土木工程外文翻译.docx
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土木工程外文翻译.docx
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土木工程外文翻译
附件2:
外文原文(电子或复印件)
Cyclicbehaviorofsteelmomentframe
connectionsundervaryingaxialloadandlateraldisplacements
Abstract:
Thispaperdiscussesthecyclicbehavioroffoursteelmomentconnectionstestedundervariableaxialloadandlateraldisplacements.Thebeamspecim-ensconsistedofareducedbeamsection,wingplatesandlongitudinalstiffeners.Thetestspecimensweresubjectedtovaryingaxialforcesandlateraldisplace-mentstosimulatetheeffectsonbeamsinaCoupled-GirderMoment-ResistingFramingsystemunderlateralloading.Thetestresultsshowedthatthespecim-ensrespondedinaductilemannersincetheplasticrotationsexceeded0.03radwithoutsignificantdropinthelateralcapacity.Thepresenceofthelongitudin- alstiffenerassistedintransferringtheaxialforcesanddelayedtheformationofweblocalbuckling.
1.Introduction
Aimedatevaluatingthestructuralperformanceofreduced-beamsection
(RBS)connectionsunderalternatedaxialloadingandlateraldisplacement,fourfull-scalespecimensweretested.ThesetestswereintendedtoassesstheperformanceofthemomentconnectiondesignfortheMosconeCenterExp-ansion under the DesignBasisEarthquake(DBE)andtheMaximumConsideredEarthquake(MCE).PreviousresearchconductedonRBSmomentconnections[1,2]showedthatconnectionswith RBSprofilescanachieverotationsinexcessof0.03rad.However,doubtshavebeencastonthequalityoftheseismicperformanceoftheseconnectionsundercombined axialandlateralloading.
TheMosconeCenterExpansionisathree-story,71,814m2(773,000ft2)structurewithsteelmomentframesasitsprimarylateralforce-resistingsystem.AthreedimensionalperspectiveillustrationisshowninFig.1.Theoverallheightofthebuilding,atthehighestpointoftheexhibitionroof,isapproxima-tely35.36m(116ft)abovegroundlevel.Theceilingheightattheexhibitionhallis8.23m(27ft),andthetypicalfloor-to-floorheightinthebuildingis11.43m(37.5ft).ThebuildingwasdesignedastypeIaccordingtotherequi-rementsofthe1997UniformBuildingCode.
TheframingsystemconsistsoffourmomentframesintheEast–Westdirect-ion,oneoneithersideofthestairtowers,andfourframesintheNorth–Southdirection,oneoneithersideofthestairandelevatorcoresintheeastendandtwoatthewestendofthestructure[4].Becauseofthestoryheight,thecon-ceptoftheCoupled-GirderMoment-ResistingFramingSystem(CGMRFS)wasutilized.
Bycouplingthegirders,thelateralload-resistingbehaviorofthemomentframingsystemchangestoonewherestructuraloverturningmomentsareresistedpartiallybyanaxialcompression–tensioncoupleacrossthegirdersystem,ratherthanonlybytheindividualflexuralactionofthegirders.Asaresult,astifferlateralloadresistingsystemisachieved.Theverticalelementthatconnectsthegirdersisreferredtoasacouplinglink.Couplinglinksareanalogoustoandservethesamestructuralroleaslinkbeamsineccentricallybracedframes.Couplinglinksaregenerallyquiteshort,havingalargeshear-to-momentratio.
Underearthquake-typeloading,theCGMRFSsubjectsitsgirderstowariab-bleaxialforcesinadditiontotheirendmoments. Theaxialforcesin the
Fig.1.MosconeCenterExpansionProjectinSanFrancisco,CA
girdersresultfromtheaccumulatedshearinthelink.
Fig2. AnalyticalmodelofCGMRF
Nonlinearstaticpushoveranalysiswasconductedonatypicalone-baymodeloftheCGMRF.Fig.2showsthedimensionsandthevarioussectionsofthemodel.Thelinkflangeplateswere28.5mm254mm(11/8in10in)andthewebplatewas9.5mm476mm(3/8in183/4in).TheSAP2000computerprogramwasutilizedinthepushoveranalysis[5].Theframewascharacterizedasfullyrestrained(FR).FRmomentframesarethoseframesfor1170whichnomorethan5%ofthelateraldeflectionsarisefromconnectiondeformation[6].The5%valuerefersonlytodeflectionduetobeam–columndeformationandnottoframedeflectionsthatresultfromcolumnpanelzonedeformation[6,9].
Theanalysiswasperformedusinganexpectedvalueoftheyieldstressandultimatestrength.Thesevalueswereequalto372MPa(54ksi)and518MPa(75ksi),respectively.Theplastichinges’load–deformationbehaviorwasapproximatedbythegeneralizedcurvesuggestedbyNEHRPGuidelinesfortheSeismicRehabilitationofBuildings[6]asshownin.
Fig.3.△ywascalcu- latedbasedonEqs.(5.1)and(5.2)from[6],asfollows:
P–Mhingeload–deformationmodelpointsC,DandEarebasedonTable5.4from[6]for
△ywastakenas0.01radperNote3in[6],Table5.8.Shearhingeload-load–deformationmodelpointsC,DandEarebasedonTable5.8[6],LinkBeam,Itema.AstrainhardeningslopebetweenpointsBandCof3%oftheelasticslopewasassumedforbothmodels.
Thefollowingrelationshipwasusedtoaccountformoment–axialloadinteraction[6]:
whereMCEistheexpectedmomentstrength,ZRBSistheRBSplasticsectionmodulus(in3), istheexpectedyieldstrengthofthematerial(ksi),Pistheaxialforceinthegirder(kips)and istheexpectedaxialyieldforceoftheRBS,equalto (kips).TheultimateflexuralcapacitiesofthebeamandthelinkofthemodelareshowninTable1.
Fig.4showsqualitativelythedistributionofthebendingmoment,shearforce,andaxialforceintheCGMRFunderlateralload.Theshearandaxialforceinthebeamsarelesssignificanttotheresponseofthebeamsascomparedwiththebendingmoment,althoughtheymustbeconsideredindesign.Thequalita-tivedistributionofinternalforcesillustratedinFig.5isfundamentallythesameforbothelasticandinelasticrangesofbehavior.Thespecificvaluesoftheinternalforceswillchangeaselementsoftheframeyieldandinternalfor- cesareredistributed.ThebasicpatternsillustratedinFig.5,however,remainthesame.
Inelasticstaticpushoveranalysiswascarriedoutbyapplyingmonotonically
increasinglateraldisplacements,atthetopofbothcolumns,asshowninFig.6.AfterthefourRBShaveyieldedsimultaneously,auniformyieldinginthewebandattheendsoftheflangesoftheverticallinkwillform.Thisistheyieldmechanismfortheframe,withplastichingesalsoformingatthebaseofthecolumnsifthey arefixed.ThebaseshearversusdriftangleofthemodelisshowninFig.7.Thesequenceofinelasticactivityintheframeisshownonthefigure.Anelasticcomponent,alongtransition(consequenceofthebeamplastichingesbeingformedsimultaneously)andanarrowyieldplateaucharacterizethepushovercurve.
Theplasticrotationcapacity,qp,isdefinedasthetotalplasticrotationbeyondwhichtheconnectionstrengthstartstodegradebelow80%[7].ThisdefinitionisdifferentfromthatoutlinedinSection9(AppendixS)oftheAISCSeismicProvisions[8,10].UsingEq.
(2)derivedbyUangandFan[7],anestimateoftheRBSplasticrotationcapacitywasfoundtobe0.037rad:
FyfwassubstitutedforRy•Fy[8],whereRyisusedtoaccountforthediffer-ence betweenthenominalandtheexpectedyieldstrengths(Grade50steel,Fy=345MPaandRy=1.1areused).
3.Experimentalprogram
Theexperimentalset-upforstudyingthebehaviorofaconnectionwasbasedonFig.6(a).Usingtheplasticdisplacementdp,plasticrotationgp,andplasticstorydriftangleqpshowninthefigure,fromgeometry,itfollowsthat:
And:
inwhichdandgincludetheelasticcomponents.Approximationsasaboveareused forlargeinelasticbeamdeformations.ThediagraminFig.6(a)suggestthatasub assemblagewithdisplacementscontrolledinthemannershowninFig.6(b)can representtheinelasticbehaviorofatypicalbeaminaCGMRF.
Thetestset-upshowninFig.8wasconstructedtodevelopthemechanismshown inFig.6(a)and(b).Theaxialactuatorswereattachedtothree 2438mm×1219mm×1219mm(8ft×4ft×4ft)RCblocks.Theseblockswere tensionedtothelaboratoryfloorbymeansoftwenty-four32mmdiameterdywidag rods.Thisarrangementpermittedreplacementofthespecimenaftereachtest.
Therefore,theforceappliedbytheaxialactuator,P,canberesolvedintotwoorthogonalcomponents,PaxialandPlateral.Sincetheinclinationangleoftheaxialactuatordoesnotexceed3.0,thereforePaxialisapproximatelyequaltoP[4].However,thelateralcomponent,Plateral,causesanadditionalmomentatthebeam-tocolumnjoint.Iftheaxialactuatorscompressthespecimen,thenthelateralcomponentswillbeaddingtothelateralactuatorforces,whileiftheaxialactuatorspullthespecimen,thePlateralwillbeanopposingforcetothelateralactuators.Whentheaxialactuatorsundergo
axialactuatorsundergoalateraldisplacement_,theycauseanadditionalmomentatthebeam-to-columnjoint(P-△effect).Therefore,themomentatthebeam-tocolumnjointisequalto:
whereHisthelateralforces,Listhearm,Pistheaxialforceand_isthelateraldisplacement.
Fourfull-scaleexperimentsofbeamcolumnconnectionswereconducted.
ThemembersizesandtheresultsoftensilecoupontestsarelistedinTable2
AllofthecolumnsandbeamswereofA572Grade50steel(Fy 344.5MPa).Theactualmeasuredbeamflangeyieldstressvaluewasequalto372MPa(54ksi),whilethe ultimatestrengthrangedfrom502MPa(72.8ksi)to543MPa(78.7ksi).
Table3showsthevaluesoftheplasticmomentforeachspecimen(basedon measuredtensilecoupondata)atthefullcross-sectionandatthereducedsectionat mid-lengthoftheRBScutout.
Thespecimensweredesignatedasspecimen1throughspecimen4.TestspecimensdetailsareshowninFig.9throughFig.12.Thefollowingfeatures
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