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土木工程受弯钢框架结点在变化轴向荷载和侧向位移的作用下的周期性行为大学毕业论文外文文献翻译及原文

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受弯钢框架结点在变化轴向荷载和侧向位移的作用下的周期性行为

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2017.02.14

土木工程建筑外文文献及翻译

Cyclicbehaviorofsteelmomentframeconnectionsundervaryingaxialloadandlateraldisplacements

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.

 2. AnalyticalmodelofCGMRF

Nonlinearstaticpushoveranalysiswasconductedonatypicalone-baymodeloftheCGMRF.Fig.2showsthedimensionsandthevarioussectionsofthe10in）andthe254mm（11/8inmodel.Thelinkflangeplateswere28.5mm183/4in）.TheSAP2000computer476mm（3/8inwebplatewas9.5mmprogramwasutilizedinthepushoveranalysis[5].Theframewascharacterizedasfullyrestrained（FR）.FRmomentframesarethoseframesfor1170whichnomorethan5%ofthelateraldeflectionsarisefromconnectiondeformation[6].The5%valuerefersonlytodeflectionduetobeam–columndeformationandnottoframedeflectionsthatresultfromcolumnpanelzonedeformation[6,9].

 Theanalysiswasperformedusinganexpectedvalueoftheyieldstressandultimatestrength.Thesevalueswereequalto372MPa（54ksi）and518MPa（75ksi）,respectively.Theplastichinges’load–deformationbehaviorwasapproximatedbythegeneralizedcurvesuggestedbyNEHRPGuidelinesfortheSeismicRehabilitationofBuildings[6]asshowninFig.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.Sincetheinclinationangleoftheaxialactuatordoesnotexceed,thereforePaxialisapproximatelyequaltoP[4].However,thelateral3.0component,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 measuredtensilecou