CFRP OVERLAYS INCFRP OVERLAYS IN

STRENGTHENING OFSTRENGTHENING OF

FRAMES WITH COLUMN REBARFRAMES WITH COLUMN REBAR

LAP SPLICE PROBLEMLAP SPLICE PROBLEM

ByBy

ŞŞevket evket ÖÖzden zden (Kocaeli (Kocaeli UnivUniv. Turkey). Turkey)

Umut Umut AkgAkgüüzelzel ((BogaziciBogazici UnivUniv. Turkey). Turkey)

FundedFunded byby METU METU ProjectsProjects::

NATO NATO SfPSfP977231977231

TTÜÜBBĐĐTAKTAK--ĐĐÇÇTAG I575TAG I575

Introduction

Turkish Earthquake Codeimpel the designer to provide adequate

stiffness, strength and ductility.

The structure should :

•resist the moderate earthquakes with some architecturaldamage but without any significant structural damage.

•the structure is expected to survive without collapse in the event of a major eartquake.

Review of System Strengthening Techniques

• Addition of R/C shear walls

• Addition of cast-in-place reinforced concrete panel orprecast concrete wall panels

• Application of an external coating / overlay such as;sprayed technique, glass or steel fiber reinforced concrete

coating

CommonDrawbacks

• Require great deal of surface preparation and formwork

• Add considerable weight to the structure

• Accompanied with a great deal of disturbance while the structure is undergoing rehabilitation

An Alternative Strengthening Method: Retrofit by Using FRP

Objective:

to understand the performance and failuremechanism of the r/c frames strengthened withCFRP overlays applied to the masonry infill panels.

Constitutive laws of FRP

σ

ε

Carbon-FRP

Aramid-FRP

Glass-FRP

Steel

Constitutive laws of FRP

σ

ε

Carbon-FRP

Aramid-FRP

Glass-FRP

Steel

Test Specimens - Dimension and Reinforcement

Test specimens

•one-third scale

•one-bay, two-story frames

Frames with deficiencies

• improper anchorage

• poor confinement

• no reinforcement at beam-column joints

• inadequate lap splicelength in columns

Lap Splice

6φ8

6φ8

6φ14

150

750

150

150

150

400

450

16

0

100 12@1300 100

330

285 285

33050

7@

650

40

0750

50

5@500 4@500200

150 300 150300

16

0

200 1500 200

50

150

150

6φ8

6φ8

6φ14

150

750

150

150

150

400

450

16

0

100 12@1300 100

330

285 285

33050

7@

650

40

0750

50

5@500 4@500200

150 300 150300

16

0

200 1500 200

50

150

150

6φ8

6φ8

6φ14

150

750

150

150

150

400

450

16

0

100 12@1300 100

330

285 285

33050

7@

650

40

0750

50

5@500 4@500200

150 300 150300

16

0

200 1500 200

50

150

150

150

750

150

150

150

400

450

16

0

100 12@1300 100

330

285 285

33050

7@

650

40

0750

50

5@500 4@500200

150 300 150300

16

0

200 1500 200

50

150

150

Test SpecimensDimension and Reinforcement Properties

Mechanical Properties of Materials

Specimen Type Column

Rein.

Beam

Rein.

Lap

splice

Frame Concrete

Strength

Mortar

Strength

(mm) (MPa) (Mpa)

Spc-U1 BARE 4

Φ8 6

Φ8 160 15.4 -

Spc-U2 INFILLED 4

Φ8 6

Φ8 160 14.8 5.5

Spc-U3 INFILLED 4

Φ8 6

Φ8 160 16.1 5.1

Spc-U4 INFILLED 4

Φ8 6

Φ8 160 15.3 3.8

Spc-U5 INFILLED 4

Φ8 6

Φ8 160 14.4 4.7

Specimen Type Column

Rein.

Beam

Rein.

Lap

splice

Frame Concrete

Strength

Mortar

Strength

(mm) (MPa) (Mpa)

Spc-U1 BARE 4

Φ8 6

Φ8 160 15.4 -

Spc-U2 INFILLED 4

Φ8 6

Φ8 160 14.8 5.5

Spc-U3 INFILLED 4

Φ8 6

Φ8 160 16.1 5.1

Spc-U4 INFILLED 4

Φ8 6

Φ8 160 15.3 3.8

Spc-U5 INFILLED 4

Φ8 6

Φ8 160 14.4 4.7

Material TypeYield

Strength

Ultimate

Strength

fyk fu

(Mpa) (Mpa)

Tensile E-modulus

(Mpa)

198,600

194,400

Stirrup

Long. Rein.Steel

N/A 3,500

380 518

241 423

CFRP fibers

Adhesive N/A 30

230,000

3,800

100mm 130mm

7 ~ 8mm

150mm

100mm

Plaster

Column

Brick Infill

Brick Infill and Plastering Detail

70mm

100mm 130mm

7 ~ 8mm

150mm

100mm

Plaster

Column

Brick Infill

Brick Infill and Plastering Detail

70mm

Test Specimens - Infill

• Scaled down tiles

• Low strength mortar and plaster.

STRONG FLOOR

X - Beam

Hydraulic

JackRoller Support

Vertical

Spreader Beam

Steel Rod

Steel

Bracing

Axial

Load Frame

Hinge Support

Out-of-plane

Restrainer

ADAPTOR FOUNDATION

ACTUATOR

REACTION WALL

Horizontal

Spreader Beam

SPECIMENHigh

Strength

Steel Bolt

Test Procedure - Test Set-up

Test Procedure – Loading Pattern

-60

-40

-20

0

20

40

60

0 1 2 3 4 5 6 7

1

1

2

2

3

3

4

4

5

5

6

6

7

7-60

-40

-20

0

20

40

60

0 1 2 3 4 5 6 7

1

1

2

2

3

3

4

4

5

5

6

6

7

7

1

1

2

2

3

3

4

4

5

5

6

6

7

7-10

-8

-6

-4

-2

0

2

4

6

8

10

7 8 9 10 11 12 13 14 15 16

108

8

9

9 10

11

11

12

12

13

13

14

14

15

15-10

-8

-6

-4

-2

0

2

4

6

8

10

7 8 9 10 11 12 13 14 15 16

108

8

9

9 10

11

11

12

12

13

13

14

14

15

15

Dis

pla

cem

ent

Du

ctil

ity R

atio

Ap

pli

ed L

oad

(kN

)

Cycle No.Load controlled phase Displacement controlled phase

-60

-40

-20

0

20

40

60

0 1 2 3 4 5 6 7

1

1

2

2

3

3

4

4

5

5

6

6

7

7-60

-40

-20

0

20

40

60

0 1 2 3 4 5 6 7

1

1

2

2

3

3

4

4

5

5

6

6

7

7

1

1

2

2

3

3

4

4

5

5

6

6

7

7-10

-8

-6

-4

-2

0

2

4

6

8

10

7 8 9 10 11 12 13 14 15 16

108

8

9

9 10

11

11

12

12

13

13

14

14

15

15-10

-8

-6

-4

-2

0

2

4

6

8

10

7 8 9 10 11 12 13 14 15 16

108

8

9

9 10

11

11

12

12

13

13

14

14

15

15

Dis

pla

cem

ent

Du

ctil

ity R

atio

Ap

pli

ed L

oad

(kN

)

Cycle No.Load controlled phase Displacement controlled phase

Two Phase Loading Pattern

•load control

•displacement control

Each test continued untilthe specimenexperienced a

significant loss of capacity.

Test Results – Specimen-U1

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Roof Drift (∆∆∆∆/h) (mm/mm)

Ba

se

Sh

ea

r (k

N)

Specimen: U1

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Roof Drift (∆∆∆∆/h) (mm/mm)

Ba

se

Sh

ea

r (k

N)

Specimen: U1

Test Results – Specimen-U2

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Base

Sh

ea

r (k

N)

Specimen: U2

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Base

Sh

ea

r (k

N)

Specimen: U2

Test Results – Specimen-U3

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Ba

se S

hea

r (

kN

)

Specimen: U3

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Ba

se S

hea

r (

kN

)

Specimen: U3

Test Results – Specimen-U4

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Bas

e S

he

ar

(kN

)

Specimen: U4

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Bas

e S

he

ar

(kN

)

Specimen: U4

Test Results – Specimen-U5

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Base S

hear

(kN

)

Specimen: U5

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04

Roof Drift (∆∆∆∆/h) (mm/mm)

Base S

hear

(kN

)

Specimen: U5

-150

-100

-50

0

50

100

150

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

Top Displacement (mm)

Ba

se

Sh

ea

r (k

N)

U2U1

U3

U5

U4

-150

-100

-50

0

50

100

150

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

Top Displacement (mm)

Ba

se

Sh

ea

r (k

N)

U2U1

U3

U5

U4

Evaluation of Test Results Strength

SpecimenPmax

(kN)

U1 11.2

U2 59.4

U3 74.6

U4 95.7

U5 115

1.61

Comparison of Lateral Load Capacities

1.94

Pmax Variation

0.19

1

1.26

Pmax,Ui

Pmax,U2

Evaluation of Test Results Stiffness

• Failure of infill panels at the first story level resulted in a sudden drop of stiffness(when the roof drift reached approximately 0.5%.)

• The stiffness degradation of all specimens stabilized beyond the drift level of 1%.

• Stiffness degradation of Specimen-U5 was relatively at a slow pace rate.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.000 0.005 0.010 0.015 0.020 0.025

Drift Ratio

No

rma

lize

d P

eak

to

Pe

ak S

tiff

ness

U2

U1

U3

U5

U4

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.000 0.005 0.010 0.015 0.020 0.025

Drift Ratio

No

rma

lize

d P

eak

to

Pe

ak S

tiff

ness

U2

U1

U3

U5

U4

0

2

4

6

8

10

12

14

16

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045

Drift Ratio

Cu

mu

lati

ve E

ne

rgy D

issip

ate

d (

kN

m)

U2U1

U3

U5

U4

0

2

4

6

8

10

12

14

16

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045

Drift Ratio

Cu

mu

lati

ve E

ne

rgy D

issip

ate

d (

kN

m)

U2U1

U3

U5

U4

Evaluation of Test Results Energy Dissipation

• All specimens except bare frame (Sp-U1) dissipated almost the sameamount of energy up to the 0.5% roof drift ratio.

•Although a drastic drop in equivalent viscous damping ratio is observedbetween the roof drift levels of 0.2% and 0.5%, damping ratios yieldedrelatively high values for roof drift ratios beyond 0.5%.

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.4

0.4

0.5

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045

Drift Ratio

Eq

uiv

ale

nt

Da

mp

ing

Ra

tio

U2U1

U3

U5

U4

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.4

0.4

0.5

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045

Drift Ratio

Eq

uiv

ale

nt

Da

mp

ing

Ra

tio

U2U1

U3

U5

U4

Evaluation of Test Results Residual Displacement

• Residualdisplacement is characterized by the ratio of permanentdeflection to the maximum deflectionexperienced at a given drift level.

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045

Drift Ratio

Resid

ua

l D

isp

lacem

en

t R

ati

o

U2

U1

U3

U5

U4

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045

Drift Ratio

Resid

ua

l D

isp

lacem

en

t R

ati

o

U2

U1

U3

U5

U4

Conclusions

•The proposed X-overlay CFRP reinforcement scheme resulted in

- stronger specimen

- gradual and prolonged failure

- more energy dissipation

- stable post peak behavior

- Low stiffness enhancement

•Changes in CFRP details resulted in drastic changes in the behavior of the specimens

•Interstory drift level of 0.35%˜0.50% may be a limiting valuepreventing the CFRP modified masonry from degradation

Recommendations for Future Studies

• The influence of frame aspect ratio

•The effect of partial infilling as well as infill with openings

CFRP OVERLAYS INCFRP OVERLAYS IN

STRENGTHENING OFSTRENGTHENING OF

FRAMES WITH COLUMN REBARFRAMES WITH COLUMN REBAR

LAP SPLICE PROBLEMLAP SPLICE PROBLEM

ByBy

ŞŞevket evket ÖÖzden zden (Kocaeli (Kocaeli UnivUniv. Turkey). Turkey)

Umut Umut AkgAkgüüzelzel ((BogaziciBogazici UnivUniv. Turkey). Turkey)

FundedFunded byby METU METU ProjectsProjects::

NATO NATO SfPSfP977231977231

TTÜÜBBĐĐTAKTAK--ĐĐÇÇTAG I575TAG I575