Moment Resisting Frame.pdf

A full explanation for the lateral resisting system: CONCRETE MOMENT RESISTING FRAME-STEEL MOMENT RESISTING FRAME- COMPOSITE MOMENT RESISTING FRAME

1. LATERAL RESISTING STRUCTURAL
SYSTEM:
MOMENT RESISTING FRAME
1
Presented By
Eng. ZEINAB AWADA
Email
[email protected]
MASTER OF CIVIL ENGINEERING -LEBANON
ADVANCED STRUCTURAL SYSTEMS COURSE
Mon, Nov 29-2021

2. OUTLINE
2
❑INTRODUCTION
❑CONCRETEMOMENTRESISTINGFRAME
❑STEELMOMENTRESISTINGFRAME
❑COMPOSITEMOMENTRESISTINGFRAME

3. 3
•Theseismicanalysisanddesignhastraditionallyfocusedonreducing
theriskoflossoflife.
•Buildingcodeshavedevelopedprovisionsaroundlifesafetyconcerns,
i.e.,topreventcollapseunderthemostintenseearthquakeexpectedat
asiteduringitslife.
•Thesuccessfulperformanceofbuildingsinareasofhighseismicity
dependsonacombinationofstrength,ductilitymanifestedinthe
detailsofconstruction,andthepresenceofafullyinterconnected,
balanced,andcompletelateral-force-resistingsystem.
•Verybrittlelateral-force-resistingsystemscanbeexcellentperformers
aslongastheyareneverpushedbeyondtheirelasticstrength.
INTRODUCTION
❖General Requirements

4. ❖What is a Moment Resisting Frame!
INTRODUCTION
•Usedinsteelandreinforcedconcretebuildings
•Thissystemconsistsofbeams,columnsandrigidjoints
•Capableofresistingbothverticalandlateralloadsbythebending
ofbeamsandcolumns
•Beam-columnconnectionshaveadequaterigiditytoholdthe
originalanglesbetweenintersectingmembersunchanged
•Reinforcedconcreteisanidealmaterialforthissystembyvirtueof
itsnaturallymonolithicbehavior
•Forsteelbuildings,rigidframingisachievedbyreinforcingbeam-
columnconnections
4

5. 5
❖Disadvantages of Moment Resisting Frame!
1.Greaterdeflectionanddriftcomparedtothatofbracedframesorshearwalls
2.localizedstressconcentrationsatrigidjoints
3.Requirescareintheerectionofconnectionsinordertoresistlateralloads
properly
4.Expensivemomentconnections
5.Ahighlyrigidityintheupperfloors,wherethereisalittledeformationmorethan
thelowerfloors
1.Providesflexibilityforarchitecturaldesignandlayout
2.Sufficientstiffnesstoresistwindandearthquakeinducedlateralloadsinbuildings
ofuptoabout25stories
❖Advantages of Moment Resisting Frame!
CHARACTERISTICS OF MRF

6. 6
CONCRETE MOMENT FRAME
DESIGN REQUIREMENTS AND ASSUMPTIONS
PART 1

7. 7
❖Types of Moment Resisting Frame!
•Anordinaryreinforcedconcretemomentispermitted
tobeusedinbuildingsassignedtoSDCB
•StructuresassignedtoSDCCarepermittedtoutilize
intermediateconcretemomentresistingframes
•Specialreinforcedconcretemomentframesare
requiredinstructuresassignedtoSDCD,EandF
ACI318-19CHAPTER18
✓Ordinarymomentframesshallsatisfy18.3
✓Intermediatemomentframesshallsatisfy
18.4
✓specialmomentframesshallsatisfy18.2.3
through18.2.8and18.6through18.8
1.Ordinarymomentframes
2.Intermediatemomentframes
3.specialmomentframes
CHARACTERISTICS OF MRF

8. 8
Therearetwocausesoflateraldrift:
1.Duetocantileverbendingofthebuilding
(bendingdeformation),whichis
approximately20percentofthetotallateral
drift
2.Duetobendingofthebeamsandcolumns
(sheardeformation),approximately65per
centisduetothebendingofthebeams,and
15percenttothecolumns,totaling
approximately80percentofthetotallateral
drift
❖Drifts in Moment Resisting Frame
CHARACTERISTICS OF MRF

9. 9
•Capacityofbuildingmaterials,systems,or
structurestoabsorbenergybydeformingintothe
inelasticrange
•Thecapabilityofastructuretoabsorbenergy,with
acceptabledeformationsandwithoutfailure,isa
verydesirablecharacteristicinanyearthquake-
resistantdesign
•Concrete,abrittlematerial,mustbeproperly
reinforcedwithsteeltoprovidetheductility
necessarytoresistseismicforces
CHARACTERISTICS OF MRF
❖Definition of Ductility

10. 10
•dissipateenergythroughtheirductilityandmay
undergoexcessivelateraldeformations.
•ductilityisachievedbytheformationofplastichingesin
thecolumnsandbeams.
•whentheyaredeformedbeyondtheirelasticlimits,a
largepartoftheenergyisdissipatedbytheplastic
hinges.
•ductilityofreinforcedconcretedependsonthedesign.
•Inreinforcedconcreterigidframes,itisnecessaryto
designthecolumnstobestrongerthanthebeamsso
thatplastichingescanbeformedinthebeams.
CHARACTERISTICS OF MRF
❖Ductility in Rigid Frames

11. 11
•Theformationofplastichingesatthebeam-columninterface
resultsinlargeinelasticstraindemandsattheconnectionleading
tobrittlefailure.
•theprequalifiedconnectionsaredesignedtoproducetheplastic
hingeswithinthebeamspan.
•theformationofplastichingeswithinthebeamspaniscapableof
dissipatinglargeamountsofenergy,withoutfailure.
•Thisconditionmaybeachievedbyreducingthesectionofthe
beamatthedesiredlocationoftheplastichingeorbyreinforcing
thebeamattheconnectiontopreventtheformationofahingein
thisregion.
❖Strong Column–weak Beam
CHARACTERISTICS OF MRF

12. 12
•frameswithcolumnsthatareweakerinflexurethanthe
framingbeamscanformweak-storymechanisms,inwhich
plastichingesformatthebaseandtopofallcolumnsina
story.
•largeinelasticdisplacementsproducedinthecolumnsincrease
theP-deltaeffectandmayleadtocolumnfailure.
•Thestrongcolumn–weakbeamconceptmaybeachievedin
accordancewiththerequirement:
1.Byassuringthat,ateachbeam–columnjoint,theflexural
resistanceofcolumnsissubstantially(20%)morethan
theflexuralstrengthofbeams.
❖Strong Column–Weak Beam
CHARACTERISTICS OF MRF

13. 13
•Whenaxialloadisimposedonthedeflectedshapeofthe
frame,additionalswayoccursintheframe.
•Thisadditionaldeflectionimposessecondarymomentsin
thecolumn.
•Atanypoint,thetotalmomentMcanbeconsideredasa
combinationofthemomentM0duetoendmomentsplus
theadditionofthemomentcausedbyPactingatan
eccentricityy.
•Thus,M=M0+P∆
❖P∆-Effect
CHARACTERISTICS OF MRF

14. 14
•ThefactorRinthedenominatorofbaseshearequationsisanempiricalresponsereductionfactor
intendedtoaccountforboththedampingandductility.
•AhighervalueofRhastheeffectofreducingthedesignbaseshear.
•forRCspecialmoment-resistingframe,thefactorhasavalueof8,whereasforordinarymoment-resisting
frame,thevalueis3.
❖Structural System Coefficient R
CHARACTERISTICS OF MRF
•Thisreflectsthefactthataspecial
moment-resistingframeperformsbetter
duringanearthquake.

15. 15
ORDINARY CONCRETE MOMENT FRAMES (OMF) SDC B
❖General Requirements: Frame Beams
•Theflexuralreinforcementatbothtopandbottom
facesofthesectionmustincludeatleasttwo
continuousbarsalongthespan.
•TheareaoftheContinuousbottombarsinthe
section,shallhaveanareanotlessthan25%ofthe
maximumareaofbottombarsalongthespan.
•Thesebars(flexuralRFT.)shallbeanchoredtodevelop
fyintensionatthefaceofsupport.
•Theserequirementsforstructuresnotexpectedtobe
subjectedtostronggroundmotion.

16. 16
•flexuralreinforcement:
1.similartoordinarymomentbeams.
2.Thelimitsofgrossreinforcementratio:
•Shearreinforcement:
a.minimumtiesarerequiredintherectangularsections:
1.Minimumdiameteroftiesis10mm(#3).
2.Maximumspacingoftiesisgivenas:
✓b=Dimensionoftheshortersideofthemember.
✓db=Diameterofthemainreinforcementbars.
✓dt=Diameterofthetiebars.
ORDINARY CONCRETE MOMENT FRAMES (OMF) SDC B
❖General Requirements: Frame Columns
•Thespacingofspirals:
1.smax=80mm(3in)
2.smin=25mm(1in)
Ratio of the volume of spirals to the
volume of concrete

17. 17
❖Flexural Reinforcement: Frame Beams
•Positivemomentstrengthatjointface≥one-
thirdnegativemomentstrengthprovidedat
thatfaceofthejoint.
•Neitherthenegativenorthepositive
momentstrengthatanysectionalongthe
memberlengthshallbelessthanone-fifth
themaximummomentstrengthprovidedat
thefaceofeitherjoint.
•Thetopreinforcementisusuallysplicednear
midspanandthebottomreinforcementis
splicednearthesupport.
INTERMEDIATE CONCRETE MOMENT FRAMES (IMRF) SDC C

18. 18
❖Transverse Reinforcement: Frame Beams
•Thefirststirrupshallbelocatednomorethan2inor
50mm,fromthefaceofthesupportingmember.
•Maximumstirrupspacingshallnotexceed
•d/4.
•8×diameterofsmallestlongitudinalbar
•24×diameterofstirrupbar
•12in.or300mm
•Stirrupsshallbespacedatnomorethand/2
throughoutthelengthofthemember
INTERMEDIATE CONCRETE MOMENT FRAMES (IMRF) SDC C
•Thepotentialplastichingeregionisassumedtoextendadistance(2h)fromthefaceofthesupport.
•Stirrupsshallbeprovidedatbothendsofamemberoveralengthequalto2hfromthefaceofthesupporting
membertowardmid-span.

19. 19
❖Transverse Reinforcement: Frame columns
•L0isassumedlengthoftheanticipatedplastichingeregion
•ThelengthL0shallnotbelessthanthelargestof
•Clearspan/6.
•Maximumcross-sectionaldimensionofmember.
•18in.
•MaximumtiespacingshallnotexceedS0overalengthL0
measuredfromeachjointface.
•SpacingS0shallnotexceedthesmallestof:
INTERMEDIATE CONCRETE MOMENT FRAMES (IMRF) SDC C
•ThefirsttieshallbelocatednofartherthanS0/2fromthejointface.
•TiespacingoutsideofthelengthLoshallnotexceed2S0.

20. 20
❖General Requirements: JOINT
INTERMEDIATE CONCRETE MOMENT FRAMES (IMRF) SDC C
•Beamlongitudinalreinforcementmustextendtothe
farofthejointcoreandmustbedevelopedin
tension.

21. 21
❖Dimension limit: Frame Beams
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
•Thewebwidthshallnotbelessthan0.3
timesitsheightand250mm,
•Thewebwidthshallbegreaterthan3C2and
C2+1.5C1
•Projectionofthebeamwidthbeyondthe
widthofthesupportingcolumnoneachside
shallnotexceedthelesserofc2and0.75c1.
•Theclearspanofthebeamshallnotbeless
thanfourtimesitseffectivedepth.

22. 22
❖Flexural Reinforcement: Frame Beams
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
•Thepositivemomentatthefaceofthe
columnmustexceedonehalfthenegative
momentstrengthprovidedatthefaceofthe
supportingcolumn.
•Theminimumpositiveandnegative
momentsatmid-spanmustexceedone
fourththemaximummomentstrength
providedatthefaceofthesupporting
column.
•Atleasttwobarsatthetopandbottom
facesofthebeammustbecontinuous.

23. 23
❖Flexural Reinforcement: Frame Beams
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
•Therequireddevelopmentlengthforstraightbarsare
multiplesofthehookedbardevelopmentlengthsinACI
18.8.5.1:
•Minimumdevelopmentlength2.5Ldhforbottombars
•Minimumdevelopmentlength3.25Ldhfortopbars

24. 24
❖Flexural Reinforcement: Frame Beams
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
•Therequirementsforlapsplicesinbeamsof
specialmomentframesaregiveninACI
18.6.3.3:
1.Hooporspiralreinforcementspacedon
centernomorethanthelesserofd/4
and4in.Mustbeprovidedoverthelap
splicelength.
2.Thesplicelocationshallnotbelessthan
2hfromthefaceofthesupportorfrom
thecriticalsectionofanyplastichinge.
3.Lapsplicesmustnotbelocatedwithin
joints

25. 25
❖Transversal Reinforcement: Frame Beams
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
•Thecalculatedhoopspacing,s,within2hmustbe
lessthanorequaltothesmallestofthefollowing:
•Thecentertocenterspacingofthetransversely
supportedlongitudinalbarsinbeamsmustbeless
thanorequalto14in

26. 26
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
❖Dimension Limit: Frame Columns
•Shortestcross-sectionaldimension
measuredonastraightlinepassingthrough
thegeometriccentroid≥12in.
•Ratiooftheshortestcross-sectional
dimensiontotheperpendiculardimension
≥0.4.

27. 27
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
•Thesplicelocationshallbelimitedtothecenterhalfof
thebeamcolumntokeepthespliceoutsideofthe
regionsoftheplastichinges.
•theclearheightofthecolumnisgreaterthanorequal
to2.5timesthetensiondevelopmentlengthofthe
bars.
•Atleastsixlongitudinalbarsarerequiredincolumns
•Thepotentialplastichingeregionisassumedtobe
withinadistance(Lo)fromthefaceofthesupport.
•Theminimumlengthofplastichingeregion(Lo)is
givenasafunctionoftheclearspanofthecolumn,the
dimensionsofthesectionand500mm(18in).
❖Flexural Reinforcement: Frame Columns

28. 28
•Theamountandspacingofhoopsintheplastichingeregion
mustextendthroughthejointasshowninfigure.
•Thespacingofhoopsinthemiddleofthebeamshallneither
exceed6dbnor150mm(6in)and5db.
SPECIAL CONCRETE MOMENT FRAMES (SMRF) SDC D-E-F
❖Transversal Reinforcement: Frame Columns

29. 29
STEEL MOMENT FRAME DESIGN REQUIREMENTS
AND ASSUMPTIONS
PART 2

30. 30
•steelmomentframeshavebeeninuseformorethanonehundredyears.
•Itwasbelievedthat:
1.Weldedsteelmoment-framebuildingsasbeingamongthemost
ductilesystemscontainedinthebuildingcode.
2.Thesteelmoment-framebuildingswereessentiallyinvulnerableto
earthquake-inducedstructuraldamageandthoughtthatshouldsuch
damageoccur,itwouldbelimitedtoductileyieldingofmembers
andconnections.
3.thetypicalconnectionemployedinsteelmoment-frame
construction,wascapableofdevelopinglargeplasticrotations,
withoutsignificantstrengthdegradation.
•Followingthe1994Northridgeearthquake,engineersweresurprisedto
discoverthatmorethan20modernspecialsteelmomentframestructures
hadexperiencedbrittlefracturingoftheirweldedbeam-to-column
connections.
HISTORY OF SPECIAL MOMENT FRAME DEVELOPMENT
❖History Of Steel Moment Frame

31. 31
•Manydifferenttypesoffractureswerealso
discovered,themajorityinitiatingwherethe
bottombeamflangejoinedthecolumnflange.
•TheSACresearch,conductedatacostof$12
millionovereightyears,resultedinthebasisfor
thecurrentdesignprovisionsformomentframes
containedinAISC341,AISC358,andAWSD1.8.
HISTORY OF SPECIAL MOMENT FRAME DEVELOPMENT
❖History Of Steel Moment Frame

32. 32
•Typically,butnotalways,fractures
initiatedatthecompletejointpenetration
(CJP)weldbetweenthebeambottom
flangeandcolumnflange(Figure1-2).
•Onceinitiated,thesefracturesprogressed
alonganumberofdifferentpaths,
dependingontheindividualjoint
conditions.
HISTORY OF SPECIAL MOMENT FRAME DEVELOPMENT
❖History Of Steel Moment Frame

33. 33
STEEL MOMENT FRAMES LIMITATIONS
1.ORDINARYMOMENTFRAMES
•AISC341§E1
•light,single-storystructuresandlow-riseresidentialstructuresinallSDC
•permittedwithoutrestrictioninSDC-A,B,andC
2.INTERMEDIATEMOMENTFRAMES
•AISC341§E2
•permittedwithoutrestrictioninSDC-A,B,andC
•InSDC-D,arepermittedforstructuresupto35feet(11m)inheight
•InSDC-EandF,arepermittedforlight,single-storystructuresonly
3.STEELSPECIALMOMENTFRAMES
•AISC341§E3
•arepermittedwithoutrestrictioninallSDC
Recommendations
•arerequiredaspartoftheseismicforce-resistingsysteminSDC-D,E,andFformoststructuresexceeding
160feet(49m)inheight
❖SteelMoment Frames Types Limitations

34. 34
•Impracticaltodesignstructurestoresistsuchseverebutrareearthquakes
withoutdamage.
•Thebuildingcodeshaveadoptedadesignphilosophyintendedtoprovide
safetybyminimizingtheriskofcollapse.
•Inelasticbehaviorisintendedtobeaccommodatedthroughtheformationofplastichingesinbeamsat
beam-columnjoints,aswellasatcolumnbases.
•Plastichinginginbeamsandcolumnscanbeaccompaniedbylocalbucklingofbeamandcolumnflangesor
webs.
•Inrecognitionofthehighlyductileinelasticbehaviorofpanelzonesandtheabilityofthisbehaviorto
minimizethedamagetobeams,AISC341encouragesdesigntoaccommodatebalancedyieldingbetween
plastichingezonesinbeamsandthepanelzones.
STEEL MOMENT FRAME SEISMIC BEHAVIOR
0. Introduction

35. 35
•Whenbucklingbecomesexcessive,strengthlossandultimatelyfractures
associatedwithlow-cyclefatiguewilloccur.
•Theuseofhighlycompactsectionsformembersintendedtoexperience
hinging,minimizesthepotentialforstrengthlossandfracturingatdeformation
levelslikelytooccurinresponsetoMCERshaking.
STEEL MOMENT FRAME SEISMIC BEHAVIOR
1. Beam behavior
•Provisionoflateralbracinginzonesof
anticipatedplastichingingisrequiredto
avoidlateraltorsionalbucklingandthe
strengthlossassociatedwiththatbehavior
mode.

36. 36
•Transfertheyield-levelstressesandstrainsthatdevelopinthebeamtothecolumn.
•Failuremodes:
1.Fracturesinoraroundwelds
2.Fracturesinhighlystrainedbasematerial
3.Fracturesatweldaccessholes
4.Netsectionfracturesatboltholes
5.Shearingandtensilefailuresofbolts
6.Boltbearingandblockshearfailures
•AISC341requiresdemonstrationbyconformancewithprequalifieddetailsorthroughprototypetesting:
1.atleast+/-0.04radiansoftotalrotation
2.NostrengthlossassociatedwiththeseORotherfailuremodeswhensubjectedtoaspecified
loadingconsistingofrepeatedcyclesofincreasingdisplacement.
STEEL MOMENT FRAME SEISMIC BEHAVIOR
2. Beam-to-column Connections

37. 37
•Consistofthatportionofthecolumnboundedbythe
topandbottombeamflanges,resistssignificant
shear,tension,andcompressionforcesfromthe
beamsframingintothecolumn.
•Potentialfailuremodesincludewebcompressive
buckling,webshearbuckling,and,ifdoublerplates
areusedtoreinforcethepanelzone,fractureat
welds.
•AISC341designprocedurescontrolthesebehaviors
throughrequirementsforminimumshearstrength,
provisionofstiffenerplatesoppositebeamflanges,
andcontrolofweldingdetails.
STEEL MOMENT FRAME SEISMIC BEHAVIOR
3. Joint Panel Zones

38. 38
•Doublerplateisneededtolocallystrengthenthecolumnweb.
•Addingdoublerplatesisexpensivebecauseofthesignificantshop
fabricationtimethatisneededtopreparetheplateandweldit
intothecolumnweb.
•Aruleofthumbthatcommonlyappliesformosttypicalmoment
frameconfigurations,storyheightsofapproximately5m,and
beamspansofapproximately10m,isasfollows:
•ifthedesignercanincreasetheweightperfootofthecolumnby
lessthan150kg/mandavoidtheneedfordoublerplates,thecost
oftheframewillbereduced
STEEL MOMENT FRAME SEISMIC BEHAVIOR
4. Doublerplate

39. 39
•Exceptatrestrainedcolumnbases,whereplastichingingislikelyto
occur,columnsaredesignedtobehaveinanessentiallyelastic
manner.
•Thisisaccomplishedthroughrequirementsthatcolumnsbestronger
inflexurethanbeamsconnectedtothecolumnsatthesamejoint.
•Columnscanexperiencesignificantinelasticrotationsinresponseto
severeshaking,resultinginexcessivelocalbucklingandlateral-
torsionalbuckling.
•Tominimizethispotential,columnsmusthaveadequateaxial
strength,compactness,andlateralbracingtowithstandtheaxial
forcesassociatedwithformationoffullframeyieldmechanisms.
STEEL MOMENT FRAME SEISMIC BEHAVIOR
5. Columns

40. 40
•Inmultistoreybuildings,itisveryconvenienttosplicethecolumn
justabovethefloor.
•Multi-Storeystructuresgenerallyrequirethatthecolumnsbe
‘spliced’inordertoextendtheirlengthforthefullheightofthe
structure.
•Splicesmaybeeitherboltedorwelded
•Potentialfailuremodesatcolumnsplicesaresimilartothose
enumeratedforbeam-tocolumnconnections.
•theexpectedflexuralstrengthofthesmallercolumncross
sectionbedevelopedatcolumnsplices,eitherthroughtheuse
ofcompletejointpenetrationgrooveweldsorthroughother
meansthatcanprovidesimilarstrength.
STEEL MOMENT FRAME SEISMIC BEHAVIOR
6. Column Splices

41. 41
•Manysteelspecialmomentframeconnectionsincludeagrooveweld
betweenthebeamflangesandthecolumnflange.
•thisjointismadewithasinglebevelweldthatisdetailedwithweld
backingacrossthewidthoftheflange,withtheweldbeingmadein
theflatposition.
•Thebackingistypicallyasteelbar,1inchwideby3/8inchthick(10
mm).
•Toaccommodatethisbackingandtoprovideaccessforthewelderto
maketheweldatthebottomflange,aweldaccessholeisprovided.
•WeldsmaybeclassifiedaseitherCompleteJointPenetration(CJP)or
PartialJointPenetration(PJP).
•CJPweldsextendcompletelythroughthethicknessofcomponents
joined.
•ACJPweldtransmitsthefullload-carryingcapacityofthestructural
componentsjoined,andisimportantforseismicsafety.
STEEL MOMENT FRAME SEISMIC BEHAVIOR
8. Weld Access Holes

42. 42
•Theydonothavestructuralwallsordiagonalbraces.
•Imposesmallerforcesonfoundationsthandootherstructuralsystems.
•Providearchitecturalfreedomindesign,permittingopenbaysand
unobstructedviewlines.
FEATURES OF STEEL MOMENT FRAME
1. Advantages
2. Disadvantages
•canbemorecostlytoconstructthanbracedframeorshearwallstructures.
•Theaddedcostresultsfromtheuseoflargersectionsinmomentframes
thaniscommoninbracedstructuresandmorelabor-intensiveconnections.
•drift-sensitivenonstructuralcomponents,suchascladdingandglazing,can
experiencemoredamageinthesestructurescomparedwithother
structuraltypes

43. 43
•ThereducedseismicforcesdecreasesprogressivelyfromOMRFtoIMRFto
SMRF.
•Theaddedlevelofdetailingrequiredforthebetter-performingsystemscan
significantlyincreaseconstructioncost.
•lateraldriftoftencontroltheselectionofmomentframemembersizes
•Thereducedrequiredstrengthassociatedwiththemoreductilesystemsdo
notnecessarilytranslatetosavingsinmembersizesorframeweight.
•FortallbuildingsinSDC-D,E,andF,usedualsystems,inwhichsteelspecial
momentframescapableofprovidingatleast25%oftherequiredlateral
strengthareusedincombinationwithshearwallsorbracedframes.
•Thedualsystemallowseconomicalcontroloflateraldrift
SteelMoment Frames Features
FEATURES OF STEEL MOMENT FRAME

44. 44
FRAME PROPORTIONING
•factorsaffectingsteelSMRFmembersize:
1.needtocontroldesigndriftsbelowspecifiedlimits
2.needtoavoidP-Dinstabilities
3.needtoproportionstructurestocomplywiththestrong-column/weak-beamcriteriaofAISC341§E3.4a
•Useofdeepsectioncolumns(ex:W24s,W36s,andbuilt-upboxsections)
1.economicalchoice
2.achievementofdriftcontrol
3.achievementstrongcolumn/weak-beamrequirements
•deepwideflangesections,particularlythosewithlighterweights
1.susceptibletoundesirablelocalandlateral-torsionalbuckling.
•Theperformanceofdeepcolumnsectionsisthesubjectofongoingresearch.
SteelMoment Frame Proportioning

45. 45
3.5 Connection Type Selection
•Prequalifiedconnectionshavebeendemonstratedtobeacceptable.
•connectionprequalificationscontainedinthestandardareacceptabletomost
buildingofficials.AISC341
•Eachprequalifiedconnectionhasuniquelimitsofapplicabilityassociatedwith
membertype,depth,andweight.
•noteveryconnectioncanbeusedinthesameapplications.
•Sometypesofconnection:
1.Thereducedbeamsection
2.endplateconnection
3.weldedunreinforcedflange-weldedweb,
4.anddouble-teeconnections.
AISC Prequalified Connections

46. 46
AISC Prequalified Connections

47. 47
COMPOSITE MOMENT FRAME
DESIGN REQUIREMENTS AND ASSUMPTIONS
PART 3

48. 48
•C-SMFsusuallyconsistofCFTcolumns,wideflangesteelbeams,andrigid
beam-to-columnconnections.
•C-SMFshavebeenwidelyusedaroundtheworld,forexample,in
1.TwoUnionSquareinSeattle,USA;
2.ShimizuSuperHighRiseinTokyo,Japan
•C-SMFshaveexcellentearthquakeresistance
•AISC360-16(2016c)providesdesignprovisionsforCFTmembers,including
•steeltubeslendernesslimits(i.e.,limitsonthesteeltubewidth-to-
thicknessratio)tocategorizeCFTmembersintocompact,noncompact,
andslender.
•designequationsforestimatingthestrengthofCFTmembersas
columns,beams,andbeam-columns.
COMPOSITE SPECIAL MOMENT RESISTING FRAME
❖Wide Flange Beam To Concrete-filled Steel Column Connections

49. 49
•Rigidbeam-to-columnmomentconnectionsshouldbedesignedtoresisttheforces
transferredfromtheconnectedmemberswithnegligiblerotation.
•Theseforcesproduceshearinthepanelzone,whichisresistedbyelementswithinthe
panelzone(e.g.,concreteinfill,steeltubewebs,andsteelbeamweb).
•Iftheconnectionisunabletoresistsuchshear,panelzonefailurewilloccurbecauseof
excessivesheardeformations.
•Typicalpanelzoneshearfailuremodesofcompositebeam-to-columnconnections
include
1.shearbucklingofthesteeltubewebs
2.shearyieldingofthebeamwebandsteeltubewebs
3.localizedbearingfailureintheconcrete(Koester2000)
4.diagonalshearcracksintheconcrete(Riclesetal.,2004).
•Thefailuremodesdependontheconnectiontype.
COMPOSITE SPECIAL MOMENT RESISTING FRAME
❖Wide Flange Beam To Concrete-filled Steel Column Connections

50. 50
•AISC341-16(2016b)hasthefollowingrequirementsfor
beam-to-columnconnectionsinC-SMFs:
1.Fullyrestrained(i.e.,rigid)
2.Capableofaccommodatingastorydriftangleofat
least0.04rad
3.Measuredflexuralresistanceoftheconnection,
determinedatthecolumnface,shallequalatleastto
0.80Mpatastorydriftangleof0.04rad,whereMpis
thenominalplasticflexuralstrengthoftheconnected
beam.
COMPOSITE SPECIAL MOMENT RESISTING FRAME
❖Wide Flange Beam To Concrete-filled Steel Column Connections

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•itconsistsofCFTcolumns,wideflangebeams,taperedT-stubs,andhigh-
strengththroughbolts.
•TheT-stubflangewasattachedtothecolumnflangeusingpre-tensioned
highstrengththroughbolts,andtheT-stubstemwasboltedorfilletwelded
tothebeamflange.
•theshearresistanceofDSTconnectionsismainlyprovidedbythesteeltube
websandtheconcretecompressionstrutinthepanelzone.
•ShearistransferredfromthebeamtoCFTcolumnthroughasheartab
connectionweldedtotheCFTcolumnsteelandboltedorweldedtothe
wide-flangedbeamweb.
❖Double Split-tee Connections DstConnection
COMPOSITE SPECIAL MOMENT RESISTING FRAME

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•TwotypesofDSTconnectionsweretested
byRiclesetal.(2004).
1.T-stubstemconnectedtobeam
flangeusinghighstrengthbolts
2.T-stubstemweldedtothebeam
flange.
•Thetestresultsindicatedthatbothtypes
ofconnectioncouldaccommodatestory
driftanglesgreaterthan0.04radwithout
noticeablestrengthdegradation.
•Therefore,theseconnectionssatisfythe
AISC341-16(2016b)requirements.
COMPOSITE SPECIAL MOMENT RESISTING FRAME
❖Double Split-tee Connections DstConnection

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•ThegoverninglimitstatesofDSTconnectionsarelistedasfollows,frommostductile
(desirable)toleastductile:
1.plastichingeformationinbeam,
2.grossyieldingoftheT-stem,
3.netsectionfractureoftheT-stem,
4.compressionoftheT-stemcausedbyflexuralbuckling
5.weldfracturebetweentheT-stemandthebeamflanges,
6.pryingoftheT-stubflanges,
7.boltfractureowingtothepryingactionoftheT-stubflange,
8.panelzoneshearfailure.
•Itshouldbedesignedanddetailedsothatplastichingingoccursinthebeampriorto
anyoftheotherlimitstates.
COMPOSITE SPECIAL MOMENT RESISTING FRAME
❖Double Split-tee Connections DstConnection

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•Thepanelzoneshearstrength(Vn)ofDSTconnectionsforrectangularCFTcolumnsis
contributedfromtwoparts
1.theshearstrengthofsteeltubewallsinthepanelzone(Vtw)
2.theconcretecompressionstrut(Vcs).
•ThedesignequationsproposedbyKoester(2000)wereusedtocalculatethepanelzone
shearzonestrengthasfollows:
COMPOSITE SPECIAL MOMENT RESISTING FRAME
❖Double Split-tee Connections DstConnection

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❖DESIGN EXAMPLE FOR A WELDED DST CONNECTION
ThisexamplepresentsthedesignofaDSTconnectionasaninteriorjointinaC-SMF.
oThewideflangebeamsareASTMA992(2015)wideflangesections(W24×76,Fy=345MPa,Fu=448
MPa,Ry=1.1).
oThebeamdepth(h)is607mm,flangewidth(bf)is228mm,flangethickness(tbf)is17.3mm,andweb
thickness(tbw)is11.2mm.
oTheCFTcolumnsHollowSteelSection(HSS)406.4×406.4×19.1madefromASTMA500(2018)GradeB
steel(Fy=317MPa,Fu=448MPa)andfilledwithnormal-weight,55.2MPaconcrete(f′c).
oA490boltswiththediameter(dbt)of25.4mmareused.
oThedistributeddeadandliveloadsconsideredonthebeamsare12.3kN/mand8.8kN/m,respectively.
oThebeamandcolumnlengthareLb=9,144mmandLc=3,810mm,respectively.
COMPOSITE SPECIAL MOMENT RESISTING FRAME

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❖DESIGN EXAMPLE FOR A WELDED DST CONNECTION
COMPOSITE SPECIAL MOMENT RESISTING FRAME

57. 57
❖DESIGN EXAMPLE FOR A WELDED DST CONNECTION
A14-stepdesignprocedureisproposedasfollows:
•Step1:Calculatetheflexuralandsheardemandsfortheconnectionatthefaceofthe
column,andthenusetheflexuraldemandtocalculatethebeamflangeforcesinthe
DSTconnection.Thesedemandsshouldincludeamaterialoverstrengthfactor,Ry,and
afactortoaccountforpeakconnectionstrength,includingstrainhardening,local
restraint,additionalreinforcement,andotherconnectionconditions,Cpr.
•Step2:Determinethelengthandsizeofweldsrequiredtoresistthebeam
•flangeforcesintheconnection.
•Step3:EstimatetheflangeforceintheT-stubcausedbytheexpectedmomentatthe
faceofthecolumn.
COMPOSITE SPECIAL MOMENT RESISTING FRAME

58. 58
❖DESIGN EXAMPLE FOR A WELDED DST CONNECTION
•Step4:SizetheT-stembasedonlimitstatesofgrosssectionyielding,netsection
fracture,andcompressioncausedbyflexuralbuckling.
•Step5:DeterminethesizeoftheboltsconnectingtheT-stubflangestothecolumn.
•Step6:DetermineaninitialconfigurationoftheT-flange,includingthelayoutofthe
bolts,widthoftheT-stubflanges,andflangethicknesstominimizeoreliminateprying
action.
•Step7:SelectaW-shapeorfinalsizesofbuilt-upplatesfordimensionsoftheT-stub.
•Step8:Checktheconnectionrotationalstiffnesstoensurethattheconnectionis
classifiedasfullyrestrained.
•Step9:ComputethemaximumforceintheT-stubusingactualT-stubdimensionschosen
inStep7.
COMPOSITE SPECIAL MOMENT RESISTING FRAME

59. 59
❖DESIGN EXAMPLE FOR A WELDED DST CONNECTION
•Step10:Back-checkthestrengthoftheweldwiththeactualflangeforcetoensure
theweldhasadequatestrengthtoresisttheactualflangeforce.
•Step11:Back-checkthestrengthoftheT-stemusingthemaximumbeamflange
forcecalculatedinStep9.Thisincludesgrosssectionyielding,netsectionfracture,
andflexuralbucklingstrengthsoftheT-stem.
•Step12:Back-checktheflangestrengthoftheT-stubusingthemaximumbeam
flangeforcecalculatedinStep9.
•Step13:Determinetheconfigurationoftheshearconnectiontotheweb
consideringeccentricloadingonthebolts.
•Step14:CheckpanelzonestrengthusingEquation(3-1).
COMPOSITE SPECIAL MOMENT RESISTING FRAME

60. 60
❖DESIGN EXAMPLE FOR A WELDED DST CONNECTION
•Step10:Back-checkthestrengthoftheweldwiththeactualflangeforcetoensure
theweldhasadequatestrengthtoresisttheactualflangeforce.
•Step11:Back-checkthestrengthoftheT-stemusingthemaximumbeamflange
forcecalculatedinStep9.Thisincludesgrosssectionyielding,netsectionfracture,
andflexuralbucklingstrengthsoftheT-stem.
•Step12:Back-checktheflangestrengthoftheT-stubusingthemaximumbeam
flangeforcecalculatedinStep9.
•Step13:Determinetheconfigurationoftheshearconnectiontotheweb
consideringeccentricloadingonthebolts.
•Step14:CheckpanelzonestrengthusingEquation(3-1).
COMPOSITE SPECIAL MOMENT RESISTING FRAME

61. 61
THANK YOU
Contact meforanyhelp
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62. 62
REFERENCES
✓DesignanddetailingofreinforcedconcretebuildingsbasedonACI
✓Earthquakeengineeringtheoryandimplementation
✓Windandearthquakeresistantbuilding-structuralanalysisanddesign
✓Seismicdesignofsteelspecialmomentframesaguideforpracticingengineers
✓CompositeSpecialMomentFrameswideflangebeamtoconcrete-filledsteelcolumnconnections
✓RecommendedSeismicDesignCriteriaforNewSteelMoment-FrameBuildings
✓AISCLiveWebinarSeriesJuly16,2018
✓AISCPrequalifiedConnectionsforSpecialandIntermediateSteelMomentFramesforSeismic
Applications