外文翻译 - 图文

PerformanceofThree-DimensionalReinforcedConcreteBeam-ColumnSubstructuresunderLossofaCorner

ColumnScenario

KaiQian,A.M.ASCE1;andBingLi2Downloaded from ascelibrary.org by Nanjing University Of Technology on 01/03/16. Copyright ASCE. For personal use only; all rights reserved.Abstract:ThevulnerabilityofconventionalRCstructurestostructuralfailurecausedbythelossofcornercolumnshasbeenemphasizedoverthepastyears.However,thelackofexperimentaltestshasledtoagapintheknowledgeforthedesignofRCbuildingstructurestomitigatethelikelihoodofprogressivecollapsecausedbylosingagroundcornercolumn.Sevenone-thirdscaleRCbeam-columnsubstructuresweretestedtoinvestigatetheirperformance.Thevariablesselectedforthetestspecimensincludedbeamtransversereinforcementratios,typeofdesigndetailing(nonseismicorseismic),andbeamspanaspectratios.Shearfailurewasobservedtohaveoccurredinthecornerjoint,andaplastichingewasformedatthebeamendnearthe?xedsupportinthenonseismicdetailedspecimens.However,plastichingeswerealsoformedinthebeamendneartothecornerjointfortheseismicallydetailedspecimen.Vierendeelactionwasidenti?edasthemajorloadredistributionmech-anismbeforeseverefailureoccurredinthecornerjoint,butacantileverbeamredistributionmechanismdominatedafterthecornerjointsufferedseveredamage.ThetestresultswerecomparedwiththeDepartmentofDefensedesignguidelinestohighlightthede?cienciesoftherecentlyupdatedguidelines.DOI:10.1061/(ASCE)ST.1943-541X.0000630.?2013AmericanSocietyofCivilEngineers.CEDatabasesubjectheadings:Progressivecollapse;Reinforcedconcrete;Beamcolumns;Substructures.

Authorkeywords:Progressivecollapse;Reinforcedconcrete;Corner;Threedimensional;Beam-column;Substructures.

Introduction

ASCESEI7(2010)de?nesprogressivecollapseasthespreadofaninitiallocalfailurefromelementtoelement,whicheventuallyresultsinthecollapseofanentirestructureoradisproportionatelylargepartofit.Inlesstechnicalterms,itisoftenthoughtofasthedominoeffect.ThecollapsesoftheRonanPointTowerinLondonin1968andMurrahFederalBuildinginOklahomaCityin1995havede-monstratedthedisastrousconsequencesofaprogressivecollapse.Topreventprogressivecollapse,astructureshouldhavecontinuitytoofferanalternatepathtoensurethestabilityofthestructurewhenaverticalload-bearingelementisremoved.Designguidelines[DepartmentofDefense(DoD)2005;GeneralServicesAdminis-tration(GSA)2003]haveproposeddesignprocedurestoevaluatethelikelihoodofprogressivecollapseofastructurefollowingthenotionalremovaloftheverticalload-bearingelements.Althoughsigni?cantimprovementswereimplementedintherecentlyupdatedDoDdesignguidelines(2009)[foradetaileddescriptionoftheseupdatedpoints,pleaserefertoStevensetal.(2009)andMarchandetal.(2009)],anumberofdesigncriteriastillneedtobesubjectedtofurtheranalysisandveri?cationwithexperimentaldata.

TobetterunderstandtheperformanceofRCframessubjectedtodifferentmissingcolumnscenarios,severalexperimentaland

ResearchAssociate,SchoolofCivilandEnvironmentalEngineering,NanyangTechnologicalUniv.,Singapore639798(correspondingauthor).E-mail:qiankai@ntu.edu.sg2AssociateProfessor,SchoolofCivilandEnvironmentalEngineering,NanyangTechnologicalUniv.,Singapore639798.

Note.ThismanuscriptwassubmittedonMay18,2011;approvedonJuly20,2012;publishedonlineonAugust10,2012.DiscussionperiodopenuntilSeptember1,2013;separatediscussionsmustbesubmittedforindividualpapers.ThispaperispartoftheJournalofStructuralEngi-neering,Vol.139,No.4,April1,2013.?ASCE,ISSN0733-9445/2013/4-584–594/$25.00.

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1numericalstudieshavebeenconductedinrecentyears.Sasanietal.(2007)conductedaninsitutesttostudytheperformanceofaRCbuildingwithone-way?oorslabssupportedbytransverseframeswhensubjectedtothesuddenremovalofoneofitsexteriorcolumns.ThebehaviorofaRCmomentframesubjectedtothelossofaninteriorcolumnwasalsoinvestigatedbyYietal.(2008).Theef?ciencyofusingcarbon?ber–reinforcedpolymer(CFRP)ret-ro?ttingRCpre-1989frames,whichmaybede?cientinitsconti-nuitysubsequenttothelossofaninteriorcolumn,wasinvestigatedbyOrtonetal.(2009).Thebehaviorofaxiallyrestrainedbeam-columnsubassemblagesunderthescenarioofthelossofacolumnwasstudiedbySuetal.(2010).Theperformanceofexteriorandinteriorbeam-columnsubassemblagesfollowingthelossofoneofthegroundexteriorcolumnswasexperimentallystudiedbyYapandLi(2011)andKaiandLi(2012a),respectively.However,mostofthepreviousresearchstudieswerefocusedontheframessubjectedtothelossofinteriororexteriorcolumnscenarios,whereaslimitedstudieshavebeenconductedforthecaseoflossofcornercolumns.Mohamed(2009)investigatedtheimplementationofDoD(2005)toprotectagainstprogressivecollapseofcorner?oorpanelswhentheirdimensionsexceededthedamagelimitsthroughnumericalsimu-lation.AcasestudyofaRCbuildingwithdifferentbracingcon-?gurationswasanalyzedusinganalternateloadpathmethod.KaiandLi(2012b)experimentallystudiedthedynamicperformanceofsixbeam-columnsubstructuresunderalossofagroundcornercolumnsscenario.Thedynamicresponsesofacceleration,velocity,anddisplacementweredetermined.Moreover,thedynamiceffectsofthebeam-columnsubstructurecausedbysuddenremovalofacornercolumnwereevaluated.Sasani(2008)andSasaniandSagiroglu(2008)conductedaninsitutesttoexaminethedynamicresponseandthepossibilityofaprogressivecollapseofaRCframewhenonecornercolumnandadjacentexteriorcolumnsweresimultaneouslydemolishedbyexplosion.Theyconcludedthatthethree-dimensional(3D)Vierendeelactionofthetransverseandlongitudinalframeswas

J. Struct. Eng., 2013, 139(4): 584-594

Downloaded from ascelibrary.org by Nanjing University Of Technology on 01/03/16. Copyright ASCE. For personal use only; all rights reserved.themajormechanismfortheredistributionofloadsinthestructure.However,theaccuracyofthenumericalresultsisneededtoimproveviacomparingwiththerelatedexperimentalresults.Inaddition,thetremendouscostsoftheinsitutestsmeanthatitisimpossibletosystemicallyinvestigatetheperformanceofRCframesagainstpro-gressivecollapseviathismethod.Therefore,sevenone-thirdscaleRCbeam-columnsubstructuresweredesignedandtestedatNanyangTechnologicalUniversity(NTU),Singapore,toinvestigatetheper-formanceofsubstructuresforprogressivecollapsecausedbylosingoneofthecornercolumns.TheprimaryobjectiveofthispaperistogainabetterunderstandingofthebehaviorofRCsubstructuresunderthescenarioofbeingsubjectedtothelossofoneofitsgroundcornercolumns.Inparticular,thefollowingvariableswerestudied:variationofbeamtransversereinforcementratiointheplastichingeregion,seismicdesigndetailing,designspanlength,andspanaspectratio.TheresultsofthisstudycanbeusedasabasisfortheunderstandingofthebehaviorofRCstructuresforprogressivecollapse.

ExperimentalProgramExperimentalSetup

AsobservedfromMohamed(2009)andKai(2012),mostofthedeformationofatypicalRCframesubjectedtothelossofagroundcornercolumntookplaceinthecornerpanels,whereasthede-formationoftherestofthepanelswasnegligible.Therefore,onetypicalcriticalpanel(cornerpanelinthesecondstory)wasextractedandstudied.AschematicofthetestsetupisshowninFig.1.Thesetupcanbeseparatedintothreecomponents.InComponent1,vertical,axial,androtationalconstraintswereprovidedattheen-largedadjacentcolumnstosimulate?xedboundaryconditionsprovidedbythesurroundingstructuralelements.InComponent2,axialloadinginthecornercolumnbeforethedamagewassimulatedbyapplyingdownwarddisplacementsatthecornercolumnstubthroughahydraulicjackwith600-mmstroke.Boththepreviousnumericalandexperimentalstudies(SasaniandSagiroglu2008)indicatedthatthedirectionofthebendingmomentinthebeamendneartothecornerjoint(BENC)waschangedafterremovalofthecornercolumnandresultedinaconsiderablypositivebendingmoment(tensileatthebottom)beingformedintheBENCaftertheremovalofthegroundcornercolumnasaresultofVierendeelaction.However,asobservedinthedeformationshapeofthecornerjointfromSasaniandSagiroglu(2008),aslighthorizontalmovementaccompaniedtheverticalmovementofthecornerjointafterremoval

ofthegroundcornercolumn,anditindicatedthattherotationalintheBENCwasnotfullyconstrained.Component3wasusedtoapplythispositivebendingmomentintheBENCfortestsubstructures.Fig.2illustratesthedetailingofthesteelassemblyofthiscom-ponent.OnestrongsteelcolumnwasconnectedtothecornerstuboftheRCspecimenusinganchorbolts.Foursteelpinswithhighstrengthandstiffnesswereusedtoapplytheprescribedpartialrotationalandhorizontalconstraintsineachdirection.Inotherwords,thesteelcolumncouldfreelymoveintheverticaldirection,buttherotationalandhorizontalfreedomswerepartiallyrestrained.Theextentofrotationalandhorizontalconstraintsappliedonthecornerjointwasrelatedtotheallowancebetweenthesteelpinandtheholeinthesteelbox(asshowninFig.2),whichwasdesignedwiththeaidofABAQUS.The?nite-elementmodel(FEM)wasvalidatedbycomparingthenumericalresultstothetestresultsattainedbySasanietal.(2007).Thismodelwasusedtopredicttherelationshipofthehorizontalmovementandverticalde?ectionofthecenterofthecornerjointbypushoveranalysis.TheFEMresultindicatesthecenterofthejointjustabovethelostcolumnhasmaximumoutwardhorizontalmovementof～7.2mm(0.28in.),whereastheverticaldisplacement(D1)is～180.0mm(7.09in.).Theallowancebetweenthesteelpinandtheholewasdesignedasfollows:

f?

H1H17:2?8:9?1023??

625t180TVVtD1

V?f350?8:9?1023

?1:56?

22

e1T

d?e2T

Therefore,thedifferencebetweenthediametersofthesteelpintothe

holewas3mm,asillustratedinFig.2.ExperimentalSubstructures

Inthecurrentstudy,thenonseismicandseismic-designed9-storyRCprototypebuildingsweredesignedinaccordancewithSinga-poreStandardCP65(1999)andAmericanConcreteInstitute(ACI)318-08(2008),respectively.Thetestsubjectswereassumedtoberegularframesforeaseofanalyzes.Fig.3presentsbasicstructuralinformationoftheprototypeframeinaccordancewithatypicalnonseismic-designedSpecimenF3.Fortheremainingprototypeframes,thedimensionsandreinforcementdetailsaregiveninTable1.Consideringthespatiallimitationsinthelaboratoryanddif?cultiesoftransportation,one-thirdscaletestswereconducted.

Fig.1.Overviewofaspecimeninpositionreadyfortesting

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J. Struct. Eng., 2013, 139(4): 584-594

Downloaded from ascelibrary.org by Nanjing University Of Technology on 01/03/16. Copyright ASCE. For personal use only; all rights reserved.Fig.2.Detailsofsteelassembly

Fig.3.PlanandelevationviewoftheprototypeframeinaccordancewithSpecimenF3

ThecomparisonsbetweentheprototypeframeswiththemodelframesaregiveninTable1.Itshouldbestressedthattheseismic-designedprototypebuildingwasassumedtobelocatedonasiteclassofD,stiffsoilpro?le;thedesignspectralresponseaccelerationparameters,SDSandSD1,were0.47and0.32,respectively.

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Thedistributeddeadloadontheprototypestructurecausedbythegravityloadofa210-mm-thickslabwas5.1kPa.Thesuper-imposeddeadloadfromceiling,mechanicalductwork,electricalitems,andplumbingwasassumedtobe1.0kPa.Theequivalentadditionaldeadloadsfromtheweightofin-?llwallsandbeams

J. Struct. Eng., 2013, 139(4): 584-594

were2.25and1.59kPa,respectively.Theliveloadwasassumedtobe2.0kPa.Thus,thedesignaxialforceinthecornercolumnofeachspecimenasspeci?edbyDoD(2009)isdeterminedandlistedinTable2.AsillustratedinFig.4,eachtestsubstructureconsistedoftwodoublyreinforcedbeamsconnectedwithacolumnstubatthecornerandtwoenlargedadjacentcolumnsattheedgeswheretherotationalandhorizontalrestraintsonbeamswereapplied.Thecornercolumnstubrepresentingtheremovedcolumnwas200mmsquareforallspecimens.DetailsofthetestsubstructuresaresummarizedinTable2.ThetransversereinforcementratiogiveninTable2wasdeterminedbyEq.(3)

Downloaded from ascelibrary.org by Nanjing University Of Technology on 01/03/16. Copyright ASCE. For personal use only; all rights reserved.designdevelopmentlength.ThedescriptionoftheanchoragedetailsisillustratedinFig.4.MaterialProperties

Thetargetcompressivestrengthofconcreteat28daysofagewas30MPa.Theaveragecompressivestrengthofconcretefc0obtainedfromtheconcretecylindersampleswasfoundtobe31.5,32.1,31.9,32.5,33.1,32.8,and33.3MPaforSpecimensF1,F2,F3,F4,F5,F6,andF7,respectively.Grade250(R6)andGrade460(T16,T13,andT10)steelbarswereusedastransverseandlongitudinalreinforcements,respectively.Table3givesthemeasuredtensilepropertiesofthebarsusedinthetests.Instrumentation

Extensivemeasuringdeviceswereinstalledbothinternallyandexternallytomonitortheresponsesofthetestspecimens.Atotalof100datachannelswereactiveduringthetestingprocess.Aloadcellwasusedtomeasuretheappliedforceonthecornerstub,andthede?ectionshapeofthebeamwasmonitoredthroughLVDTs.Threecompression/tensionloadcellswereinstalledineach?xedsupport.Twoofthemwereverticalandwereusedtodeterminetheverticalreactionforceandthebendingmomentatthe?xedsupport.Theremaininghorizontalone(Item10or11inFig.1)wasusedtomeasurethehorizontalconstraintforceatthe?xedsupport.Tomonitorthehorizontalreactionforceappliedtothecornerjointfromthesteelassembly(Item5inFig.1),twocompression/tensionload

rt?Asv=bvs

e3T

Fig.4illustratesthetypicalreinforcementlayoutoftheSpecimensF2andF3.Theconcretecoverofthebeamandcolumnwas10and20mm,respectively.ForF2,thetransversereinforcementswerehoopstirrupswith135°bends,andtransversereinforcementwasprovidedinthejointregion.Fortheremainingspecimens,nonseismicdetailingwasprovided,transversereinforcementswerehoopstirrupswith90°bends,andnotransversereinforcementwasinstalledinthejointregion.Itshouldbeemphasizedthatadoublycontinuouslongitudinalrebarwasinstalledinthebeambecausescaledspecimensweretestedinthecurrentstudy.TopreventbottomlongitudinalreinforcementbarpulloutattheBENC,90°hookswereused.Thedevelopmentlengthofthehookedbeamtoplongitudinalreinforcementintothe?xedsupportwasgreaterthantheACI318-08(2008)required

Table1.CorelationshipbetweenthePrototypeFramesandtheCorrespondingTestModels

Dimensionsoftheprototypebeams(mm)

LongitudinalrebarintheprototypebeamsBeamT

Test

BeamT

BeamL

Top

Bottom

Top

BeamL

Bottom

BeamT

BeamL

BeamT

BeamL

Dimensionsofthemodel

beams(mm)

Longitudinalrebarinthemodelbeams

F1540330054033002T201T322T201T322T201T322T201T32180310018031004T104T10F2540330054033003T323T323T323T32180310018031004T134T13F3540330054033002T201T322T201T322T201T322T201T32180310018031004T104T10F4540330054033002T201T322T201T322T201T322T201T32180310018031004T104T10F5720330072033002T251T322T251T322T251T322T251T32240310024031004T104T10

180310024031004T104T10F6540330072033002T201T322T201T322T251T322T251T32

F7540330063033002T201T322T201T322T251T322T251T32180310021031004T104T10Note:T325deformedbarof32mmdiameter;T255deformedbarof25mmdiameter;T205deformedbarof20mmdiameter;T135deformedbarof13mmdiameter;T105deformedbarof10mmdiameter;BeamL5longitudinalbeam;BeamT5transversebeam.

Table2.SpecimenProperties(mm)

Elements

SpecimenID

BeamT

BeamL

LongitudinalrebarBeamT(%)

BeamL(%)

Joint

TransversereinforcementBeamT(%)

BeamL(%)

Designaxialload

(kN)

Modi?edDetailedTypeaTypea0.870.87None0.230.2318.6SpecimenF1

SeismicallyDetailedTypeaTypea1.471.470.49%0.950.9518.6SpecimenF2

ControlSpecimenF3TypeaTypea0.870.87None0.310.3118.6Modi?edDetailedTypeaTypea0.870.87None0.720.7218.6SpecimenF4

LongSpanSpecimenF5TypebTypeb0.650.65None0.360.3629.1UnequalSpanSpecimenF6TypeaTypeb0.870.65None0.310.3623.2UnequalSpanSpecimenF7TypeaTypec0.870.75None0.310.3623.2

Note:Typea,clearspan52,175mm,crosssection51803100;Typeb,clearspan52,775mm,crosssection52403100;Typec,clearspan52,775mm,crosssection52103100;BeamL5longitudinalbeam;BeamT5transversebeam.

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J. Struct. Eng., 2013, 139(4): 584-594