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Analysis of Analysis of InfilledInfilled ReinforcedReinforced
Concrete Frames Strengthened Concrete Frames Strengthened
with Fwith Fiberiber RReinforcedeinforced PPolymerolymerss
BarBarışış BiniciBinici
GGüüney ney ÖÖzcebezcebe
MiddleMiddle East East TechnicalTechnical UniversityUniversity
DepartmentDepartment of of CivilCivil EngineeringEngineering
ContentsContents
•• FRP FRP retrofitretrofit schemescheme
•• BehaviorBehavior andand failurefailure modesmodes
•• AnalyticalAnalytical modelingmodeling
•• ExperimentalExperimental verificationverification
•• CaseCase studystudy
•• ConclusionsConclusions
• Large building stock requiring upgrades
• Common method: Addition of shear walls
• Alternatives are needed
(rapid, economical, less disturbance)
• Significant amount of infill walls
- Not accounted in the design
- Susceptible to out of plane failure
FRP FRP RetrofitRetrofit of of InfillInfill WallsWalls
FRP FRP DowelsDowels
FRP FRP AnchorsAnchors
UnidirectionalUnidirectional
FRP FRP SheetSheet
PlasteredPlastered infillinfill wallwall
DisadvantagesDisadvantages: :
--MaterialMaterial CostCost
--RequiresRequires infillinfill wallswalls
AdvantagesAdvantages: :
-- RapidRapid retrofitretrofit
-- LittleLittle disturbancedisturbance
HowHow toto analyzeanalyze (NSP) (NSP)
andand designdesign FRPs in FRPs in
buildingbuilding retrofitretrofit??
1a1a
1b1b
LoadingLoading directiondirection
2a2a2b2b
ModeMode 1:1:
a)a) FRP FRP anchoranchor pulloutpullout
b)b) CornerCorner crushingcrushing (CC)(CC)
ModeMode 2:2:
a)a) FRP debondingFRP debonding
b)b) SlidingSliding /CC/CC
1a2b
FiniteFinite Element Element AnalysesAnalyses
AnchoredAnchored
regionregion
FrameFrame
seperationseperation
DeformedDeformed ShapeShape PrincipalPrincipal StressesStresses
AnalyticalAnalytical Model (STM) Model (STM)
FRP FRP tietie
InfillInfill strutstrut
PlasticPlastic hingehinge
element element withwith fiber fiber
discretizationdiscretization
elasticelastic frameframe
elementselements
OPENSEES Platform
FRP FRP TiesTies
cracking
wf
StressStress
StrainStrain
crtf
utf
efff ,εcrtε
tuε
tieftie twA =
inpftie tttt ++=
tie
crt
crtA
Vf =
tie
ffeffff
utA
twEf
,ε=
MeasuredMeasured
εεf,f,effeff ::
-- AnchorAnchor failurefailure: 0.002: 0.002-- 0.0030.003
--Debonding : 0.004 Debonding : 0.004 -- 0.0060.006εεtutu ≈≈ 3 3
εεf,f,effeff
InfillInfill StrutsStruts((SaneinejadSaneinejad and Hobbsand Hobbs 1995, 1995, ElEl--DakhakhiDakhakhi et. al. et. al. 2003)2003)
StressStress
StrainStrain
usf
soε fsεcrsε
smE
Incorporates:
-Frame-infill contact length
- Relative flexibility of members
- Presence of plaster
st
us
usA
Vf = ( )ccssus VVV ,min=
stsst twA =st
pminin
smt
tEtEE
+=
=FRPwith
FRPno
efff
crs
so
,2ε
εε
=202.0
1/01.0
Mode
ModeFRPnofsε
ExperimentalExperimental VerificationVerification
• Studies: Akgüzel (2000), Erduran (2002), Erdem (2003)
• Typical details of construction
- Plain bars
- Insufficient stirrup spacing
- Lap splices
- Low concrete strength (10 - 15 MPa)
- Infills with plaster (fcm ≈ 2MPa , fcp ≈ 4MPa)
• Carbon fiber reinforced polymers (fCFRP =3450 MPa)
-150
-100
-50
0
50
100
150
-60 -40 -20 0 20 40 60
Roof Dispalcement (mm)
Ap
pli
ed
Lo
ad
(kN
)
Akgüzel (2000)
ColumnsColumns DetailsDetails: :
100 mm x 150 mm 100 mm x 150 mm
ρρ == 1. 3 % 1. 3 %
N/NN/Noo ≈≈ 0.10.1
s = 95 mms = 95 mm
15
0
mm
100
mm 4Ф8
Bare frame
Frame with infills
FRP (Mode 1)
FRP (Mode 2)
2F
F
750 mm
750 mm
1300 mm
200 mm
200 mm
-80
-60
-40
-20
0
20
40
60
80
-50 -40 -30 -20 -10 0 10 20 30 40 50
Roof Displacement (mm)
Ap
pli
ed
Lo
ad
(kN
)
Erdem (2003)
ColumnsColumns DetailsDetails: :
110 mm x 110 mm 110 mm x 110 mm
ρρ == 1. 6 % 1. 6 %
N/NN/Noo ≈≈ 0.10.1
s = 100 mms = 100 mm
11
0 m
m
110
mm 4Ф8
Bare frame
Frame with infills
FRP (Mode 1)
1490 mm 890 mm 1490 mm
85
0 m
m1
42
5 m
m
400 mm
200 mm
-120
-70
-20
30
80
130
-25 -15 -5 5 15
Roof displacement (mm)
Ap
pli
ed
Lo
ad
(kN
)
Erduran (2002)
ColumnsColumns DetailsDetails: :
100 mm x 150 mm 100 mm x 150 mm
ρρ == 1. 3 % 1. 3 %
N/NN/Noo ≈≈ 0.250.25
s = 90 mms = 90 mm
15
0
mm
100
mm 4Ф8
Bare frame
Frame with infills
FRP (Mode 1)
750 mm
750 mm
1300 mm
200 mm
200 mm
AssumedAssumed deformationdeformation ofof a a wallwall
andand FRP FRP strainstrain
h
θθθθ
δL
δδcoscos θθ
h / sin
h / sin θθ
Evaluation of Evaluation of DeformationsDeformations
θθ
εδ
sincos
,efff
hDR ==
0
0.5
1
1.5
2
30 45 60θ (degrees)
Dri
ft R
atio (%
)
0.002
0.003
0.004
0.005
0.006
IDR max ≈ 2 εf,eff
CaseCase StudyStudyAnalyzed frameAnalyzed frame
4 @
5 m
4@ 4 m
5 @
3 m
Columns: 400 mm x 400 mm , Columns: 400 mm x 400 mm , ρρ = 1%= 1% , s = 350 mm, s = 350 mm
Beams : 300 mm x 600 mm , Beams : 300 mm x 600 mm , ρρ = = 0.5%0.5%
ffcc' = 10 MPa , ' = 10 MPa , ffyy = 420 MPa, = 420 MPa,
ffmcmc = 2 MPa, t= 2 MPa, tinin = 100 mm = 100 mm
ffcpcp = 2 MPa, = 2 MPa, ttpp = 40 mm= 40 mm
ffCFRPCFRP = 3450 MPa, = 3450 MPa, wwff =750 mm (similar to compression strut width !)=750 mm (similar to compression strut width !)
0
0.04
0.08
0.12
0.16
0.2
0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 1.2% 1.4%
Roof Displacement/Building Height
Ba
se
Sh
ea
r/B
uil
din
g W
eig
ht FRP Retrofit
Bare Frame
Frame with Infills
• Limited ductility gain
• Strength increase (50 %)
Concluding RemarksConcluding Remarks
• A simple model is proposed for FRP retrofitted infilled RC frames.
• Comparisons of model estimations and experiments are in agreement.
• Strength increases with limited ductility can be achieved with the proposed retrofit scheme.
Check :
- FRP anchor design
-Significant uplift rotations due to splice deficiencies
(welding of splices for plain bars !)
- Foundation capacity