外文翻译钢板包裹的钢筋混凝土柱受冲力影响下的性能.docx
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外文翻译钢板包裹的钢筋混凝土柱受冲力影响下的性能.docx
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外文翻译钢板包裹的钢筋混凝土柱受冲力影响下的性能
中文7700字,5400单词,2.5万英文字符
出处:
GriffithMC,WuYF,OehlersDJ.BehaviourofSteelPlatedRCColumnsSubjecttoLateralLoading[J].AdvancesinStructuralEngineering,2005,8(4):
333-348.
原文
BehaviourofSteelPlatedRCColumnsSubjecttoLateralLoading
GriffithMC,WuYF,OehlersDJ.
Abstract:
ThemainfocusofthispaperistodescribethebehaviourofRCcolumnsthatare
retrofittedwithanalternativetechniqueto“jacketing”orwrapping.Thisnewtechniqueconsistsofattachingsteelplatestothetlexuralfacesofaconcretecolumnusingbolts.Itisenvisagedthatthistechniquewouldbesuitableprimarilyforcolumnshavingrectangularcross-sectionsandinsituationswherelateralloadinginducespredominatelyasingleplaneofbending(asopposedtobiaxialbending).Effectivenessofthisnewtechniquehasbeendemonstratedbyexperimentaltestingandnumericalsimulations.Thispaperstudiesthemechanismofthenewretrofitscheme,howitworks,andthebehaviourofcolumnsretrofittedusingsuchascheme,aswellastheimportantparametersthataffecttheresponseoftheretrofittedcolumns.Thisstudyformsthebasisforthedesignoftheplateretrofittingsystem.
Keywords:
reinforcedconcrete,columns,numericalmodel,retrofitting,partialinteraction,slip.
1.INTRODUCTION
Theoreticalandexperimentalstudieshavedemonstratedthatexternaljacketingcanbehighlyeffectiveinpreventingexistingcolumnsfromprematureshear,lapspltceorflexuralfailureinthecaseofcircularcolumns.Therefore,thiskindofretrofittingworkhasalreadybeenwidelyusedinengineering(Chaietal.1991,1994;Priestleyetal.1994a,b).However,itisnotquiteasclear-cutforrectangularRCcolumnswherethesuccessoftheretrofitproceduredependson
thedegreetowhichjacketingincreasesconfinement.Forexample,Park(2001)states“Arectangularthinsteeljacketwouldnotbesoeffective,duetothesidesbowingoutwhendilationoftheconcreteoccursduringamajorearthquake,resultinginconfinementappliedmainlyinthecolumncorners”.Althoughrectangularjacketingcanstillbeeffectiveincertaincircumstances,therelativepoorperformanceofrectangularjacketsinconfiningtheconcretecorehasbeenexperimentallyverified(Chaietal.1990;Mirmiranetal.1998,2000;Pessikietal.2001)andTheriaultandNeale(2000)concludedthattheconfinementeffectivenessbyFRP(FibreReinforcedPolymer)wrappingisfarlessforrectangularcolumnsthanitisforcircularcolumns.
Effortstoimprovetheconfinementeffectivenessrectangularjacketshavebeenreportedintheliterature.Onetechniquewastoenhancetheout-of-planflexuralstiffnessofthejacketbyusingadditionalstiffenersinthecross-section.However,testresultsshowedthattheimprovementwasnotsatisfactory(Chaietal.1990).Theuseofanchorboltstoenhancetheconfinementfromrectangularsteeljacketwasshown(Aboutahaetal.1996)toalsoprovidelimitedimprovement.Anothertechniqueusedforrectangularcolumnjacketingemploysanellipticalshapedjacket.ResearchworkshasshownthatthistechniqueishighlyeffectiveforretrofittingRCcolumnswithrectangularshapedcross-sections(Priestleyetal.1994b,1995;TengandLam2002).Nevertheless,changingsquareorrectangularshapedcolumnsectionstocircularorellipticalsectionsbycircularorellipticaljacketingisnotalwaysdesirableorpracticalinengineering,especiallywherespaceislimitedasinbuildingstructures.
Therehasbeenmuchresearchintotheuseofadvancedcompositematerialssuchasfiberglassandcarbonfiberjackets/wrappingtoreplacesteeljacketsinrecentyears(Katsumataetal.1988;Saadatmaneshetal.1994,1996;PriestleyandSeible1995;Seibleetal.1997;XiaoandMa1995,1997;MirmiranandShahawy1997;HannaandJones1997;Xiaoetal.1999;Liuetal.2000;Pantelidesetal.2000;Karbhari2001;TheriaultandNealc2000;Yaoetal.2001;LauandZhou2001;Pessikietal.2001;ParvinandWang2001;LamandTeng2003a,b;TengandLam2004).Nevertheless,FRPjacketsliketheirsteelcounterparts,relyontheirabilitytoincreasetheconfinementoftheconcretecolumnsothatitsmaterialbehaviourbeyondthepeakcompressivestresspointisimproved.
Incontrastto“jacketing”retrofitschemes,theformofcompositeplatingdevelopedbytheauthorsisanewconceptforretrofittingrectangularRCcolumns.Itworks,essentially,bydelayingtheonsetofconcretecrushingthroughtheadditionofexternalsteelplatingthatactsonlyincompressionontheflexuralfacesoftheconcretecolumn.Bydelayingconcretecrushing,additionalcurvaturecanbesustainedbythecolumnbeforesubstantiallossofstrengthoccurs,resultinginsubstantiallyincreaseddisplacement/driftcapacity.Detailsofthenewretrofitschemearedescribedinthenextsection.(Note:
platebucklingofside-platedconcretebeamscanbepreventedthroughjudiciouschoiceofplatethicknessandboltspacing(Smithetal.1999).Itisnotafocusofthispaperandwillnotbediscussedfurther.)
2.RETROFITSCHEMEBYPARTIALINTERACTIONPLATING
AschematicofthenewschemeisgiveninFigurelwherealengthofcolumnbetweenitsendandmidheightisshown.Steelplatesintheshapeofan“L”(asinFigurel(a)areboltedtoboththetensionandcompressionfacesofthecolumnandalsotothefoundationorbeam/slab(Figurel(a)andl(d)).Thenovelaspectofthisretrofitsolutionisthattheplateonthetensionfacecanbemadetoattractverylittletensionforce,intheplastichingezoneatthebaseofthecolumn,bypositioningtheboltsawayfromthejoint(Figurel(b),l(c)).Ontheotherhand,theplateonthecompressionfacewillattractsignificantcompressiveforceduetothehighcompressionstiffnessoftheplates’endbearingcondition(Figurel(b)).Thus,thecrushingofconcreteisdelayedsubstantiallynotbyincreasedconcretecompressivestrengthduetoincreasedconfinementbutratherbyvirtueoftransferringthecompressionloadfromtheconcretetothesteelplate.Thishasthepotentialtosignificantlyincreaseeitherthestrengthortheductilityorbothofaconcretecolumn.
Themotivationforthisalternativeretrofitconceptisthatsubstantiallyimprovedconfinementthroughjacketingisnotalwaysachievableforrectangularcross-sections.Furthermanyconcreteframestructuresinlowtomoderateearthquakehazardregionshavebeendesignedpredominatelyforgravityandwindloadingbutmayhaveinsufficientlevelsofdisplacementductilitytowithstandsignificantearthquakeshaking.Inmanyinstances,thecolumnshavesufficientshearstrengthforthecolumnstoreachtheirultimatemomentcapacity.Inthepresentwork,ithasbeenassumedthatcolumnflexureoccursprimarilyina
singleplane.Forexample,bridgepierswhoseflexureinthelongitudinaldirectionisrestrictedduetotheaxialstiffnessofthebridgedeckanddisplacementconstraintsofthebridgeabutments.Inaddition,itisnotunusualtohavecolumnsinabuildingstructureparticipatinginmomentframeactionunderlateralloadingonlyinasingledirection.Forallofthesesituations,itmaybefeasibletoconsiderretrofitonlyforuni-directionalloadingratherthanbi-directionalloading.
Theeffectivenessofthenewretrofitschemehasbeendemonstratedexperimentally(Wuetal.2003).Abriefdescriptionofthetestingisprovidedhere.ThetestconfigurationisillustratedinFigure2(a)withtheaxialloadN=360kNbeingappliedin“forcecontrol”modeandthelateralloadFbeingappliedin“displacementcontrol”mode.Inordertogettwotestsfromeachspecimen,oneendwastemporarilystrengthenedbysandwichingthecolumnbetweenlargesteelchannelsections(Figure2(b))sothatthedeformationsduetotheloadingoccurredonlyintheoppositeend.Thereinforcementdetailsforthecolumnsconsistedoffour16mmdeformedbarsand10mmstirrupsat100mmspacingasshowninFigure2(c).Theretrofitschemedetailsforthetestcolumns(giveninTable1)consistedofboltingeither6mmor12mmthicksteelplateontothetensionandcompressionfacesofthecolumns.TheboltswereadhesivelyattachedtothecolumnusingHiltiHIT-HY150adhesive.Theinteractionorshearbetweentheboltsandthesteelplatewastransmittedbybearing.Theholesinthesteelplatewere0.2mmgreaterthanthediameterofthebolts.Thesteelplatejustsatonthecolumnbaseandnoothermeasurewasusedtopreventlocalconcretecrushingatbaseandbucklingofsteelplate.FormoredetailsofthetestinganddesignoftheplateandboltingpatternrefertoWu(2002)andWuetal(2003).
PlotsofthelateralloadFversussideswaydeflection∆arepresentedinFigure3and
theresultsaresummarizedinTable2.Itshouldbenotedthatamoreuseful,non-dimensional,variableforexpressingthesideswayresponseisintermsof“drift”,definedhereas∆
dividedbythecolumnheightof1.218m.ThedriftresponseisalsoshowninFigure3onthetophorizontalaxis.Tocomparetheresponseofthethreecolumns,itisconvenientthentousedisplacementductility,definedbyEqn1,
µ∆=∆u∆y
(1)
where∆y
istheyielddisplacement(thepointwherethetensilereinforcementfirstyields
andthemaximumstrengthisreached),and
∆uisthelateraldisplacementatthepointwhere
thelateralresistanceforceequals80%ofthemaximumlateralforce.ThedisplacementductilityfactorsforthethreecurvesinFigure3arelistedinTable2whereitcanbeseenthatboththeplatedcolumnshadgreaterdisplacementductilitythantheunplatedcolumn.Similarbehaviourwasobservedinthecyclicloadingtests(Figure4)wherethe6mmplatedcolumn(4ACP6)wassignificant
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