatis30mmwideand10mmthick.
•Steelplatesaredesignatedbylength,widthandthicknessofthe
section.
•e.g.ISPL2000mmx1000mmx8mmmeanstheplateis2000mm
long,1000mmwideand8mmthick.
•Steelsheetsaredesignatedbylength,widthandthicknessofthe
section.
•e.g.ISSH2000mmx600mmx4mmmeansthesheetis2000mm
long,600mmwideand4mmthick.
•Roundbarsaregenerallyusedasreinforcementinreinforcedconcrete
structures.
•Roundbarsandsquarebarsarealsousedfordecorativepurposesand
grillsforwindows,fencing,parapets,etc.

7. •Reinforcingsteelbars
•Cementconcreteismostcommonlyusedconstructionmaterialthroughoutthe
world.
•Concreteisverygoodincompressionbutisextremelyweakintension.
•Toovercomethisweakness,steelreinforcementisrequired.Steel
reinforcementisavailableintheformofbarsofspecificdiameterswith
differentchemicalcompositionlikemildsteelandhightensilestrength.
•Typesandgradesofreinforcingbars
•Highyieldstrengthdeformed(HYSD)bars
•Thesebarshaveribsordeformationsonthesurface,whichpreventlongitudinal
movementofthebarrelativetothesurroundingconcrete.
•Thus,thedeformedsurfaceensuresbetterbondbetweenreinforcementand
concrete.HYSDbarsresultinaconsiderableincreaseinyield,tensileandbond
strengthwhentwistedhotorcold.
•Coldtwisteddeformed(CTD)barsaremostsuitableforconstructionpurpose
andarewidelyusedinIndia.CTDbarswithtrademarkTORarecalledTor-
steel.
•Torsteelishighstrengthdeformedbarswithhighyieldandbondstrength.CTD
barsareavailableinFe-415grade.

8. •Thermo-mechanicallytreated(TMT)bars
•Theseareextrahighstrengthbars,whicheliminatecoldtwisting.In
thisprocess,thesteelbarsreceiveashortintensivecoolingastheypass
throughawatercoolingsystemafterthelastrollingmillstand.The
reductionintemperatureconvertsthesurfacelayerintoahardened
structure.
•TMTbarscanbeusedforgeneralconcretereinforcementinbuildings,
bridgesandvariousotherconcretestructures.Theyarehighly
recommendedforuseinhigh-risebuildingsbecauseofsavinginsteel
duetothehigherstrength.
•TMTbarsareavailableinTMT415,TMT500andTMT550types.
HerethenumberindicatesminimumyieldstrengthinN/mm2.
•Thelatestdevelopmentinreinforcingbarsisthermo-mechanically
treatedhigh-strengthcorrosionresistant(TMT-HCR)bars.Thesebars
havesuperiorresistancetoaggressiveweatherconditions.TMT-HCR
barsarewidelyusedincoastalandmarineenvironmentswhichare
susceptibletoocorrosion,bridges,dams,industrialstructures,highrise
buildingsandundergroundstructures.

9. •Uses of Steel:
•Structuralmaterialintrusses,stanchions,beamintheformofvarious
sections.
•Nonstructuralcomponentsforgrills,stairs,windows&doors.
•Infabricationofsteelpipes,tubes,tanks,ductsetc.
•Usedascorrugatedsheetswhichactasroofoverthestructures.
•MildsteelisusedasdistributionsteelinR.C.C.members.
•TorsteelisusedasmainsteelinR.C.C.members.
•Hightensilesteelcablesareusedinprestressedconcretegirders.