=

NTTN=

SWrucWural Analysis of HisWorical ConsWrucWions – Jerzy Jasieńko (ed) © 2012 DPNH ProcławH PolandH ISSN 0860-2395H ISBN 978-83-7125-216-7

MAplkoY ClkcfkbMbkq tfqe pom ClMmlpfqbp Antonio BorriNI diulio CastoriOI Marco CorradiP ABpqoACq qhe= application= of= pteel= fiber= oeinforced= molymer= EpomF= as= a= means= of= increasing= the= capacity= of=masonry= columns= is= investigated= in= this= studyK= qhe= behavior= of= OP= solidJbrick= specimens= that= are=externally=wrapped=by=pom=sheets=in=low=volumetric=ratios=is=presentedK=qhe=specimens=are=subjected=to=axial=monotonic=load=until=failure=occursK=qwo=widely=used=types=of=masonry=columns=of=differing=square= crossJsections= were= tested= in= compression= Esquare= and= octagonal= crossJsectionsFK= lctagonal=crossJsection=masonry=columns=are=common=in=many=historical=constructions=and=no=data=are=present=in=bibliography=on=their= mechanical=behaviorK=qwo=different= configurations=of= the=reinforcing=system=were =investigatedW =pom =sheets =are =applied =as =external =reinforcement =along =the =perimeter =of =the =masonry=columns=in=the=form=of=continuous=and=discontinuous=wrapI=respectivelyK=qo=elaborateI=in=the=first= case= the= confinement= was= provided=by=a= continuous= laminateX= whereas= in= the= second= case= the=confinement=was=provided=by=three=pom=stripsI=NMM=mm=wide=and=OMM=mmK=ft=is=concluded=that=pomJconfined= masonry= behaves= very= much= like= fiber= reinforced= polymers= EcomFJconfined= masonryK=Confinement= increases= both= the= loadJcarrying= capacity= and= the= deformability= of= masonry= almost=linearly=with=average=confining=stressK= A=comparative=analysis=between=experimental=and= theoretical=values=computed=in=compliance=with=the=ftalian=Council=of=oesearch=ECkoF=was=also=developedK==heywords: Masonry columnI pteel fibresI oeinforcementI Confinement NK fkqolarCqflk =A= large=number= of= existing=masonry= structures= shows= damages= due= to= a= wide=range=of= events= EiKeKI=inadequate= construction= techniques= and= materialsI= foundation= settlementsI= seismic= loadsI= and=environmental= deteriorationFK= bven= when= these= structures= are= not= affected= by= strong= signals= of=deteriorationI= they=often=need=to=be=upgraded=to=meet=new=mandatory=seismic=design=requirements=or=to=allow=a=change=of=use=of=the=buildingK=qhus=seismic=retrofit=and=strengthening=of=masonry=structures=is=of=primary=importance=for=maintenance=of=the=ftalian=and=buropean=architectural=cultural=heritageK=qhis= was=verified=by= the=recent= earthquakes= that=produced=inestimable=damage= in=central= ftalyK=qhe=problem=of=masonry=elements=subjected=to=compressive=overloads=due=to=static=or=seismic=forces=is=of=primary= importance= in= order= to= avoid= sudden= brittle= failureK= qhe= solutions= adopted= should= restore=structural=safety=without=changing=the=architectural=valueI=the=shapeI=and=the=weight=of=the=elementsK=fn= the= last=decadesI= reinforced=concrete= xNz= or= steel= jacketing=were= largely=used= to= increase=both=axial=strength= and= deformation= capacity= of= masonry= columns= through= confinementK= qhese= wellJknown=techniques=have=proven=to=be=effectiveI=but=are=often=shortJlivedI=laborJintensiveI=and=usually=violate=the=aestheticI= conservation= and= restoration= requirementsK= joreover= the= mass= added= by= that= kind= of=intervention= could= generate= a= significant= extra= weight= inducing= an= increase= of= seismic= actions= to= be=computed= and= consequently= the= need= for= foundation= upgradeK= Consequently= to= overcome= these=limitationsI= the=interest=of=workers=in=this=field=has=become=increasingly=devoted=to=the=development=of=fiberJreinforced=polymer= EcomF=composites= in=the=form=of= epoxy=bonded=strips=or= jacketsK=As=found=in=literature=xOJRzI=confinement=of=masonry=columns=with=com=laminates=could=imply=significant=advantages=

================================================N=mrofessorI=Civil=and=bnvironmental=bngineering=aepartmentI=rniversity=of=merugiaI=merugiaI=ftalyX=O=oesearcherI=Civil=and=bnvironmental=bngineering=aepartmentI=rniversity=of=merugiaI=merugiaI=ftalyI=

gcastori]struttureKunipgKit=P=oesearcherI=Civil=and=bnvironmental=bngineering=aepartmentI=rniversity=of=merugiaI=merugiaI=ftalyI=

mcorradi]struttureKunipgKit=

=

NTTO=

if=compared=to=traditional=techniques=such=asW=negligible=increase=of=both=cross=sectional=dimensions=and=member= mass= as= well= as= a= faster= and=easier= installation=procedureK= eoweverI= later= studies= xSJVzI= have=shown=that=the=effectiveness=of=the=com=wraps=is=significantly=affected=by=the=corner=radius=of=columnsK=aue=to=the=low=shear=strength=of=com=materialsI=squareJ=and=rectangularJsection=masonry=columns=were=found= to= experience= less= increase= in= strength= and= deformation= capacityK= A= possibly= interesting=development= in= the=use= of= composites= regards= innovative= materialsI= based=on=ultra= high= strength= steel=filaments= xNMz=twisted=to=form=cords=and=embedded=in=either=an=epoxy=Ereferred=to=as=pteel=oeinforced=molymerI=pomF=or=mortar=Ereferred=to=as=pteel=oeinforced=droutI=podF=matrixK=fnherent=shear=strength=of=steel=cords=promotes=in=fact=effectiveness=of=reinforcementI=while=preventing=premature=material=failure=associated= with= sharp= cornersK= ln= the= other= handI= pom= and= pod= are= fairly= new= technologies= andI= at=presentI=few=studies=are=available=on=the=use=of=such=materials=as=strengthening=systems=xNNJNRzK==As= a= result= of= such=considerationsI= the=present=paper= aims= to=put= in= evidenceI= through=experimental=testsI= the= potential= of= masonry= confinement= by= using= steel= reinforced= compositesK= aifferent= crossJsection= geometry= EoctagonalI= square= and= rectangularF= as= well= as= different= amounts= and= different=schemes=of=confining=reinforcement=were=here=investigatedK=fn=particularI=two=different=strengthening=techniques= were= consideredI= namely= wrapping= with= continuous= or= discontinuous= pom= sheetsK= fn=additionI= experimental= results= were= used= to= assess= the= reliability= of= the= existing= design= equations=suggested=by=ftalian=kational=oesearch=Council=for=the=design=of=comJconfined=masonry=columnsK==OK abpCofmqflk lc qeb pqobkdqebkfkd qbCekfnrbp =

As= mentioned= aboveI= two= different= strengthening= schemes= were= consideredI= namely= wrapping= with=continuous= or= discontinuous= pom= sheetsK= fn= the= first= case= the= confinement= was= provided= by=a=continuous= laminate=composed= of= two=pom= strips=of= PMM= mm= width= each= EcigK=NaFX= whereas= in= the=second=case= the= confinement= was= provided=by= three= pom= stripsI= NMM=mm=wide=and=NNR=mm=spaced=EcigK=NbFK=fn=both=casesI=the=finishing=end=of=the=sheet=overlapped=the=starting=end=by=OMM=mm==

70

300

200

230

230

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530

aF=

100

100

200

100

100

530

115

115

bF=

cigK N Confinement=layout=Edimensions=in=mmFW=aF=continuous=wrappingX=bF=discontinuous=wrapping==

pom= strips= were= installed= following= the= recommendations= of= ACf= 44MKOoJMO= provisions= for= com=materialsK=qhe=masonry=surface=was=cleaned=with=abrasive=paper=to=remove=defects=and=possible=wet=partsK=tith=the=surface=roughened=and=cleanedI=a=first=layer=of=a=low=viscosity=epoxy=resin=was=used=on=the=surface=of=the=specimens=before=wrapping=with=the=pom=sheetsK=After=wrapping=a=second=layer=of=epoxy=resin=was=applied=and=a=roller=used=in=order=to=remove=any=air=voids=and=to=assure=an=effective=impregnation=of=the=resinK=As=the=surface=of=the=specimens=did=not=showed=any=significant=defectsI=the=application=of=a=epoxy=putty=was=not=considered=necessaryK==PK bumbofMbkqAi moldoAM

PKNK qest specimens A=total=of=OP=model=masonry=column=specimens=in=four=series=were=prepared=using=solid=clay=bricks=bonded=together=with=a=mortar=containing=cement=and=lime=as=binderI=at=a=waterWcementWlimeWsand=ratio=equal=to=MKVWNWPWTKR=by=weightK=qhe=crossJsectional=area=of=the=specimens=was=octagonal=Eside=average=dimension=equal=to=NMM=mmI=aspect=ratio=NWNF=in=the=first=series=and=ORM=×=ORM=mm=Easpect=ratio=NWNF=in=the=secondK=bach=specimen=was=RPM=mm=highI=corresponding=to=eight=courses=of=clay=bricks=with=seven=bed=joints=in=betweenI=as=shown=in=cigK=OK=qhe=thickness=of=the=mortar=bed=was=NO=mmI=and=the=corners=of =all =specimens=of =the=secondI =third=and=fourth=series =were=rounded=at =a =radius=of =OM=mm=to=reduce=any=detrimental=effect=of=the=sharp=corners=on=the=effectiveness=of=confinementK==

=

NTTP=

530

250

250

250

100

aF= ========

250

25053

0

250 bF=

cigK O ppecimens=details=Edimensions=in=mmFW=aF=first=seriesX=bF=second=series==

Another =test =variable =was =the =type =of =steel =cords =Eqype =N =or =OFK =lne =distinctive =feature =of =these =materials= is= their= macroscopic= structureK= All= the= fibers= are= made= up= of= highJstrength= steel= filaments=covered=with=a=layer=of=brass=to=prevent=oxidation=of=the=metallic=cordsK=qhese=cords=are=placed=side=by=side=and=glued=to=a=thin=polyester=mesh=to=allow=them=to=be=packaged= in=the=form=of=a=stripK=mlacing=these=metallic=cords=sideJbyJside=and=gluing=them=onto=thin=polyester=meshes=results=in=a=product=in=the=form=of=sheets=with=a=density=of=NO=cordsLinch=E4KTO=cordsLcmFI=which=are=then=wound=on=bobbinsK=qhe =qype =O =cord =is =made =by =twisting =five =individual =filaments =together =Ethree =straight =filaments =wrapped =by =two =filaments =at =a =high =twist =angleFK =qhe =qype =N =cord =results =from=winding =four =single =high= strength= metallic= filaments= togetherW= three= filaments= are= wound= together= by= a= single= external=filament= of= a= smaller= diameterK= qype= N= was= used= only= for= reinforcement= of= square= crossJsection=columnsI=and=qype=O=for=both=square=and=octagonal=crossJsections=columnsK=

=PKOK qest matrix lf=the=OP=samples= in=the=seriesI=NM=had=square=crossJsections=while= the=remaining=NP=had=octagonal=sectionsK= qhe= purpose= was= to= evaluate= the= increase= in= compressive= strength= of= masonry= columns=produced=by=the=reinforcement=wrapping=and=to=record=the=axial=stressJstrain=curveK=Another=important=objective=was=to=find=the=failure=mode=of=the=masonry=columnsK==aetails=about=the=model=columns= in=each=series=are=given=in=qabK=NK=qhe=specimens=are=identified=by=a=three= index= codeI= in= which= the= first= indicates= the= crossJsection= geometry= El= == lctagonalI= p= ==pquareFX=the=secondI=indicates=the=type=of=steel=cords=EPpu===qype=N=cordsX=PuO===qype=O=cordsFX=the=third=the=reinforcing=system=EC===Continuous=wrapX=a===aiscontinuous=wrapFK==

qable N=qest=matrix==

ppecimen phape of Cross-section

Matrix qype

oeinforcement qype

oeinforcing pcheme

N= octagonal= J= J= J=O= square= J= J= J=P= square= epoxy= qype=N= Continuous=wrap=4= square= epoxy= qype=N= Continuous=wrap=R= octagonal= epoxy= qype=O= Continuous=wrap=S= octagonal= epoxy= qype=O= aiscontinuous=wrap=T= octagonal= epoxy= qype=O= Continuous=wrap=U= octagonal= epoxy= qype=O= aiscontinuous=wrap=V= octagonal= epoxy= qype=N= Continuous=wrap=NM= octagonal= epoxy= qype=N= aiscontinuous=wrap=NN= octagonal= epoxy= qype=N= Continuous=wrap=NO= octagonal= epoxy= qype=O= aiscontinuous=wrap=NP= octagonal= epoxy= qype=N= aiscontinuous=wrap=N4= octagonal= epoxy= qype=N= Continuous=wrap=NR= octagonal= epoxy= qype=O= aiscontinuous=wrap=NS= octagonal= epoxy= qype=O= Continuous=wrap=NT= square= epoxy= qype=N= Continuous=wrap=NU= square= epoxy= qype=N= Continuous=wrap=NV= square= epoxy= qype=N= aiscontinuous=wrap=OM= square= epoxy= qype=N= aiscontinuous=wrap=ON= square= epoxy= qype=N= aiscontinuous=wrap=OO= square= epoxy= qype=N= aiscontinuous=wrap=OP= square= epoxy= qype=N= aiscontinuous=wrap=

=

NTT4=

PKPK Characterization of the materials qhe=mechanical=properties=of= the=solid=clay=bricks= EO4R=×=NOM=×=RR=mmF=used=for= masonry=column=construction=were=obtained=by=means=of=compression=and=bending=testsI=each=of=which=was=carried=out=on=six=samplesK=rniaxial=compression=tests=with=a=O4R=×=NOM=mm=crossJsection=gave=a=mean=strength=of=OMKVV=jmaI=whereas=the=mean=value=of=the=bending=tensile=strength=was=MKUN=jmaK==qhe= mortar= used= was= composed= of= mortland= cement= ENMB= in= volumeFI= sand= EUMB= in= volumeF= and=hydraulic= lime= ENMB= in= volumeFK= qhe= strength= of= the= mortar= was= determined= from= bending= and=compression=testingK=qhree=NSM=×=4M=×=4M=mm=prisms=were=tested=in=flexure=with=threeJpoint=bending=and=six=4M=×=4M=×=4M=mm=cubes=in=compressionK=qhe=OUJday=average=strength=results=were=as=followsW=PKRS=jma=for=flexion=tests=and=NMKTR=jma=for=those=of=compressionK=qensile= tests= were=performed=on=pom= laminates= to= determine= the= mechanical=properties= of= the=steel=cords=and=to=draw=their=stressJstrain=curvesK=qhe=mechanical=properties=of=the=metal=cords=were=verified=by= tensile= tests= carried= out= on= eight= samplesK= qests= were= executed= using= a= NMM= kk= displacementJcontrolled=universal=testing=machineK=pteel=fiber=behavior=turned=out=to=be=linearJelastic=up=to=failure=and=experienced=tensile=failureK=Average=tensile=strength=and=elastic=modulus=were=equal=respectively=to=PPNN=jma=and=ON4RSM=jma=for=qype=NI=and=ORNN=jma=and=NUTPRS=jma=for=qype=OK===PKQK qest setup qhe= tests= were= executed= in= loadJcontrol= mode=with= a= loading= rate=of= OLP= hkLs= using= a= compression=testing= machine= of= PMMM= kk= capacityK= qhe= purpose= was= to= evaluate= the= increase= in= compressive=strength= of= masonry= columns= produced= by= the= fiber= wrapping= and= to= record= the= axial= stressJstrain=curveK=Another=important=objective=was=to=find=the=failure=mode=of=the=masonry=columnsK=ioads=were=measured=using=a=load=cell=and=displacements=were=obtained=using=external=linear=variable=differential=transducers= EisaqsF= mounted= on= the= masonry= columns= Ebase= length= RMM= mmFK= ioads= and=displacements=were=all=recorded=by=a=data=acquisition=systemK===QK bumbofMbkqAi obpriqp

QKNK pquare Cross-pection masonry columns lne=of=the=ten=specimens=underwent= testing=without= any=type=of=reinforcementI= to=estimate=strength=and= stiffness= characteristicsI= while= the= remaining= nine= were= confined= with= two= different= types= of=reinforcing=system=Econtinuous=or=discontinuous=wrapF=embedded=in=an=epoxy=matrixK===

qable O pquare=crossJsection=masonry=columnsW=experimental=results==

peries ppecimen solumetric ratio (%)

meak load EkkF

meak strength EMmaF

ptrength increment

meak strain

rnconfined= O= –= TMU= NNKVN= NKMM= MKMMTM=pJPuOJC= PI=4I=NTI=NU= MKSM= NRNM= OSKSR= OKO4= MKMOOR=pJPuOJa= NVI=OMI=ONI=OOI=OP= MK4M= NNUV= NVKUU= NKST= MKMNTM==

qhe=control=specimen=failed=at=a= load=of=TMU=kkI=corresponding=to=a=compressive=strength=of=NNKVN=jma= EqabK= OFK=qhe= compression=stress= caused= the= columns= to= fracture=with=vertical= cracks= formed=through=mortar= joints=and=solid= clay=bricks=EcigK=PaFK=qhe=reinforcing=action=of= the=steel=cords=was=significant= for= both= the= reinforcing= schemesK= As= can= be= noted= in= qable= 4I= the=average= increase= in=strength= was= approximately= NO4B= in= the= case= of= continuous= wrap= Eperies= lJPuOJCF= and= STB= for=discontinuous=wrap=Eperies=lJPuOJaFK==All=strengthened=specimens=failed=by=the=rupture=of=the=pom=jacket=due=to=hoop=tension=after=the=masonry=had=disintegrated=EcigK=PbFK=qypical=failure=of=wrapped=specimens= was= very=noisy= followed=by=an=“explosive”= fracture=of= the= steel= cordsK=qhe= failure=was=preceded=by=a=visible=transversal=deformation=of=the=specimen=in=about=the=middleK=qhis=is=the=most=common= mode= of= failure= for= comJconfined= masonryI= although= premature= failure= due= to= the=separation= of= the= com= at= the= vertical= lap= joint= has= also= been= reported= for= specimens= with= an=insufficient=lap=lengthK=cigK=4=illustrates=a=comparison=between=the=stressJstrain=curves=obtained=from=the=experimental=tests=on=the= square= crossJsection= columnK= ft= can= be= observed= that= in= all= cases= the= columns= behaved= almost=linearly=until=they=reached=the=maximum=loadK=At=this=stageI=the=failure=mechanism=started=to=occur=and=a=sudden=drop=in=the=stressJstrain=curves=was=recordedK==

=

NTTR=

=aF=== =bF=cigK P cailure=modes=of=square=crossJsection=columnW=EaF=unreinforced=specimensX=EbF=reinforced=specimens=

=

aF= bF=cigK Q ptressJstrain=diagram=of=square=crossJsection=columnWaF=continuous=wrapX=bF=discontinuous=wrapK=

=QKOK lctagonal Cross-pection masonry columns qhirteen= octagonal= crossJsection= columns= were= tested= under= uniaxial= compression= until= failureK= qhe=control=specimen=failed=at=a=load=of=TNV=kkI=corresponding=to=a=compressive=strength=of=N4KM=jma=by=the=formation=of=vertical=cracks=through=the=head=joints=and=the=bricksK===

qable P lctagonal=crossJsection=masonry=columnsW=experimental=results==

peries ppecimen solumetric ratio (%)

meak load EkkF

meak strength EMmaF

ptrength increment

meak strain

rnconfined= N= J= TNV= N4KM= NKMM= MKMMUR=lJPpuJC= RI=TI=NS= MK4T= NPSN= OSKS= NKVM= MKMNSS=lJPpuJa= SI=UI=NOI=NR= MKPN= NOVP= ORKO= NKUM= MKMNOU=lJPuOJC= VI=NNI=N4= MKSO= NOUV= ORKO= NKTV= MKMNNT=lJPuOJa= NMINP= MK4N= NOO4= OPKV= NKTN= MKMNOT=

=qhe=most=important=experimental=result=for=the=thirteen=specimens=regards=the=increase=in=strength=and=deformation=capacity=attainable=in=a=column=confined=with= steel=cordsK=qhe=results= obtained=showed=a=significant=increase=in=strength=which=was=more=evident=in=the=case=of=Ppu=cordsK=As=can=be=noted=in=qabK=PI=the=average=increase=in=strength=was=approximately=VMB=in=the=case=of=continuous=wrap=Eperies=lJPpuJCF=and=UMB=for=discontinuous=wrap=Eperies=lJPpuJaFK=ConverselyI=the=columns=confined=with=PuO=cords=evidenced=an=average=increase=in=strength=of=TVB=and=TNB=for=peries=lJPuOJC=and=lJPuOJa=respectivelyK=tith= regard= to= the= failure=modeI= the=control= specimen= EcigK=RaF= developed=vertical=cracks=along= the=surfaces= for= an=initial=cracking=load=between=4OM=and=SMM=kkK=qhese=cracks= initiated= on=the=external=surface=of=the=masonry=column=and=then=spread=inwardsK=aespite=the=fact=that=material=properties=were=quite=similarI=the=specimen=with=octagonal=cross=section=was=strongerK=tith=regard=to=the=failure=mode=among=the=confined=columns=a=strong=resemblance= in= the=failure=mode=was=also=noted=EcigK=VbI=VcFW=during= the= initial= phase= of= the= compression= testsI= visible= deformations= were= not= encountered= in= all=twelve=reinforced=samplesW=increasing=the=load=vertical=cracks=formed=though=mortar= joints=and=bricks=and= a= progressive= transversal= dilation= of= the= masonry= columns= was= noted= which= terminated= in= the=failure=of=the=pom=materialK=At=the=end=of=the=testI=the=confined=portion=of=the=abovementioned=samples=turned= out= to= be= crushed= and= disintegratedI= and= in= any= case= more= damaged= compared= to= the= less=

=

NTTS=

confined= portions= adjacent= to= the= reinforcementI= which= broke= off= from= the= column= and= remained=attached= to= the= reinforcement= with=a= more= or= less= constant= thicknessK= cailure= of= the=sheet= occurred=midway=up=the=column=and=involved=an=area=covering=approximately=one=third=of=column=the=heightK===

=aF== =bF== =cF=

cigK R cailure=modes=of=octagonal=crossJsection=columnW=EaF=unreinforced=specimensX=EbF=reinforced=specimen=Econtinuous=wrapFX=EcF=reinforced=specimens=Ediscontinuous=wrapF=

=A=significant= increase=in=deformation=capacity=was=also=observed= in=all=cases=EcigK=SFK=qhe=postJpeak=behavior= in= the= majority= of= tests= was= marked= by= abrupt= loss= of= strength= over= a= very= narrow= strain=incrementI=accompanied=by=rupture=of=the=pom=jacketK===

aF= bF=cigK S ptressJstrain=diagram=of=octagonal=crossJsection=columnW=aF=continuous=wrapX=bF=discontinuous=wrap=

=RK abpfdk =qhe=equations= suggested=by= ftalian=Cko= xNSz= for=design=of=com= reinforcementI=based=on=buropean=Code= for= design= of= masonry= structures= xNTz= on= compressive= strength= testing= of= confined= masonry=columnsI= has= shown= that= the= design= compressive= strength= EfmcdF =for =members =confined =with =com =subjected=to=a=lateral=confining=pressure=Ef1F=can=be=written=as=followsW==

DD Nfkff mdmcd ×+= = ENF===where=fmd=represents=the=design=compressive=strength=of=unconfined=masonryI=k’=is=a=nonJdimensional=coefficient= and= f1’= is= the= effective= lateral= confing= pressureK= qhe= coefficient= k’= can= assume= different=valuesI =according =to =the =material =and =the =typology =of =the =applied =reinforcementK =cor =com =reinforcementI= the= value= of= k’= is= indicated= as= gmLNORM= where= gm= is= the= specific= weight= of= masonry=expressed=in=kgLmPK=qhe=effective=pressure=f1’=is=expressed=in=the=ptandard=asW==

NNN D fkkfkf seeff =×= == EOF===where= keff= is= the= effectiveness= coefficientK= qhis= value= is= the= product= between= two= termsW= ke= and= ks=related= to= the=horizontal= and= vertical= effectivenessK= qhe= effectiveness= coefficient= keff= depends= on= the=values= of= the=effectively=confined=volume= scIeff= to= the= total=volume= smK= qhe=horizontal=coefficient= kh=takes= into= consideration= the= percentage= of= confined= area= of= a= wrapped= sectionI= while= the= vertical=

=

NTTT=

effectiveness= coefficient=ks=covers= the=effect=of=discontinuous=wrapping=throughout= the=column=axisK=cor=the=square=cross=section=columnsI=the=horizontal=effectiveness=coefficient=is=equal=toW==

O OD DNPe

m

b dkA+

= - == EPF==

=where=b’=and=d’=are=indicated=in=cigK=Ta=and=Am=is=the=total=EgrossF=cross=sectional=areaK=

=

d

b

b'=b-2r

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qhe=authors=acknowledge=the=aepartment=of=Civil=mrotection=“Consorzio=oeirfp”=for=supporting=this=collaborative= researchK= qhanks= also= go= to= qecK= fnnK= pKrKlK= for= their= technical= assistance= during= the=strengthening=operations=and=cidia=pKrKlK=for=providing=the=steel=cordsK= obcbobkCbp xNz= hog=vK=CKI =lng=hK =CK =dKI =vuI =CK =eKI =preekanth=mK =sK =EOMMNF=oeinforced=concrete =jacketing=for =

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