NATO SfPNATO SfP--977231 977231 ClosingClosing WorkshopWorkshop

IN SERVICE SEISMIC IN SERVICE SEISMIC STRENGTHENING OF RC STRENGTHENING OF RC FRAMED BUILDINGSFRAMED BUILDINGS

Tankut/Ersoy/Ozcebe/Baran/OkuyucuTankut/Ersoy/Ozcebe/Baran/OkuyucuMiddleMiddle East East TechnicalTechnical UniversityUniversity

Ankara, TurkeyAnkara, Turkey

ACKNOWLEDGEMENTACKNOWLEDGEMENT

** A A productiveproductive researchresearch projectproject ..

-- Jointly funded byJointly funded by.. •• NATONATO •• TUBITAK TUBITAK ..

-- JointlyJointly realisedrealised byby.. •• TurkishTurkish •• GreekGreek.. •• MacedonianMacedonian •• AmericanAmerican ..

researchersresearchers......

** Not a Not a veryvery modestmodest presentationpresentation......

INTRODUCTIONINTRODUCTION

Reinforced concrete framed structure Reinforced concrete framed structure with hollow brick masonry infill with hollow brick masonry infill is the is the mostmost commoncommon systemsystem in in buildingsbuildings..

** LowLow--rise (1rise (1∼∼2 floor)2 floor) are not vulnerable;are not vulnerable;

* * HighHigh--rise (> 10rise (> 10∼∼12 floor)12 floor) buildings arebuildings are.. carefully designed and constructed;carefully designed and constructed;

** MidMid--rise (3rise (3∼∼8floor)8floor) bldgsbldgs of inferiorof inferior.. material, design and constructionmaterial, design and construction.. quality present the major problem.quality present the major problem.

INTRODUCTIONINTRODUCTION

MidMid--rise buildings of inferior qualityrise buildings of inferior quality

** Constitute the Constitute the majoritymajority everywhereeverywhere;;

** Collapse in the Collapse in the pancake modepancake mode; thus; thus

** Are responsible from the high number Are responsible from the high number of of human losses and severe damagehuman losses and severe damage,,

** Are generally toAre generally tooo good for demolition;good for demolition;

** Are greatly in Are greatly in need of rehabilitationneed of rehabilitation..

INTRODUCTIONINTRODUCTION

Common deficiencies of such buildings:Common deficiencies of such buildings:

** Insufficient lateral stiffnessInsufficient lateral stiffness

** Deficient reinforcement detailingDeficient reinforcement detailing-- Insufficient confinement & anchorageInsufficient confinement & anchorage-- Inadequate joint reinforcement etc.Inadequate joint reinforcement etc.

** Deficient design practiceDeficient design practice-- Horizontal/vertical irregularitiesHorizontal/vertical irregularities-- Short columns; soft storeys etc.Short columns; soft storeys etc.

** Poor concrete; poor workmanshipPoor concrete; poor workmanship etc.etc.

INTRODUCTIONINTRODUCTION

ClassificationClassification of of rehabrehab techniquestechniques::

** Member strengtheningMember strengthening((TTo io improvemprove theirtheir seismicseismic performanceperformance))-- Columns Columns ((N & MN & M)) -- Beams Beams ((M & VM & V))-- JointsJoints ((V ?V ?)) -- Slabs Slabs ((diaphdiaph actionaction))

** SystemSystem behaviourbehaviour imrovementimrovement((ToTo relieverelieve membersmembers fromfrom seismic seismic effectseffects))

-- LateralLateral stiffnessstiffness increasingincreasing elementselements

INTRODUCTIONINTRODUCTION

RehabilitationRehabilitation strategystrategy::

ConsideringConsidering the common deficiencies, the common deficiencies, the the mostmost sensiblesensible approachapproach isis

** System behaviourSystem behaviour improvementimprovement.. complementedcomplemented byby

** StrengtheningStrengthening of a limited numberof a limited number.. ofof deficient membersdeficient members

THE BASIC QUESTIONTHE BASIC QUESTION

** CastCast--inin--place place reifreif concconc infilled frame infilled frame technique is technique is suitable for postsuitable for post--quake quake repairrepair of the evacuated buildings; but of the evacuated buildings; but not for prenot for pre--quake rehabilitationquake rehabilitation of the of the buildings still in use.buildings still in use.

** Suitable techniques should be developed.Suitable techniques should be developed.

THE CHALLENGETHE CHALLENGE

To develop a rehabilitation method,To develop a rehabilitation method,

** Suitable for the common local building Suitable for the common local building type (Hollow brick infilled RC frame)type (Hollow brick infilled RC frame)

** Practical & economical, and above allPractical & economical, and above all

** Occupant friendly Occupant friendly ((no more disturbance no more disturbance than an ordinary painting job)than an ordinary painting job)

THE IDEATHE IDEA

** CastCast--inin--place reinforced concrete place reinforced concrete infill is known to improve the seismic infill is known to improve the seismic structural performance.structural performance.

** Why shouldnWhy shouldn’’tt the the existingexisting infillinfill wallwalldo the samedo the same, , ifif it is it is reinforcedreinforced withwith

-- HighHigh strstr precast precast concreteconcrete panelspanels oror

-- CFRP CFRP diagonalsdiagonals epoxyepoxy anchoredanchored totothe the wallwall andand the the frameframe membersmembers ??

THE ANSWERTHE ANSWER

The answer is The answer is OFROFR (occupant friendly rehab)(occupant friendly rehab)

** To reinforce existing masonry infill wall To reinforce existing masonry infill wall with epoxy bonded PC panels, which are,with epoxy bonded PC panels, which are,

-- Light enough to be handled by twoLight enough to be handled by two

-- Relatively thin, ~Relatively thin, ~440 mm (high 0 mm (high strstr))

-- Connected to infill wall by epoxy, andConnected to infill wall by epoxy, and.. to frame by epoxy bonded dowelsto frame by epoxy bonded dowels

TEST FRAMESTEST FRAMES

** ~~1/3 scale, one1/3 scale, one--bay, twobay, two--storey storey inferior quality RC frames,inferior quality RC frames,

(representing the actual practice)(representing the actual practice)

-- Strong beamStrong beam--weak columnweak column

-- Insufficient confinementInsufficient confinement

-- Low quality concrete (C13~C16)Low quality concrete (C13~C16)

PRECAST CONCRETE PANELSPRECAST CONCRETE PANELS

** ~1/3 ~1/3 scalescale, ~2.2 kg (~60 kg , ~2.2 kg (~60 kg prototypeprototype))

** TypesTypes A,C,EA,C,E: : nearlynearly squaresquare, , threethree layerslayers

** TypesTypes B,D,FB,D,F: : wallwall heightheight stripstrip

** EpoxyEpoxy mortarmortar betweenbetween panelspanels((InIn typestypes A & B, A & B, shearshear keyskeys on on allall sidessides andandweldedwelded connectionsconnections at at cornerscorners))

** EpoxyEpoxy mortarmortar betweenbetween wallwall & & panelspanels

PARAMETERS STUDIEDPARAMETERS STUDIED** Panel Panel geometrygeometry –– SquareSquare//stripstrip panelspanels

** Panel Panel connconn –– ShearShear keykey//weldingwelding//epoxyepoxy

** Panel Panel locationlocation –– IntInt/ / extext applicationsapplications

** DowelDowel sidessides –– FourFour//twotwo//oneone//nonenone

** FrameFrame floorsfloors –– TwoTwo//oneone floorfloor framesframes

** AspectAspect ratioratio –– StdStd//widewide//narrownarrow baysbays

** ColumnColumn steelsteel –– ContCont//lappedlapped steelsteel

** AxialAxial loadload –– 20 % / 10% of 20 % / 10% of axialaxial capcap

** Panel Panel concreteconcrete –– Normal Normal wtwt//lightlight wtwt

** Panel Panel reinfreinf –– Nominal Nominal gridgrid/ / fibrefibre reifreif

LOADING SYSTEMLOADING SYSTEM

Cross Beam

Prestressing

Cable

Universal Base

Foundation Beam

Load Cell

Ram

Pins

RamStrong Wall

Spreader Beams

RREFERENCEEFERENCE

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REFERENCEREFERENCE

STRENGTHENED (SQUARE)STRENGTHENED (SQUARE)

STRENGTHENED (STRIP)STRENGTHENED (STRIP)

ENVELOPE CURVESENVELOPE CURVES

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CR CIA

CIB CIC

CID CIC3

CIC4 CEE1

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CEER LR

LIC LID

ENERGY DISSIPATIONENERGY DISSIPATION

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0 2 4 6 8 10 12 14 16 18 20Cycle

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STIFFNESS DEGRADATIONSTIFFNESS DEGRADATION

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TEST RESULTSTEST RESULTS

** SameSame seisseis capcap improvementimprovement as as castcast--inin--situsituRC RC infillinfill, , slightlyslightly smallersmaller ductilityductility..

** No No needneed forfor shearshear keyskeys andand weldingwelding..

** No No diffdiff betweenbetween squaresquare//stripstrip panelspanels..

** EquallyEqually effectiveeffective intint//extext applicationsapplications..

** DowelsDowels on on fourfour sidessides in in criticalcritical 22∼∼3 3 floorsfloors; ; reducedreduced dowelsdowels ((eveneven nonenone)) in in upperupper floorsfloors..

** SimilarSimilar resultsresults fromfrom oneone//twotwo floorfloor framesframes..

** SimilarSimilar resultsresults forfor diffdiff aspectaspect ratiosratios (?)(?)

PERFORMANCE IMPROVEMENTPERFORMANCE IMPROVEMENT

RelativeRelative toto masonrymasonry RelativeRelative totoinfilled infilled frameframe barebare frameframe

LateralLateral loadload capacitycapacity ∼∼2.5 2.5 timestimes ∼∼ 15 15 timestimes

LateralLateral stiffnessstiffness ∼∼ 3 3 timestimes ∼∼ 20 20 timestimes

DuctilityDuctility ∼∼ 2 2 timestimes ∼∼ 0.2 0.2 timestimes

EnergyEnergy dissipationdissipation ∼∼ 3 3 timestimes ∼∼ 60 60 timestimes

INTERPRETATIONINTERPRETATION

Significantly improved performance:Significantly improved performance:

** Increased load carrying capacityIncreased load carrying capacity

** Increased initial & final stiffnessIncreased initial & final stiffness

** Delayed strength degradationDelayed strength degradation

** Decelerated stiffness degradationDecelerated stiffness degradation

** Better ductilityBetter ductility

** Much higher energy dissipationMuch higher energy dissipation

SHAKE TABLE TESTSSHAKE TABLE TESTS

Very satisfactory seismic performanceVery satisfactory seismic performance** Five Five IzmitIzmit earthquakes (magnified)earthquakes (magnified)** Intact shear wallIntact shear wall** Expected cracking in coupling beamsExpected cracking in coupling beams** Reasonable Reasonable stiffnessstiffnesss degradations degradation

Lap splice failure and its repairLap splice failure and its repair** Two more Two more IzmitIzmit earthquakesearthquakes** Much better performanceMuch better performance

Worst possible punishmentWorst possible punishment** Still very satisfactoryStill very satisfactory

PROPOSALS FOR DESIGNPROPOSALS FOR DESIGN

** ProposedProposed methodsmethods of of analysisanalysis on the on the basisbasisof of analyticalanalytical evaluationevaluation of test of test resultsresults::

-- ShearShear wallwall withwith ““equivalentequivalent thicknessthickness””.. reflectingreflecting ((brickbrick+ plaster+ + plaster+ epoxyepoxy+ panel) + panel) .. contributioncontribution ((alreadyalready in in useuse forfor RC RC infillinfill))

-- DoubleDouble diagonaldiagonal strutstrut withwith ““equivalentequivalent.. widthwidth”” reflectingreflecting the the samesame ((modmod SmithSmith))

** LastLast touchestouches areare in in progressprogress......

CONCLUSIONCONCLUSION

PC panel technique is a very effective PC panel technique is a very effective and practical seismic rehabilitation and practical seismic rehabilitation method for existing buildings.method for existing buildings.

** Leads to a significant improvement in Leads to a significant improvement in seismic performanceseismic performance

** Is easily applied to buildings in use Is easily applied to buildings in use with minimal disturbancewith minimal disturbance

** Is cost effective Is cost effective (C(Constructiononstruction costcostcomparablecomparable to castto cast--inin--place RC infills)place RC infills)

IMPLEMENTATIONIMPLEMENTATION

A A recentlyrecently submittedsubmitted FP6 FP6 projectproject of of €€ 5M5M

** AimsAims at the at the implementationimplementation of of newnew seismic seismic rehabilitationrehabilitation techniquestechniques throughthrough SMESME’’ss;;

** InvolvesInvolves SMESME’’ss of of GermanyGermany, , GreeceGreece, , ItalyItaly, , MacedoniaMacedonia andand PortugalPortugal besidesbesides Turkey;Turkey;

** IncludesIncludes 10 10 workwork packagespackages of of whichwhich 6 6 arearerelatedrelated ((2 2 directlydirectly, 4 , 4 indirectlyindirectly)) toto OFR;OFR;

** InvolvesInvolves researchresearch, , trainingtraining, , disseminationdisseminationandand model model applicationsapplications..

THANKSTHANKS

forfor youryour patiencepatience

andand attentionattention......

NATO SfPNATO SfP--977231 977231 ClosingClosing WorkshopWorkshop

IN SERVICE SEISMIC IN SERVICE SEISMIC STRENGTHENING OF RC STRENGTHENING OF RC FRAMED BUILDINGSFRAMED BUILDINGS

Tankut/Ersoy/Ozcebe/Baran/OkuyucuTankut/Ersoy/Ozcebe/Baran/OkuyucuMiddleMiddle East East TechnicalTechnical UniversityUniversity

Ankara, TurkeyAnkara, Turkey