behavior, design and monitoring of concrete structures ... 2_jg ten… · behavior, design and...

Behavior, Design and Monitoring of Concrete Structures Strengthened

with Fibre-Reinforced Polymer (FRP) Composites

Jin-Guang Teng, BEng, PhD, FHKIE Chair Professor of Structural Engineering

The Hong Kong Polytechnic University

OUTLINE OF THE PRESENTATION

Introduction Bond behaviour between FRP and

concrete Flexural strengthening of beams Shear strengthening of beams Strengthening of columns Seismic retrofit Near surface mounted FRP reinforcement Monitoring and other research at PolyU

SOME BASIC FACTS OF FRP COMPOSITES

Classification Based on Fibre Types GFRP = Glass Fibre-Reinforced Polymer/Plastic CFRP = Carbon Fibre-Reinforced Polymer/Plastic AFRP = Aramid Fibre-Reinforced Polymer/Plastic

Forming Methods Prefabrication, Particularly Pultrusion

Better Quality Control

Wet Lay-Up Using Fibre/Woven Fabric Sheets

Greater Flexibility

Woven Glass Fabric for Wet Lay-Up Applications

Carbon Fibre Sheet for Wet Lay-Up Applications

CFRP Pultruded Plate

FRP bars

Bridge deck Concrete-filled FRP tube

OTHER FRP PRODUCTS/APPLICATIONS

FRP COMPOSITES IN CONSTRUCTION: EXISTING RESEARCH

The majority of published research isstill concerned with FRP strengtheningof concrete structures

Hybrid structures of FRP and concrete(or another traditional material) are attractive

In terms of new construction, FRP composites are particularly promisingfor new bridges

FRP REINFORCING BARS

Top Mat for Bridge Decks: FRP Bars from Hughes Brothers

Replace steel bars in corrosive environments

Courtesy of Prof A Mufti, University of Manitoba

MANITOBA FLOODWAY PROJECT STEEL-FREE CONSTRUCTION

Because of ISIS Canadas research and influence, the 6 new highway bridges overthe Winnipeg Floodway will have GFRPs in the decks (45,000 square metres). Some ofthese bridges will also have SHM.

This is a mega project estimated to cost$700 million, and is therefore, comparableto the one billion dollar Confederation Bridge project completed in 1995.

(Courtesy of Prof Mufti)

FRP IN CONCRETE STRUCTURES: GROWTH OF SCI PAPERS SINCE 1990

Results from a keyword search using FRP and concrete

0 3 6 4 7 11 16 18

26 32

56

83 93

117119 134

197

227

0

50

100

150

200

250

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Year

Num

ber o

f SC

I pap

ers

FRP STRENGTHENING OF STRUCTURES

Strengthening of RC members: flexural,shear and confinement

Retrofit of RC structures for seismic and blast resistance

Strengthening of steel, masonry andtimber structures

Use of pre-stressed and hybrid FRP


Introduction 9 FRP strengthening of RC Structures

Bond behaviour between FRP and concrete

Flexural strengthening of beams Shear strengthening of beams Strengthening of columns Seismic retrofit Near surface mounted FRP reinforcement Monitoring and other research at PolyU

FRP STRENGTHENING OF RC STRUCTURES: EXAMPLE PRACTICAL APPLICATIONS

Flexural Strengthening of a highway RC bridge slab

Flexural Strengthening of a two-way slab in a building

Strengthening a circular column

Strengthening of a water pumping station

Courtesy of Prof LP Ye, Tsinghua University

FRP STRENGTHENING OF RC STRUCTURES: EXAMPLE LABORATORY TESTS

FRP STRENGTHENING OF RC STRUCTURES: RESEARCH PRIOR TO 2002

Concrete Society(2000, 2004)

fib (2001) ISIS (2001) JSCE (2001) ACI 440 (2002) More afterwards

Design guidelines forexternally bondedFRP reinforcement for strengtheningconcrete structures

CHINESE TECHNICAL SPECIFICATIONS

NERCProduction and quality control of adhesives

Specification of Adhesives used for Construction Strengthening

NERCProduction and quality control of laminated CFRP

Specification of Carbon Fiber Polymer used for Construction Strengthening

NERCDesign methods for flexural, shear and seismic strengthening

Technical Specification for Strengthening Concrete Structures with Carbon Fiber Reinforced Polymer

Coordinator Scope of applicationTitle of Document

Technical Specification for Strengthening Concrete Structures with Carbon Fiber Reinforced Polymer

NATIONAL STANDARD A national standard of China for the structural use of FRP composites in construction has been under development since 2002. The standard is now nearing completion. Topics covered by this standard include:

9FRP materials 9Strengthening of RC structures 9Strengthening of masonry structures 9Concrete beams reinforced or prestressed with FRP 9FRP-concrete hybrid structures

WHY FRP COMPOSITES? ADVANTAGES:

Have All the Advantages of Steel Plates for Plate Bonding

Speedy application; Minimal increases in structural weight and size.

High Strength/Weight Ratio Lifting equipment eliminated; Reduced labour cost.

Flexibility in Shape Can be handled in rolls; easy for wrapping on curved surfaces and around columns.

High Resistance to Corrosion and Other Chemical Attacks

Durable performance.

WHY FRP COMPOSITES?

DISADVANTAGES:

High material cost Lack of ductility Poor fire resistance

Overall:

Cost-effective retrofit solutions

TYPICAL STRESS-STRAIN CURVES OF FRP COMPOSITES AND STEEL

0.0 0.5 1.0 1.5 2.0 2.5 3.0 0

500

1000

1500

2000

2500

3000

Mild steel

GFRP

Stre

ss (M

Pa)

Strain (%)

CFRP

BOND STRENGTH BY SINGLE-SHEAR PULL-OFF TEST

lfrp=95mm

DEBONDING FAILURE

BEHAVIOUR OF BONDED JOINTS

Failure generally occurs in the concrete adjacent to the adhesive-to-concrete interface

An increase of bond length L may not increase the bond strength.

Tensile strength of plate may not be reached at failure.

Bonded plate Concrete

P

L

CHEN AND TENGS BOND STRENGTH MODEL: EQUATIONS

Modified from a nonlinear fracture mechanics model: Pu =0.427pL fc' bpLe

Le = Eptp

fc ' ,

L = 1 if L Le

sin L 2Le if L < Le

p = 2 bp/bc 1 + bp/bc

P L

bp bc

FLEXURAL STRENGTHENING OF BEAMS

RC beam

Soffit plate

Adhesive layer

A Section A

CONVENTIONAL FAILURE MODES OF RC BEAMS BONDED WITH AN FRP SOFFIT PLATE

FRP Rupture

(a) FRP rupture

Concrete Crushing

(b) Crushing of compressive concrete

DEBONDING FALURES OF FRP-PLATED RC BEAMS: CLASSIFICATION OF MODES

Debonding

Flexural crack

Debonding Critical diagonal crack

(a) IC debonding (b) CDC debonding

Debonding

Debonding

Debonding (c) CDC debonding with concrete cover separation (d) Concrete cover separation

Debonding Debonding Debonding (e) Concrete cover separation under pure bending (f) Plate end interfacial debonding

Intermediate crack debonding: (a) Plate end debonding: (b) to (f)

CRITICAL DIAGONAL CRACK (CDC) DEBONDING

CDC DEBONDING FOLLOWED BY CONCRETE COVER SEPARATION

CONCRETE COVER SEPARATION

Concrete Cover Separation

CONCRETE COVER SEPARATION: CLOSE-UP

Steel tension reinforcement

PLATE END INTERFACIAL DEBONDING

PREDICTION OF PLATE END DEBONDING FAILURES

Pure shear debonding

Pure flexural debonding

A new debonding strength model based on shear-bending interaction

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.2 0.4 0.6 0.8 1.0 1.2 M db,end /M db,f

V db,

end

/Vdb

,s

Ceroni et al. (2001) Fanning and Kelly (2001) Rahimi and Hutchinson (2001) Nardo et al. (2003) Pornpongsaroj and Pimanmas (2003) Smith and Teng (2003) For pure shear debonding force

PLATE END FAILURES CAN BE SURPRESSED BY U JACKETS

Steel tension reinforcement

PREVENTION OF PLATE END FAILURES

RC beam

Tension face plate Section A-A

U Jacket

A

A

How should be U jackets be designed and detailed?

INTERMEDIATE CRACK (IC) INDUCED INTERFACIAL DEBONDING

Debonding at concrete-to-adhesive interface due to high stresses which originate from a major flexural or flexural-shear crack away from the plate ends

INTERMEDIATE CRACK (IC) DEBONDING IN AN FRP-PLATED RC BEAM

A better understanding A finite element model for

IC debonding A new IC debonding

strength model

A number of recent studies in collaboration with Tsinghua University have led to

SHEAR STRENGTHING OF RC BEAMS

FRP Bonding Configurations Side bonding U-jacketing Wrapping

FRP Reinforcement Distributions Strips Plates/sheets

FRP Fibre Orientations: Various Angles

METHODS OF SHEAR STRENGTHENING FRP fibre orientation(s) Bond scheme and notation

h

h f h f h f

=90 SS90 US90 WS90

0

LIKELY FAILURE MODES

Wrapping: Rupture Shear crack

FRP fracture starts here

Debonded zone

Shear crack

Shear crack

debonded zone

U-jacketing: Debonding or Rupture

Side Bonding: Debonding

FRP RUPTURE FAILURE OF A SHEAR-STRENGTHENED BEAM

FAILURE OF SHEAR-STRENGTHENED BEAM BY DEBONDING

SHEAR CAPACITY

z Shear Capacity of Shear-Strengthened Beams:

9 Vc = shear capacity of concrete 9 Vs = contribution of steel shear

reinforcement 9 Vfrp = contribution of FRP

z Vc & Vs calculated using provsions in an existing code

Vn = V c +Vs + Vfrp

STRENGTHENING OF COLUMNS BY FRP CONFINEMENT

Wrapping

Filament Winding

Prefabricated Shell Jacketing

TYPICAL FAILURES OF FRP-CONFINED CONCRETE CYLINDERS

GFRP-wrapped cylinder CFRP-wrapped cylinder

r 2R

r

t

Efrpth Efrpth

Concrete FRP jacket 2R

c

r

CONFINEMENT OF CONCRETE BY AN FRP JACKET

R tE hfrp

r

=

FLAT COUPON TENSILE TEST OF FRP (E.G. ASTM D3039 1995)

b 56 138 56

FRP

t Aluminum tab

Strain gauge

STANDARD CONFINED CYLINDER TEST FOR THE DETERMINATION

OF FRP EFFICIENCY FACTOR

FRP Efficiency Factor = Ratio of the actual FRP hoop rupture strain to the FRP rupture strain from flat coupon tests

Manufacturers should carry out such tests to determine the FRP efficiency factor for confinement applications

INCREASING AND DECREASING TYPES OF STRESS-STRAIN CURVES

cu Axial strain c

' cof

' ccf

Axia

l stre

ss

c

cu

' cof

' ccf

Axi

al s

tress

c

' cuf

cc

Axial strain c cu

' cof

' ccf

Axi

al s

tress

c

' cuf

cc

1'' cocu ff

weakly-confined

moderately-confined

heavily-confined

STRESS-STRAIN MODELS

Design-oriented models (closed-form expressions)

Analysis-oriented models (incremental iterative numerical procedures)

LAM AND TENGS DESIGN-ORIENTED MODEL FOR FRP-CONFINED CONCRETE

( ) 2 '

2 2

4 c co c

ccc f EE

E

= tc0

c2 '

coc Ef += cuct

)( 2

2

'

EE f

c

co t

= cu

cocc ffE

''

2

=

45.0,

'1275.1/

+=

co

ruph

co

l cocu f

f

''

'

3.31 co

l

co

cc

f f

f f

+=

R tE

f ruphfrp l , =

LAM AND TENGS STRESS-STRAIN MODEL

Axial Strain, c

Axi

al S

tress

,

c

Unconfined Concrete (GB 50010) FRP-confined Concete (Lam and Teng)

f cc

f co

co t 0.0033 cu

Efrp = 250 GPa

h, rup = 0.00982

t = 0.33 mm

d = 152 mm

fco = 35.9 mm

COMPARISON WITH TEST DATA Design-oriented models using test FRP

hoop rupture strains

0

10

20

30

40

50

60

70

80

90

0 0.005 0.01 0.015 0.02 0.025

Axial strain c

Axi

al s

tress

c (

MPa

)

Test (3 specimens)Samaan et al. [12]Miyauchi et al. [44]Saafi et al. [28]Toutanji [27]Cheng et al. [48]Jin [30]Moran and Pantelides [31] Lam and Teng [21]Xiao and Wu [49]

f'co = 35.9 MPa Efrp = 250546 MPa frp = 0.00152 h,rup = 0.00982 t =0.33 mm R = 76 mm

2-Ply CFRP

Response of confining device (FRP)

Axial response of concrete core

Deformation of concrete core

TENG ET ALS ANALYSIS-ORIENTED MODEL FOR CONFINED CONCRETE

D Et ljj

l

2 =

co

l

co

cc

ff f

' 5.31

' '*

+= co

l

co

cc

f ' 5.171

*

+=

( ) ( )

*

*

* 1' ccc ccc

cc

c

f + =

**' ccccc c

fE E

=

+

+=

co

l

co

l

co

l

co

c

f

7exp75.018185.0

7.0

'

0

0.5

1

1.5

2

0 2 4 6 8 Normalized axial strain c/co

Nor

mal

ized

axi

al s

tress

c /f

' co

Unconfined

Confined with a constant pressure

Confined with FRP

Peak stress and strain of concrete confined with

(c/f'co, c/co)

l

(f*cc/f'co, * cc/co)

l

f'cc/f'co

cu/co

Generation of a stress-strain curve

ANALYSIS-ORIENTED MODEL

COMPARISON WITH TEST DATA Analysis-oriented models, GFRP-confined specimens

Efrp = 21.8 GPa

h, rup = 0.01718

t = 0.33 mm

d = 152 mm

fco = 38.5 mm

0

10

20

30

40

50

60

70

80

90

0.000 0.010 0.020 0.030 0.040 0.050

Axial strain c

Axia

l stre

ss

c (M

Pa)

Test (2 specimens)Harmon et al. [13] Spoelstra and Monti [29]Fam and Rizkalla [53]Chun and Park [54]Harries and Kharel [14]Becque et al. [56]Huang et al. [15]

f'co = 38.5 MPa Efrp = 21800 MPa h,rup = 0.01718 t =2.54 mm R = 76 mm

2-Ply GFRP

COMPARISON BETWEEN NEW MODEL AND TEST RESULTS OF STEEL-CONFINED CONCRETE

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0

300

600

900

1200

1500

1800

2100 A

xial

load

(kN

)

Axial strain

f 'c=26.7MPa test f 'c=26.7MPa predicted f 'c=37.0MPa test f 'c=37.0MPa predicted f 'c=47.5MPa test f 'c=47.5MPa predicted

Analysis-oriented model of Teng et al. versus test results of Xiao et al.

STRENGTHENING OF SHORT COLUMNS: SECTION ANALYSIS USING A DESIGN-ORIENTED

AXIAL STRESS-STRAIN MODEL

xn

R

si

bc

d

cu

sid

' ccf

si

1 ( )

nR

u c c si c si R x i

N b d A

=

=

= +

1 ( )

nR

u c c si c si siR x i

M b d A d

=

=

= +

2 1

2

,

60 (1 ) 20

(1 0.06 )h rupcccoco

e eD e

ff

+

+

SLENDERNESS LIMIT FOR SHORT COLUMNS

0 50 100 150 200 250 3000

50

100

150

200

250

300

Slenderness Limit, crit - analysis Sle n de rn e ss Lim it,

crit-

Equ a tio n 6

'

'

crit = 2 1

2 '

, '

60 (1 ) 20

(1 0.06 ) crit

h rup cc

coco

e e D e

f f

+ =

+

FAILURE OF AN FRP-CONFINED RECTANGULAR SPECIMEN

EFFECT OF SECTION SHAPE ON THE EFFECTIVENESS OF CONFINEMENT

Section shapes

,(1 0.06 )h rupcccocof

+

FINITE ELEMENT MODELLING OF FRP-CONFINED CONCRETE IN A SQUARE SECTION USING A MODIFIED

PLASTIC-DAMAGE MODEL

2 1

2 '

'

60 (1 ) 20

crit

e e D e

f

+ =

Distribution of axial stresses

Confinement-dependent damage parameter, hardening rule, and flow rule

Pressure-dependent yield criterion

Unique properties of non-uniformly confined concrete included

kIJF += 1 ' 2

Eqn 1:

SHAPE MODIFICATION

2a 2b

(a) without rounding (b) with rounding

FAILURE OF FRP-CONFINED ELLIPTICAL SPECIMENS

Axi

al s

tress

c (

MP

a)

STRESS-STRAIN MODEL FOR FRP-CONFINED CONCRETE

UNDER CYCLIC COMPRESSION 90

f'co = 38.9 MPa Cyclic (test)

70

80 Efrp = 246817 MPa h,rup = 0.0123 t =0.33 mm

Envelope (Lam & Teng) Cyclic (proposed)

60 R = 76 mm

50

40

30

20

10

0 0 0.005 0.01 0.015 0.02 0.025

Axial strain c

Prediction of the entire stress-strain history

-

RETROFIT OF RC STRUCTURES FOR SEISMIC RESISTANCE

-600

-300

0

300

600

-90 45 0 45 90 (mm)

P (k

N)

T est(C5)

Predicted

Columns: better design procedures Beam-column joints Shear walls Structural systems Performance-based retrofit design

OPTIMAL PERFORMANCE-BASED DESIGN OF SEISMIC RETROFIT MEASURES

Roof Displacement

Bas

e S

hear

Plastic Hinge Rigid Zone

Elastic element

All inelastic behaviour is taken to be lumped into the plastic hinges.

Moment hinges for beams and axial-moment hinges for columns

Pushover analysis is a static nonlinear analysis procedure in which a predefined pattern of earthquake loads is applied incrementally on the structure until a plastic collapse mechanism is reached.

ILLUSTRAVE EXAMPLE

Columns: 1st~ 3rd floors: 0.45m*0.45m; 4th~7th floors: 0.40m*0.40m.

Beams: 0.25m*0.5m

Moment hinges for beams, Axial moment hinges for columns

3.6*

7=25

.2m

30kN/m

0.56

1.92

3.66

5.72

7.90

10.12

12.32

5m 5m 5m

Steel ratios: 0.3% for columns; 1.2% for beams.

0

50

100

150

200

250

300

350

400

450

500

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Top displacement (m)

Bas

e sh

ear (

kN)

Run 1: t=0 Run 2: t=0.165 Run 3: t=0.495 Run 4: t=0.875

3.6*

7=25

.2m

30kN/m

0.56

1.92

3.66

5.72

7.90

10.12

12.32

5m 5m 5m

tfrp=0.165, 0.495, 0.875 mm

Column sway mechanism Beam sway mechanism

I O L S C P

M

A

C B BIOLSCP

C

Without FRP With FRP, t=0.165mm

Column sway mechanism Beam sway mechanism

t=0.495mm

41 hinges

50 hinges

NSMR NEAR SURFACE MOUNTED REINFORCEMENT

Cut a groove

Fill halfway with adhesive

Place FRP into groove

Fill with more adhesive

Level the surface

concrete

groove

FRP bar

adhesive

FRP strip

adhesive

DETAILS OF THE BEAM

TEST BEAMS

8*2229002150*300B2900

8*2218002150*300B1800

8*2212002150*300B1200

8*225002150*300B500

8*22-----2150*300B0

groove width*depth

(mm)

Bond length (mm)

No. of strips Width*height (mm)

Specimen

RC BEAM STRENGTHENED WITH NSM CFRP STRIPS

LOAD-DEFLECTION CURVES

Mid span deflection under loads

-20

0

20

40

60

80

100

120

-20 0 20 40 60 80

mid-span deflection(mm)

tota

l loa

d(kN

)

B0

B500

B1200

B1800

B2900

LONG-TERM MONITORING USING FIBER-OPTIC SENSORS

grating region Cladding

Protective coating

9um 125um 250um

Core

Dimensions of optical fibres

LONG-TERM MONITORING USING FIBER-OPTIC SENSORS

Input light Reflected light Transmitted light

Basic principle of FBG sensors

PULTRUSION OF SMART FRP BARS

Resin Spool

Heating Die Roller

Dry Fiber

FRP Bar

Optic fiber

Optic fiberGlass fiber

EMBEDMENT OF OPTIC FIBERS

SMART FRP BARS

ACKNOWLEDGEMENTS The work presented here has been financially supported by the Hong KongResearch Grants Council, The Hong KongPolytechnic University, and the NationalNatural Science Foundation of China via a national key research project on FRPcomposites in construction.

Thanks are also due to members of myresearch group and many external collaborators.

THANK YOU FOR YOUR ATTENTION!

REPAIR METHODS FOR STEEL BRIDGE PIERS

Courtesy of Dr HB Ge, Nagoya University

SEISMIC RETROFIT OF STEEL TUBES BY FRP JACKETING

Elephant Foot Failure in an Unconfined Tube

Failure Modes of FRP-Confined Tubes

Axial stress-axial strain curves

0

100

200

300

400

0 0.015 0.03 0.045 0.06 Norminal Axial Strain

Axial

Stre

ss (N

/mm2 )

Bare Steel Tube

Single-ply FRP Jacket

Two-ply FRP Jacket

Three-ply FRP Jacket

SEISMIC RETROFIT OF STEEL TUBES BY FRP JACKETING

FINITE ELEMENT MODELING OF FRP-CONFINED STEEL TUBES

0 2 4 6 8 10 12 14 0

200

400

600

800

Axi

al lo

ad (k

N)

Axial shortening (mm)

Explicit overlap Smeared overlap Experiment

Rt

Deformed shapes shown in Fig. 16(b)

Rt

n = 2 w0 = 0.01 mm L = L cr =1.728

STEEL TUBE CONFINED BY A TWO-PLY FRP JACKET

FAILURE MODE OF FRP-CONFINED CONCRETE-FILLED STEEL TUBES, D/t=60

Rupture of FRP Jacekt

AXIAL LOAD-STRAIN CURVES OF FRP-CONFINED CONCRETE-FILLED STEEL TUBES, D/t=60

0

500

1000

1500

2000

2500

0 0.01 0.02 0.03 0.04 0.05

Nominal Axial Strain

Axi

al L

oad

(kN

)

Concrol Specimen

1-ply FRP Jacket

2-ply FRP Jacket

3-ply FRP Jacket

AXIAL LOAD-SHORTENING CURVES: THEORETICAL VERSUS TEST RESULTS

FRP-confined concrete-filled steel tubes

FAILURE MODE OF FRP-CONFINED CONCRETE-FILLED STEEL TUBES, D/t =101

3-ply

BCFT

AXIAL LOAD-SHORTENING CURVES, D/t = 101

3000 FRP rupture

3-ply 2500

) Nk 2000 (d 2-ply a 1-ply 1500

l lo

iaxA 1000 BCFT

500

0 0 5 10 15

Axial deflection (mm)

LOCAL BUCKLING IN CYLINDRICAL SHELLS

Elephants Foot Buckling Real Elephants Foot

50

LOAD-AXIAL SHORTENING CURVES OF PRESSURIZED THIN CYLINDRICAL SHELLS UNDER AXIAL LOAD

0 10 20 30 40 0

5

10

15

20

25

30

Axi

al st

ress

(MPa

)

Axial shortening (mm)

No FRP jacket With system I With system II With system III

Deformed shapes shown in Fig. 18

CFRP rupture

(a) No FRP jacket (b) With system I (c) With system II (d) With system III

STRENGTHENING OF STEEL-CONCRETE COMPOSITE BEAMS

CFRP strips

steel beam

rebars concrete desk

CFRP strips steel section staggered shear studs

concrete deck slab

STRENGTHNING OF STEEL BEAMS Failure Modes

Top flange local buckling

Unstrengthened section failure

Web failure buckling or yielding

In-plane bending failure (material failure) Lateral buckling Debonding at the plate ends Yielding-induced debonding Local buckling of the compression flange Local buckling of the web

FLEXURAL STRENGTHNING OF STEEL BEAMS Failure Modes

Adhesive/steel interface debondingAdhesion failure

Cohesive failureAdhesive layer failure

FRP/adhesive interface debonding FRP rupture FRP delaminationAdhesion failure

FLEXURAL STRENGTHNING OF STEEL BEAMS In-plane failure

Neutral axis

f y

Elastic region

f y

Section analysis z Yielding of steel section z Failure by rupture of FRP

FLEXURAL STRENGTHNING OF STEEL BEAMS Lateral buckling prediction: full-span strengthening

Bonded plate

Steel beam

Adhesive

(1-2 ) LL L

( ) 2 22

1 2 3 2 32 21s y s

cr x x y s

E I I G JL M C C a C C a CL I E I

= + + + + +

yP

y

L/2

q

Load case 1C 2C 3C

Concentrated load at mid-span 1.35 0.55 0.40

Uniformly distributed loads 1.13 0.46 0.53

RAPID STRENGTHENING USING PREPREGS AND FILM ADHEISVE

1. Cutting to size and bonding 2. Ready for curing

Rubber heater

To vacuum pump

3. Curing

Rubber heater

Springs

4. After curing

STRENGTHENING TO ENHANCE LOCAL BEARING RESISTANCE

RHS Web CFRP

Plastic hinge

BOND BEHAVIOUR BETWEEN STEEL

AND CFRP

StStStrainrainrain 355355355355 gaugegaugegauge

PPPP 555555000000555555252525252525252525252525252525252525252525252525252525252525252525252525252525252525505050505050505050505050505050505050505050

CFCFRRPP AdhAdheessiivvee plplatatee

1212 ttaa ttpp

33

StSteeleel tubetube

118118

112

112

StSteel pleel plateate

BOND BEHAVIOUR BETWEEN STEEL AND CFRP

BOND-SLIP MODEL FOR STEEL-CFRP INTERFACES

(1, f)

(f, 0)(0,0)

Slip (mm)

Shea

r stre

ss (M

Pa)

Area under the curve = Gf

Softening Region Debonding Elastic

HYBRID FRP-CONCRETE-STEEL DOUBLE-SKIN TUBULAR COLUMNS

FRP-concrete-steel tubular members

FRP tube

Steel tube

Concrete

FRP tube

Steel tube

(d)

Concrete

(a) (b)

(c)

Concrete

(a) (b)

(c)

Stay-in-place forms for concrete beams, columns and slabs with or without internal reinforcement

FRP + aluminum FRP + timber FRP + more than one other

material: FRP-concrete-steel double-skin

tubes proposed by JG Teng FRP-confined concrete-filled steel

tubes proposed by Y Xiao

INNOVATIOVE COMBINATION OF FRP AND TRADITIONAL MATERIALS FOR OPTIMUM

STRUCTURES


Comparison with a hollow RC column

Hollow section RC columns are widely used as bridge columns and towers. For example, the two main towers of the Stonecutters Bridge reach a height of 300 metres and have a circular hollow section, with a 118 meter high stainless steel skin for the top part of the tower.


Comparison with a hollow RC column

ACKNOWLEDGEMENTS The work presented here has been financially supported by the Hong KongResearch Grants Council, The Hong KongPolytechnic University, and the NationalNatural Science Foundation of China via a national key research project on FRPcomposites in construction.

Thanks are also due to members of myresearch group and many external collaborators.

THANK YOU FOR YOUR ATTENTION!

Structure BookmarksJin-Guang Teng, BEng, PhD, FHKIE Chair Professor of Structural Engineering The Hong Kong Polytechnic University Behavior, Design and Monitoring of Concrete Structures Strengthened with Fibre-Reinforced Polymer (FRP) Composites OUTLINE OF THE PRESENTATION Introduction Bond behaviour between FRP and concrete Flexural strengthening of beams Shear strengthening of beams Strengthening of columns Seismic retrofit Near surface mounted FRP reinforcement Monitoring and other research at PolyU SOME BASIC FACTS OF FRP COMPOSITES Classification Based on Fibre Types GFRP = Glass Fibre-Reinforced Polymer/Plastic CFRP = Carbon Fibre-Reinforced Polymer/Plastic AFRP = Aramid Fibre-Reinforced Polymer/Plastic Forming Methods Prefabrication, Particularly Pultrusion Better Quality Control Wet Lay-Up Using Fibre/Woven Fabric Sheets Greater Flexibility Woven Glass Fabric for Wet Lay-Up Applications Carbon Fibre Sheet for Wet Lay-Up Applications CFRP Pultruded Plate FRP bars Bridge deck Concrete-filled FRP tube OTHER FRP PRODUCTS/APPLICATIONS FRP COMPOSITES IN CONSTRUCTION: EXISTING RESEARCH The majority of published research isstill concerned with FRP strengtheningof concrete structures Hybrid structures of FRP and concrete(or another traditional material) are attractive In terms of new construction, FRP composites are particularly promisingfor new bridges FRP REINFORCING BARS Top Mat for Bridge Decks: FRP Bars from Hughes Brothers Replace steel bars in corrosive environments Courtesy of Prof A Mufti, University of Manitoba MANITOBA FLOODWAY PROJECT STEEL-FREE CONSTRUCTION Because of ISIS Canadas research and influence, the 6 new highway bridges overthe Winnipeg Floodway will have GFRPs in the decks (45,000 square metres). Some ofthese bridges will also have SHM. This is a mega project estimated to cost$700 million, and is therefore, comparableto the one billion dollar Confederation Bridge project completed in 1995. (Courtesy of Prof Mufti) FRP IN CONCRETE STRUCTURES: GROWTH OF SCI PAPERS SINCE 1990 Results from a keyword search using FRP and concrete 0 3 6 4 7 11 16 18 26 32 56 83 93 117119 134 197 227 0 50 100 150 200 250 199019911992199319941995199619971998199920002001200220032004200520062007 Year Number of SCI papers FRP STRENGTHENING OF STRUCTURES Strengthening of RC members: flexural,shear and confinement Retrofit of RC structures for seismic and blast resistance Strengthening of steel, masonry andtimber structures Use of pre-stressed and hybrid FRP OUTLINE OF THE PRESENTATION Introduction 9FRP strengthening of RC Structures Bond behaviour between FRP and concrete Flexural strengthening of beams Shear strengthening of beams Strengthening of columns Seismic retrofit Near surface mounted FRP reinforcement Monitoring and other research at PolyU FRP STRENGTHENING OF RC STRUCTURES: EXAMPLE PRACTICAL APPLICATIONS Flexural Strengthening of a highway RC bridge slab Flexural Strengthening of a two-way slab in a building Strengthening a circular column Strengthening of a water pumping station Courtesy of Prof LP Ye, Tsinghua University FRP STRENGTHENING OF RC STRUCTURES: EXAMPLE LABORATORY TESTS FRP STRENGTHENING OF RC STRUCTURES: RESEARCH PRIOR TO 2002 Concrete Society(2000, 2004) fib (2001) ISIS (2001) JSCE (2001) ACI 440 (2002) More afterwards Design guidelines forexternally bondedFRP reinforcement for strengtheningconcrete structures CHINESE TECHNICAL SPECIFICATIONS NERCProduction and quality control of adhesives Specification of Adhesives used for Construction Strengthening NERCProduction and quality control of laminated CFRP Specification of Carbon Fiber Polymer used for Construction Strengthening NERCDesign methods for flexural, shear and seismic strengthening Technical Specification for Strengthening Concrete Structures with Carbon Fiber Reinforced Polymer Coordinator Scope of applicationTitle of Document Technical Specification for Strengthening Concrete Structures with Carbon Fiber Reinforced Polymer NATIONAL STANDARD A national standard of China for the structural use of FRP composites in construction has been under development since 2002. The standard is now nearing completion. Topics covered by this standard include: 9FRP materials 9Strengthening of RC structures 9Strengthening of masonry structures 9Concrete beams reinforced or prestressed with FRP 9FRP-concrete hybrid structures FigureFigureWHY FRP COMPOSITES? ADVANTAGES: Have All the Advantages of Steel Plates for Plate Bonding Speedy application; Minimal increases in structural weight and size. High Strength/Weight Ratio Lifting equipment eliminated; Reduced labour cost. Flexibility in Shape Can be handled in rolls; easy for wrapping on curved surfaces and around columns. High Resistance to Corrosion and Other Chemical Attacks Durable performance. WHY FRP COMPOSITES? DISADVANTAGES: High material cost Lack of ductility Poor fire resistance Overall: Cost-effective retrofit solutions TYPICAL STRESS-STRAIN CURVES OF FRP COMPOSITES AND STEEL 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 500 1000 1500 2000 2500 3000 Mild steel GFRP Stress (MPa) Strain (%) CFRP OUTLINE OF THE PRESENTATION Introduction Bond behaviour between FRP and concrete Flexural strengthening of beams Shear strengthening of beams Strengthening of columns Seismic retrofit Near surface mounted FRP reinforcement Monitoring and other research at PolyU BOND STRENGTH BY SINGLE-SHEAR PULL-OFF TEST lfrp=95mm DEBONDING FAILURE BEHAVIOUR OF BONDED JOINTS Failure generally occurs in the concrete adjacent to the adhesive-to-concrete interface An increase of bond length L may not increase the bond strength. Tensile strength of plate may not be reached at failure. Bonded plate Concrete P L CHEN AND TENGS BOND STRENGTH MODEL: EQUATIONS Modified from a nonlinear fracture mechanics model: Pu =0.427pL fc' bpLe Le = Eptp fc ' , L = 1 if L Le sin L 2Le if L < Le p = 2 bp/bc 1 + bp/bc P L bp bc OUTLINE OF THE PRESENTATION Introduction Bond behaviour between FRP and concrete Flexural strengthening of beams Shear strengthening of beams Strengthening of columns Seismic retrofit Near surface mounted FRP reinforcement Monitoring and other research at PolyU FLEXURAL STRENGTHENING OF BEAMS RC beam Soffit plate Adhesive layer A Section A FigureCONVENTIONAL FAILURE MODES OF RC FigureBEAMS BONDED WITH AN FRP SOFFIT PLATE FigureFigureFigureFigureFigureFigureFigure(a) FRP rupture (b) Crushing of compressive concrete Concrete Crushing FRP Rupture DEBONDING FALURES OF FRP-PLATED RC BEAMS: CLASSIFICATION OF MODES Debonding Flexural crack Debonding Critical diagonal crack (a) IC debonding (b) CDC debonding Debonding Debonding Debonding (c) CDC debonding with concrete cover separation (d) Concrete cover separation Debonding Debonding Debonding (e) Concrete cover separation under pure bending (f) Plate end interfacial debonding Intermediate crack debonding: (a) Plate end debonding: (b) to (f) CRITICAL DIAGONAL CRACK (CDC) DEBONDING CDC DEBONDING FOLLOWED BY CONCRETE COVER SEPARATION CONCRETE COVER SEPARATION Concrete Cover Separation CONCRETE COVER SEPARATION: CLOSE-UP Steel tension reinforcement PLATE END INTERFACIAL DEBONDING PREDICTION OF PLATE END DEBONDING FAILURES Pure shear debonding Pure flexural debonding A new debonding strength model based on shear-bending interaction 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 M db,end /M db,f Vdb,end /Vdb,s Ceroni et al. (2001) Fanning and Kelly (2001) Rahimi and Hutchinson (2001) Nardo et al. (2003) Pornpongsaroj and Pimanmas (2003) Smith and Teng (2003) For pure shear debonding force PLATE END FAILURES CAN BE SURPRESSED BY U JACKETS Steel tension reinforcement PREVENTION OF PLATE END FAILURES RC beam Tension face plate Section A-A U Jacket A A How should be U jackets be designed and detailed? INTERMEDIATE CRACK (IC) INDUCED INTERFACIAL DEBONDING Debonding at concrete-to-adhesive interface due to high stresses which originate from a major flexural or flexural-shear crack away from the plate ends INTERMEDIATE CRACK (IC) DEBONDING IN AN FRP-PLATED RC BEAM A better understanding A finite element model for IC debonding A new IC debonding strength model A number of recent studies in collaboration with Tsinghua University have led to OUTLINE OF THE PRESENTATION Introduction Bond behaviour between FRP and concrete Flexural strengthening of beams Shear strengthening of beams Strengthening of columns Seismic retrofit Near surface mounted FRP reinforcement Monitoring and other research at PolyU SHEAR STRENGTHING OF RC BEAMS FRP Bonding Configurations Side bonding U-jacketing Wrapping FRP Reinforcement Distributions Strips Plates/sheets FRP Fibre Orientations: Various Angles METHODS OF SHEAR STRENGTHENING. FRP fibre orientation(s) FRP fibre orientation(s) FRP fibre orientation(s) Bond scheme and notation

h h f h f h f

TR =90 SS90 US90 WS90

TR 0 /AntiAliasGrayImages false /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict > /GrayImageDict > /JPEG2000GrayACSImageDict > /JPEG2000GrayImageDict > /AntiAliasMonoImages false /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict > /AllowPSXObjects false /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputCondition () /PDFXRegistryName (http://www.color.org) /PDFXTrapped /Unknown

/Description >>> setdistillerparams> setpagedevice

behavior, design and monitoring of concrete structures ... 2_jg ten… · behavior, design and...

Documents