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