Experimental and analytical investigation of seismic ...web/@eis/@research/...Experimental and analytical investigation of seismic performance of nonductile RC frames strengthened

Experimental and analytical investigation of seismic performance of nonductile RC frames strengthened with CFRP

Daiyu WangPh.D. Lecturer

Email: [email protected]

Date: 2015.12.07

Outline of the presentation

Research background

Axial stress-strain behavior of FRP-confined RC columns

Seismic performance of FRP strengthened RC members

Seismic performance of FRP strengthened RC frames

Research background

Nonductile frames: designed and built according to out-of-date codes, in which the earthquake loads are either not considered or not sufficiently considered. Insufficient ductility and energy dissipation capacity, deficient lateral load resistance,high risk level of severe damage or collapses in future strong earthquakes.

FRP (Fiber-Reinforced Polymer)

CFRP GFRP AFRP

Characters:High strength-to-weight ratioResistance to corrosion Ease of installation

Research background

Most existing research was focused on material and member level, few research was

conducted on the structural level.

Issues:

1. How to determine reasonable retrofit positions or members in a whole frame?

2. How to deploy the least amount of FRP for seismic retrofit requirement?

Research background

Constitutive relationship of FRP-confined concrete

(Material level)

Monotonic and cyclic axial compressive test of FRP-confined circular and square RC columns

Size effect on compressive behavior of FRP-confined square

concrete columns

Monotonic and cyclic axial stress-strain model of FRP-confined

concrete

Development of FRP-confined concrete material in OpenSees

Seismic performance of FRP strengthened columns and joints

(Member level)

Quasi-static test of FRP strengthened full-scale columns

Finite element analysis of FRP strengthened RC members

Hysteretic lateral load-displacement model of FRP

strengthened members


(structural level)

Shake table tests of nonductile RC frames strengthened with CFRP

wraps before earthquake

Finite element modeling of FRP strengthened RC frames

Analytical evaluation of seismic performance of FRP strengthened RC frames with different heights

Displacement-based seismic design method for FRP strengthened RC frames

Main research contents and objects

Quasi-static test of FRP strengthened full-scale beam-

column joints


Research background





Approximately 110 columns were conducted and tested under compressive, largest size 400×400mm

Larger circular (C1 series) Smaller circular (C2 series)

-0.02 -0.01 0.00 0.01 0.02 0.03

10

20

30

40

50

60

Lateral strain Axial strain

C1H1L1M C1H1L1C C1H1L0M

Axi

al st

ress

(MPa

)

-0 .02 -0.01 0.00 0.01 0.02 0.03

10

20

30

40

50

60

Lateral strain A xial strain

C2H 1L1M C2H 1L1C C2H 1L0M

Axi

al st

ress

(MPa

)


Test stress-strain results

-0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.050

10

20

30

40

50 S1H1L2C S1H1L2M S1H1L0M

Lateral strain Axial strain

Axi

al st

ress

(MPa

)

-0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.050

10

20

30

40

50 S2H2L0M S2H2L2C

S2H2L2M

Lateral strain Axial strian

Axi

al st

ress

(MPa

)

Larger square (S1 series) Smaller square (S2 series)

Have the same rc/b and same lateral effective confining pressure

200 mm

400 mm

2 layers of CFRP 4 layers of CFRP

2 f f fel

ntf

DE

εkfe fu

2D b

' ψ 3.3κcc f a lf f

2ea

c

2κ 1 (1 2 )3

cAA

rb

For square section:

Are the compressive strength of these two confined concrete columns should be the same ?

Noncircular cross section

ACI 440.2R-2008

Size Effect: Do small and large specimens have similar axial compressive behavior under the same lateral confinement ?



0.0 0.5 1.0 1.5 2.0 2.5 3.0

0.4

0.8

1.2

1.6

2.0N

orm

aliz

ed a

xial

stre

ss (

c/f c0)

Axial Strain c (%)

P100L1 P200L2 P300L3 P400L4

GA1

0.0 0.4 0.8 1.2 1.6 2.0

0.4

0.8

1.2

1.6

Nor

mal

ized

axi

al st

ress

(c/f c0

)

Axial strain c (%)

P175L1 P350L2

GA3

0.0 0.4 0.8 1.2 1.6 2.0

0.4

0.8

1.2

1.6

Nor

mal

ized

axi

al st

ress

(c/f c0

)

Axial strain c (%)

R175L1 R350L2

GB3

0.0

0.5

1.0

1.5

2.0

2.5

200L1175L2350L2175L1300L2300L3

Nor

mal

ized

ulti

mat

e st

ress

Size and FRP layers

unreinforced reinforced

200L2

0 1 2 3 4 50.2

0.3

0.4

0.5

0.6

0.7 This study Wang et al. (2011)

Effe

ctiv

e st

rain

fact

or

Normalized cross-sectional size B/100

=1-0.38(B/100)0.41

ε fufe 0.41

feε

fu

1 0.38100B

f f2 felf a

E ntf

D

2

e

c

2 21

31

cg

ga

g

B rAA

A



0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

10

20

30

40

50A

xial

Stre

ss (M

Pa)

Axial Strain

FRP-confined unreinforced concrete column FRP-confined reinforced concrete column

Axial stress and strain, shape of envelop and unloading/reloading stress-strain path, and plastic strain


0.000 0.004 0.008 0.012 0.016

10

20

30

40

50

60

70

CI-SC2

Test(Lam et al.) Model

Axi

al st

ress

c (M

Pa)

Axial strain c

0.000 0.004 0.008 0.012 0.016 0.020 0.024

10

20

30

40

50 Test Model

Axi

al st

ress

c (M

Pa)

Axial strain c

C1H1L1C

0.00 0.01 0.02 0.03 0.04

20

40

60

80 Test Model

Axi

al st

ress

c (M

Pa)

Axial strain c

C2H1L2C

0.000 0.005 0.010 0.015 0.020 0.025 0.030

20

40

60

80

100

CII-SC1

Test(Lam et al.) Model

Axi

al st

ress

c (M

Pa)

Axial strain c

Comparison between experimental and predicted stress-strain curves of FRP-confined circular columns


Comparison between experimental and predicted stress-strain curves of FRP-confined square columns

0.000 0.005 0.010 0.015 0.020 0.025 0.030

8

16

24

32

40 Test Model

Axi

al st

ress

c (M

Pa)

Axial strain c

S1H1L2C

0.000 0.005 0.010 0.015 0.020 0.025

5

10

15

20

25

30

35 Test Model

Axi

al st

ress

c (M

Pa)

Axial strain c

S2H0L1C

0.00 0.01 0.02 0.03 0.04 0.05

10

20

30

40

50

Axi

al st

ress

c (M

Pa)

Axial strain c

Test Model

S2H2L2C

0.000 0.005 0.010 0.015 0.020 0.025 0.030

9

18

27

36

45

Axi

al st

ress

c (M

Pa)

Axial strain c

Test Model

S2H2L1C


Research background





Quasi-static lateral load test of FRP strengthened full scale RC columns

Purpose: Investigate the influence of cross-sectional size and shape, axial compressive ratio,

layers of wrapped FRP on the seismic performance of FRP strengthened RC columns.

Specimen: 1. circular 3，D=400mm、3 layers of CFRP or GFRP、n=0.45；

2. square 10，B=300mm, 400mm、2, 3, 4 layers of CFRP，n=0.35, 0.45, 0.45.

Specimen dimensions and reinforcement details



Anchor bolts

MTS actuator

Reaction wall

specimen

LVDT

Steel hingeJack

Steel beam

Test setup and measurement system



Failure modes

C1H1C3N2C1H1L0N2 C1H1G3N2 S1H1C0N2 S1H2C0N2

S2H1C0N2 S1H1C3N2 S2H1C3N2 S2H1C2N1

Seismic performance of FRP strengthened RC membersQuasi-static lateral load test of FRP strengthened full scale RC columns

Experimental lateral load-displacement curves

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90-500-400-300-200-100

0100200300400500

S1H1C0N2 S1H1C3N2

Late

ral f

orce

P (k

N)

Lateral displacement (mm)

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90-500-400-300-200-100

0100200300400500

S1H1C3N2 S1H1C4N2

Late

ral f

orce

P (k

N)


-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90-300

-200

-100

0

100

200

300

C1H1C3N2 C1H1G3N2

Late

ral f

orce

P (k

N)


-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90-300

-200

-100

0

100

200

300

C1H1C0N2 C1H1C3N2

Late

ral f

orce

P (k

N)


Open System for Earthquake Engineering SimulationOpensees:


Finite element analysis on seismic performance of FRP-confined RC columns

1 1

2 2

NP

Nonlinear Beam-Column Element

Cover

Core

1-1

2-2

Steel

FRP-confined

Element and Fiber Section used in OpenSees





-0.010 -0.005 0.000 0.005 0.010 0.015 0.020 0.025-450

-360

-270

-180

-900

90

180

270

360

450A

xial

stre

ss

c (MPa

)

Axial strain c

Steel02

0.000 0.002 0.004 0.006 0.008 0.010

5

10

15

20

25

30

35

unconfined concrete

Axi

al st

ress

c (M

Pa)

Axial strain c

Concrete01

0.000 0.003 0.006 0.009 0.012 0.015

5

10

15

20

25

30

35

Steel-confined concrete

Axi

al st

ress

c (M

Pa)

Axial strain c

Concrete01

0.000 0.007 0.014 0.021 0.028 0.035

9

18

27

36

45

Axi

al st

ress

c (M

Pa)

Axial strain c

FRP-confined concrete

Steel Unconfined concrete

Steel-confined concrete FRP-confined concrete

Comparison between simulation and experimental results

Seismic performance of FRP strengthened RC membersFinite element analysis on seismic performance of FRP-confined RC columns

-80 -60 -40 -20 0 20 40 60 80-300

-200

-100

0

100

200

300

Simulation Experiment

Late

ral f

orce

P (k

N)

Lateral load (mm)

C1H1C3N2

-80 -60 -40 -20 0 20 40 60 80-300

-200

-100

0

100

200

300


Late

ral f

orce

P (k

N)


C1H1G3N2

-60 -40 -20 0 20 40 60-300

-200

-100

0

100

200

300


Late

ral f

orce

P (k

N)

Lateral displaciment (mm)

S2H1C2N2

-100 -80 -60 -40 -20 0 20 40 60 80 100-500-400-300-200-100

0100200300400500


Late

ral f

orce

P (k

N)


S1H1C4N2


Quasi-static lateral load test of FRP strengthened full scale RC beam-column joints

Interior beam-column joints

Test setup



Specimen Retrofitting patterns

J0 Control specimen (without strengthening)

J1 Strengthen columns only

J2 Strengthen columns + beams (U-shape FRP stripe)

J3 Strengthen columns + beams (lateral wrapped FRP)


Top column Core area of joint SlabBeam Bottom columnJ0 J0 J0 J0 J0

J1 J1 J1 J1 J1

J2 J2 J2 J2 J2

J3 J3 J3 J3 J3


-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300

J0

Late

ral f

orce

P (k

N)


-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300

J2

Late

ral f

orce

P (k

N)


-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300

J3

Late

ral f

orce

P (k

N)


-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300

Late

ral f

orce

P (k

N)


J1


Experimental lateral load-displacement curves


Finite element analysis of FRP strengthened RC beam-column joints

-0.010 -0.005 0.000 0.005 0.010 0.015 0.020 0.025-450

-360-270

-180-90

090

180

270360

450

Axi

al st

ress

c (M

Pa)

Axial strain c

Steel02

0.000 0.007 0.014 0.021 0.028 0.035

9

18

27

36

45

Axi

al st

ress

c (M

Pa)

Axial strain c


0.000 0.002 0.004 0.006 0.008 0.010

5

10

15

20

25

30

35

unconfined concrete

Axi

al st

ress

c (M

Pa)

Axial strain c

Concrete01

0.000 0.003 0.006 0.009 0.012 0.015

5

10

15

20

25

30

35

Steel-confined concrete

Axi

al st

ress

c (M

Pa)

Axial strain c

Concrete01

NF

Joint2D

NolinearBeamColumn

NolinearBeamColumn

NolinearBeamColumn

NolinearBeamColumn

SteelSteel02

Unconfined concrete Concrete01

Steel-confined concreteConcrete01


Pinching4 Material (modified diagonal compression field theory (MCFT))

OpenSees FE modeling

deformation

force


Finite element analysis of FRP strengthened RC beam-column joints

-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300


Late

ral f

orce

P (k

N)


J2

-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300


Late

ral f

orce

P (k

N)

水平位移 (mm)

J3

-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300


Late

ral f

orce

P (k

N)


J1

-200 -150 -100 -50 0 50 100 150 200-300

-200

-100

0

100

200

300


Late

ral f

orce

P(k

N)


J0

Comparison between simulation and experimental results


Research background




Shaking table test of FRP retrofitted large scale nunductile RC frames

Seismic performance of FRP retrofitted RC frames

Dimensions, general view and reinforcement details of test frame



Properties Physical quantities Similitude equation Model Remarks

Material

Strain ε 1.0Stress σ 1.0Elastic modulus E 1.0 Model design controlPoisson ratio μ 1.0Density ρ 1.008

Geometric

Length l 1/2 Model design controlArea S 1/4linear displacement X 1/2angular displacement β 1.0

LoadConcentrated force P 1/4Linear Load q 1/2

Dynamic

Mass m 0.126Stiffness K 1/2Time t 0.502 Dynamic loading controlFrequency f 1.992 Dynamic loading controlDamping c 0.251Velocity v 0.996Acceleration a 1.984 Dynamic loading control

Similitude relations for dynamic model testing



CFRP retrofit strategies



Measurement system

LVDT

LVD

T

accelerometer

accelerometer

accelerometer

Shaking Table: 5m× 5m, Maximum load capacity 30t



0 2 4 6 8 10 12 14 16 18 20-0.8

-0.4

0.0

0.4

0.8

1.2

Acc

eler

atio

n (g

)

Time (s)

Northridge X

0 2 4 6 8 10 12 14 16 18 20-1.2

-0.8

-0.4

0.0

0.4

0.8

Acc

eler

atio

n (g

)

Time (s)

Kobe X

0 2 4 6 8 10 12 14 16 18 20-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

Acc

eler

atio

n (g

)

Time (s)

Kobe Y

0 2 4 6 8 10 12 14 16 18 20-0.8

-0.4

0.0

0.4

0.8

1.2

Acc

eler

atio

n (g

)

Time (s)

Northridge Y

0 2 4 6 8 10 12 14 16 18 20-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

Acc

eler

atio

n (g

)

Time (s)

El Centro X

The ground motion records selected based on:Maximum displacement capacity of shaking tableNatural frequency of test model

Failure modes of unstrengthened RC control frame



The maximum applied peak ground acceleration (PGA) can be resisted by the bare frame specimen was approximately equal to 0.6g.



Failure modes of FRP retrofitted frame

The can be resisted maximum PGA by the strengthened frame was more than 1.0g.The seismic performance improved about 1 times.



The peak relative displacement at each storey of CFRP retrofitted frame is much smaller than that of bare frame under the similar input PGA level

0 10 20 30 40 50 60 70 80

1

2

3

4

5

0.7g0.3g 0.6g0.3g

Stor

eys

Relative displacement (mm)

Bare Strengthened

Northridge (X direction)(a)

0 30 60 90 120 150

1

2

3

4

5

0.15g 0.7g0.15g 0.6g

Stor

eys

Relative Displacement (mm)

Bare Strengthened

Northridge (Y direction)(b)

0 15 30 45 60 75

1

2

3

4

5

Stor

eys

Relative displacement (mm)

Bare Strengthened

Northridge (Y direction 0.3g)(c)

0 30 60 90 120 150

1

2

3

4

5

0.3g 0.7g 0.6g0.3g

Stor

eys

Relative Displacement (mm)

Bare Strengthened

Kobe (Y direction)(d)



The inter-storey drift ratio at each storey of retrofitted frame is smaller than that of bare frame under the similar earthquake level, especially in Y direction.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1

2

3

4

5

0.3g0.3g

Bare Strengthened

Stor

eys

Inter-storey drift ratio (%)

X direction(a)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1

2

3

4

5

Bare Strengthened

0.7g0.6g

Stor

eys


X direction(b)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1

2

3

4

5

0.3g

Stor

eys


Bare Strengthened

Y direction(c)

0.3g

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1

2

3

4

5

0.6g0.7g0.15gSt

orey

s


Bare Strengthened

Y direction

0.15g

(d)

Finite element analysis of FRP retrofitted large scale nunductile RC frames


FE modeling based on OpenSees

Beam element1B element2

Column element3

Column element2

Column element1

Steel reinforcement

FRP strips

Fiber section of beam

Fiber section of column

Steel reinforcementFRP strips




0 1 2 3 4 5 6 7 8 9 10 11 12 13 14-0.6

-0.3

0.0

0.3

0.6

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14-0.8

-0.4

0.0

0.4

0.8

2rd floorAcc

eler

atio

n (g

)

Time (s)

Northridge X (0.3g)

RoofAcc

eler

atio

n (g

)

Time (s)

Experiment Simulation

0 2 4 6 8 10 12 14 16 18-1.2

-0.6

0.0

0.6

1.2

0 2 4 6 8 10 12 14 16 18-1.4

-0.7

0.0

0.7

1.4

2rd floorAcc

eler

atio

n (g

)

Time (s)

El Centro X (0.7g)

RoofAcc

eler

atio

n (g

)

Time (s)


0 1 2 3 4 5 6 7 8 9 10 11 12-0.8

-0.4

0.0

0.4

0.8

0 1 2 3 4 5 6 7 8 9 10 11 12-1.0

-0.5

0.0

0.5

1.0

2rd floorAcc

eler

atio

n (g

)

Time (s)

Kobe X (0.3g)

RoofAcc

eler

atio

n (g

)

Time (s)


0 1 2 3 4 5 6 7 8 9 10 11 12-1.6

-0.8

0.0

0.8

1.6

0 1 2 3 4 5 6 7 8 9 10 11 12-2

-1

0

1

2

2rd floorAcc

eler

atio

n (g

)

Time (s)

Kobe X (0.7g)

RoofAcc

eler

atio

n (g

)

Time (s)


Comparison between simulation and test results of acceleration time history



Comparison between simulation and test results of displacement time history

0 2 4 6 8 10 12 14 16 18-30

-15

0

15

30

0 2 4 6 8 10 12 14 16 18-30

-15

0

15

30

2rd floor

Dis

plac

emen

t (m

m)

Time (s)

El Centro X (0.3g)

Roof

Dis

plac

emen

t (m

m)

Time (s)


0 1 2 3 4 5 6 7 8 9 10 11 12-40

-20

0

20

40

0 1 2 3 4 5 6 7 8 9 10 11 12-40

-20

0

20

40

2rd floor

Dis

plac

emen

t (m

m)

Time (s)

Kobe X (0.3g)

Roof

Dis

plac

emen

t (m

m)

Time (s)


1 2 3 4 5 6 7 8 9 10 11 12 13 14-20

-10

0

10

20

1 2 3 4 5 6 7 8 9 10 11 12 13 14-20

-10

0

10

20

2rd floorDis

plac

emen

t (m

m

Time (s)

Northridge X (0.3g)

RoofDis

plac

emen

t (m

m)

Time (s)


0 2 4 6 8 10 12 14 16 18-50

-25

0

25

50

0 2 4 6 8 10 12 14 16 18-60

-30

0

30

60

2rd floor

Dis

plac

emen

t (m

m)

Time (s)

El Centro X (0.7g)

Roof

Dis

plac

emen

t (m

m)

Time (s)


Thanks for your attention

Documents

Experimental and analytical investigation of seismic ...web/@eis/@research/...Experimental and analytical investigation of seismic performance of nonductile RC frames strengthened