Improving shear capacity of existing RC beams using external

粘钢加固钢筋混凝土梁斜截面

EngineeringStructures27(2005)

781–791

/locate/engstruct

ImprovingshearcapacityofexistingRCbeamsusing

externalbondingofsteelplates

SinanAltin ,ÖzgürAnil,M.EminKara

DepartmentofCivilEng.,GaziUniversity,Maltepe,06570Ankara,Turkey

Received8October2003;receivedinrevisedform7December2004;accepted21December2004

Availableonline24February2005

Abstract

Variousmethodsaredevelopedforstrengtheningreinforcedconcretebeamsagainstshear.Strengtheningofreinforcedconcretebeamsusingexternalboundingofsteelplateswasoneofthepopularresearchareasofrecentyears.Thisstudypresentstestresultsonstrengtheningshearde cientreinforcedconcretebeamsbyexternalbondingofsteelplates.ElevenreinforcedconcretebeamswithaT-sectionweretestedundermonotonicloadingintheexperimentalprogram.Threemaintypesofsteelmemberswithdifferentarrangementswerebondedtothesideofthebeamwebsalongtheshearspanbyusingepoxy.Thepurposewastoobtainductilebehaviorforshearde cientreinforcedconcretebeams.Thetestresultcon rmedthatallsteelplatearrangementsimprovedthestrengthandstiffnessofthespecimenssigni cantly.Thetensionreinforcementofallstrengthenedreinforcedconcretespecimenswasyielded.Thefailuremodesandductilityofspecimenswereprovedtodifferaccordingtothetypeofthesteelmemberandarrangementalongthebeam.Beamsthatwerestrengthenedwithcontinuoussteelplatealongtheshearspanshowedductile exuralbehavior.©2005ElsevierLtd.Allrightsreserved.

Keywords:Reinforcedconcretebeam;Strengthening;Shear;Epoxy;Steelplate

1.Introduction

Ingeneral,reinforcedconcrete(RC)beamsfailintwomodes: exureandshear.ItiswellknownthattheshearfailureofaRCbeamissuddenandbrittleinnature.Soitislesspredictableandgivesnoadvancewarningpriortofailure.Shearfailureismoredangerousthan exuralfailure.ForthatreasonRCbeamsmustbedesignedtodeveloptheirfull exuralcapacityandassureaductile exuralfailuremodeunderextremeloading.However,manyRCstructuresencountershearproblemsforvariousreasons,suchasmistakesindesigncalculations,improperdetailingoftheshearreinforcement,constructionerrorsorpoorconstructionpractices,changingthefunctionofastructurefromalowerserviceloadtoahigherserviceload,andreductionofthe

Correspondingauthor.Tel.:+903122317400/2248;fax:+90312231

9223.

E-mailaddress:saltin@gazi.edu.tr(S.Altin).

0141-0296/$-seefrontmatter©2005ElsevierLtd.Allrightsreserved.doi:10.1016/j.engstruct.2004.12.012

shearreinforcementsteelareaduetocorrosioninserviceenvironments.

Theknownstrengtheningtechniquesofshearde cientbeamsareasfollows:CFRP,strengtheningwithexternallyappliedclamps,jacketingwithconcretelayersandexternalbondingofsteelplateswithepoxy.Forstrengtheningshearde cientbeams,althoughnumeroustestshavebeencarriedout,andshownthatcompositematerialsareanexcellentoptionforuseasexternalreinforcing,thesteelplatebondingtechniqueisbecomingpreferableforstrengtheningduetoseveraladvantagessuchaseasyconstructionwork,minimumchangeintheoverallsizeofthestructureafterplatebondingandbeinganeconomicaltechnique.Themajorityofresearchtodateonplatebondinghavefocusedon exuralstrengtheningofRCbeamsbybondingsteelplatestobeamsof ts.Previously,veryfewstudieshavebeencarriedoutontheshearstrengtheningofRCbeamsusingwebbondedsteelplates[1–8].TheultimateloadofthestrengthenedRCbeamdependsprincipallyonthecompressivestrengthoftheconcrete,theyield

粘钢加固钢筋混凝土梁斜截面

782S.Altinetal./EngineeringStructures27(2005)

781–791

Fig.1.Reinforcementdetailsofspecimens.

strengthoftheshearandlongitudinalreinforcement,thetensilereinforcementratio,theshearspantodepthratio,thestrengthandratioofstrengtheningmaterialssuchascompositeorsteelplate.AdditionalresearchonsuchstrengtheningtechniqueswasconductedtodeterminetheperformanceofstrengthenedRCbeamsunderdifferentconditions,andtodeterminetheeffectofsteelplatetypesandarrangementsonaRCbeam’sbehaviorandfailuremode.

Thispaperpresentsresultsofanexperimentalstudyconductedonthestrengtheningofshearde cientbeamsbyusingexternalwebbondedsteelplates.Elevenspecimens,oneofwhichwasacontrolspecimenandtheremainingtenofwhichhadde cientshearreinforcement,weretestedinanexperimentalprogram[9–11].RCbeamswithde cientshearreinforcementswerestrengthenedwithdifferentarrangementsofbondedsteelelements.Theaimwastoobtainductile exuralfailureforallstrengthenedspecimens.Theresultsofthetestsonthesebeamswerecomparedwiththatforthecontrolbeam.Theeffectsofthetypeandarrangementofthesteelplatesthatwereusedforstrengtheningonthebehavior,strength,stiffness,failuremodeandductilityofthespecimenswereinvestigated.Theexperimentalresultsarecomparedwithanalyticalpredictions.

2.Experimentalprogram

2.1.Specimensandmaterialproperties

AtotalofelevenT-sectionRCbeamsweretestedintheexperimentalprogram.DimensionsandreinforcementdetailsareshowninFig.1.Thedistancebetweenthesupportswas3800mmandthesameforallspecimens,aswerethecrosssectionalgeometriesandlongitudinalreinforcements.Thelongitudinalreinforcementconsistsofthree20mmdiametersteeldeformedbarsatthebottomandtwo8mmdiameterbarsatthetopofthebeam.Theshearreinforcementconsistedof6mmdiameterclosedstirrups,spacedat300mmcentertocenterthroughoutthebeamexceptforBeam-1.TheclosedstirrupspacingforBeam-1was75mm.Theyieldstrengthsofthelongitudinalsteelbarsatthebottom,topandstirrupswerefsy=414MPa,fsy=304.2MPaandfsy=275MPa,respectively.Table1summarizesthespecimens’properties.Averagecompressivestrengthsofconcreteweredeterminedfromstandardtestsofcylindersthatwerecastfromthesameconcreteaswasusedforthebeams.AscanbeseenfromTable1,theaveragecompressivestrengthsoftheconcretewerethegreaterthan25MPa.Table2showsthemechanicalpropertiesofthereinforcingbarsandsteelplatesusedinthebeams.

Beam-1wasthecontrolspecimenthatwasdesignedsuchthatithadgreatershearstrengththan exuralstrength.Thus,ductile exuralfailurewasthedominantmodeoffailure.TheotherRCbeamsweredesignedtobede cientinshearcapacity;thus,shearfailurewastheirdomin …… 此处隐藏：5712字，全部文档内容请下载后查看。喜欢就下载吧 ……