RetrofittingEarthquake-DamagedRCStructuralWallswithOpeningsbyExternallyBondedFRPStripsandSheetsBingLi1;KaiQian,A.M.ASCE2;andCaoThanhNgocTran3Abstract:Themajorityofresearchstudiesonthebehaviorofreinforcedconcretememberswithexternallybondedfiberreinforcedpolymer(FRP)sheetshavebeenfocusedonbeams,columns,andbeam-columnjoints.However,limitedexperimentalstudieshavebeenconductedtoinvestigatetheperformanceofstructuralwallsretrofittedbywrappingFRPstripsorsheets,especiallyonstructuralwallswithopenings.Thevalidatedretrofittingschemesforstrengtheningdamagedwallswithoutopeningsmaynotbesuitableforwallswithopenings.Therefore,aseriesofexperimentalstudieswerecarriedoutatNanyangTechnologicalUniversity,Singapore,tostudytheeffectivenessoftheproposedrepairandstrengtheningschemesinrecoveringtheseismicperformanceofthedamagedwallswithirregularorregularlydistributedopenings.Thestrut-and-tieapproachwasutilizedtodesigntherepairschemes.Therepairedwallsmanagedtorecovertheirstrength,dissipatedenergy,andstiffnessreasonably,indicatingthatthestrut-and-tieapproachcanbeagooddesigntoolforFRP-strengtheningofstructuralwallswithopenings.Moreover,theshearandslidingcapacitiesofrepairedwallswereenhancedbyusingfiberanchors.Therepairedwallsfailedprimarilybecauseofdebondingofthefiberreinforcedpolymeratthebaseofthewalls.DOI:10.1061/(ASCE)CC.1943-5614.0000336.©2013AmericanSocietyofCivilEngineers.CEDatabasesubjectheadings:Earthquakes;Seismiceffects;Fiberreinforcedpolymer;Walls;Openings;Bonding;Rehabilitation.Authorkeywords:Repair;Fiberreinforcedpolymers;Wall;Opening;Strut-and-tie;Reinforcedconcrete.IntroductionRCstructuralwallsplayaveryimportantroleincarryinglateralloadingandresistingdriftintallbuildings.Piercingawallwithopeningsmaysignificantlyinfluenceitsbehaviors,suchaschang-ingitsforcetransfermechanism,deductingitsstrengthandstiffness,anddecreasingitsductilitylevel.Althoughwallswithopeningshavebeenstudiedbysomeresearchers(Yanezetal.1992;AliandWight1991;Marti1985),theeffectsoftheregularandirregularopeningsontheseismicperformanceofRCwallsarestillnotfullyunderstood.Thus,two3-storyreinforcedconcretemodelwalls,scaledtoone-third,weretestedunderreversedcycliclateralload.SspecimensW1andW2weredesignedwithsimilardimensionsanddetailsasYanezetal.(1992)andMarti(1985),respectively.Moreover,fordetailedresultsofthesetwocontrolspecimensrefertoWu(2005)andZhao(2004),respectively.Thegoalofthispaperistoinvestigatewhetherthedamagedwallswithopeningscouldrestoretheirseismicperformancesafterproposedretrofitting.Fiberreinforcedpolymers(FRP)wereutilizedinthisstudybecauseoftheirhighstrength-to-weightratios,corrosionresistance,easeofapplication,andtailorability.Inaddition,theorientationofthefiberineachplycanbeadjustedtomeetspecificstrengtheningobjectives(Engindenizetal.2005).Althoughnumerousresearchstudieshadbeenconductedtostrengthenorrepairthestructuralcomponents,suchasbeams,col-umns,andbeam-columnjoints(LamandTeng2001;TengandLam2002;Pampaninetal.2007;Tengetal.2009;LiandChua2009;LiandKai2011;El-MaaddawyandChekfeh2012),therearelimitedexperimentalstudiesthatwereconductedtoinvestigatetheeffectivenessofFRPretrofittingthedamagedRCstructuralwalls,especiallyforwallswithopenings.Nealeetal.(1997)havetestedwall-likecolumnsthatwerestrengthenedusingFRP,includingwall-likecolumnswithdifferentarrangementsofexternallybondedFRPreinforcementssubjectedtouniaxialcompressiononly.Lombardetal.(2000)performedrehabilitationofstructuralwallsusingcarbonfiberreinforcedpolymer(CFRP)externallybondedtothetwofacesofthewalltoincreaseitsflexuralstrength.Theuseofunidirectionalcarbonfi-berswiththefibersalignedintheverticaldirectionincreasedtheflexuralcapacityandprecrackedstiffnessandthesecantstiffnessatyield.Severalnonductilefailuremodesofthewallwereattributedtothelossofanchorageortearingofthefibers.Antoniadesetal.(2003)testedsquatRCwallsuptofailureandthenrepairedthemusinghigh-strengthmortarandlap-weldingoffracturedreinforce-ment.ThewallsweresubsequentlystrengthenedbyexternallybondedFRPsheetsaswellasbyaddingFRPstripstothewalledges.FRPincreasedthestrengthoftherepairedwallsbyapprox-imately30%comparedwithtraditionallyrepairedwalls.However,theenergydissipationcapacityofthecontrolwallscouldnotberestoredcompletely.LiandLim(2010)retestedfourseismicallydamagedstructuralwalls(twolow-risewallsandtwomedium-risewalls)afterconventionallyrepairedandstrengthenedbywrappingwithFRPsheets.ItwasreportedthattherepairedandstrengthenedwallswereabletorestoretheperformanceofthedamagedRCwalls.Thisrepairmethodisrelativelyeasy.1AssociateProfessorandDirector,NaturalHazardsResearchCentreatNanyangTechnologicalUniv.,Singapore639798(correspondingauthor).E-mail:cbli@ntu.edu.sg2ResearchAssociate,NaturalHazardsResearchCentreatNanyangTechnologicalUniv.,Singapore.E-mail:qiankai@ntu.edu.sg3Lecturer,Dept.ofCivilEngineering,InternationalUniv.,VietnamNationalUniv.,HoChiMinhCity,Vietnam.E-mail:tctngoc@hcmiu.edu.vnNote.ThismanuscriptwassubmittedonFebruary24,2012;approvedonSeptember25,2012;publishedonlineonSeptember27,2012.Discus-sionperiodopenuntilSeptember1,2013;separatediscussionsmustbesubmittedforindividualpapers.ThispaperispartoftheJournalofCom-positesforConstruction,Vol.17,No.2,April1,2013.©ASCE,ISSN1090-0268/2013/2-259-270/$25.00.JOURNALOFCOMPOSITESFORCONSTRUCTION©ASCE/MARCH/APRIL2013/259J. Compos. Constr. 2013.17:259-270.
