Improving shear capacity of existing RC beams using external(4)

Allsteelmembertypesbondedexternallyhadimprovedbeamstrength,stiffnessandductility.

Strengthenedspecimensshowedsimilarbehaviortoacontrolspecimenupto exuralyield.Specimensreachedthe exuralyieldstrengthwiththesamestiffnessfornearlythesameloadanddisplacement.

Thetypeofsteelmemberanditsarrangementonthebeamwereamongtheeffectiveparametersdirectingtheductilitybehavioranddeterminingthefailuremode.Thedisplacementductilityratiowasincreasedwhenthespacingofthesteelstrapswasdecreased.Increaseinthebondingareaontheshearspanreducedthepropagationofshearcrackssigni cantly.Specimensthatwerestrengthenedwith“L”typesteelstrapshadthelowestductilityratioamongthespecimens.

Specimensthatwerestrengthenedwithsteelplatesshowedstrengthandductilityclosetothoseofthecontrolmember.Steelplatespreventedpropagationofshearcracks,clearly.Insteadofusingonelargesteelplatealongthewholeoftheshearspan,segmentingthesteelplatesandthenbondingthemadjacenttoeachothertothebeam’sshearspanshowedsuccessfulresults.

Thefollowingcanbesuggestedforfutureworkonthissubject:thestrengtheningtechniqueshouldbeinvestigatedundercyclicreversalloads;thebehaviorsofthespecimensshouldberesearchedunderlongtermloads;andanalyticalmethodsforcalculatingshearcapacitiesofstrengthenedbeamsshouldbeimproved.

Conversionfactors1mm=0.039in.1mm2=0.00152in.21kN=0.2248kips1MPa=145psi

Symbolsa:Shearspan

d:Effectiveheightofthecrosssectionfc:Compressionstrengthofconcretefsy:Yieldstrengthofreinforcement

fspy:YieldstrengthofsteelstrapsandplateshS,hW:Steelstrapheight,steelplateheightL:Restraintspanofbeam

Mcal.:CalculatedmomentcapacitiesofspecimensMexp.:ExperimentalmomentcapacitiesofspecimensMU:SpecimenmomentcapacitiesVC:ShearforcecarriedbyconcreteVU:Shearcapacitiesofspecimens

VS:ShearforcecarriedbyshearreinforcementsVP:ShearforcecarriedbysteelstrapsorplatesSp:

Steelstrapspacing

粘钢加固钢筋混凝土梁斜截面

S.Altinetal./EngineeringStructures27(2005)781–791791

ts:

SteelstrapwidthδDisplacements

ε1,...,δ11:CU:Maximumstrainofconcreteφρ:Diameterofreinforcementsw:

Ratioofshearreinforcements

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