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
-200
-150
-100
-50
0
50
100
150
200
-50 -40 -30 -20 -10 0 10 20 30 40 50
a. Test PR
Lat
eral
Load
(k
N)
Top displacement (mm)
STRENGTHENED (SQUARE)STRENGTHENED (SQUARE)
-200
-150
-100
-50
0
50
100
150
200
-50 -40 -30 -20 -10 0 10 20 30 40 50
b. Test PI1
Lat
eral
Load
(k
N)
Top displacement (mm)
STRENGTHENED (STRIP)STRENGTHENED (STRIP)
-200
-150
-100
-50
0
50
100
150
200
-50 -40 -30 -20 -10 0 10 20 30 40 50
c. Test PI2
Lat
eral
Load
(k
N)
Top displacement
REFERENCEREFERENCE
STRENGTHENED (SQUARE)STRENGTHENED (SQUARE)
STRENGTHENED (STRIP)STRENGTHENED (STRIP)
ENVELOPE CURVESENVELOPE CURVES
-250
-200
-150
-100
-50
0
50
100
150
200
250
-50 -40 -30 -20 -10 0 10 20 30 40 50
Top Displacement (mm)
La
tera
l L
oa
d (
kN
)
CR CIA
CIB CIC
CID CIC3
CIC4 CEE1
CEF CEE
CEER LR
LIC LID
ENERGY DISSIPATIONENERGY DISSIPATION
0
5
10
15
20
25
0 2 4 6 8 10 12 14 16 18 20Cycle
Cu
mu
lati
ve
Dis
sip
ate
d E
ner
gy
(k
N.m
)
CIA
CIB
CIC
CID
CIC3
CIC4
CR
CEE1
CEF
CEE
CEER
LR
LIC
LID
STIFFNESS DEGRADATIONSTIFFNESS DEGRADATION
0
20
40
60
80
100
120
140
160
1 3 5 7 9 11 13 15 17 19 21
Cycle
Sti
ffn
ess
Deg
rad
ati
on
In
dic
ato
r (k
N/m
m)
CR
CIA
CIB
CIC
CID
CIC3
CIC4
CEE1
CEF
CEE
CEER
LIC
LID
LR
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