towards unified bond modelling for the structural behaviour of gfrp-rc kypros pilakoutas
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Towards Unified Bond Modelling for the Structural Behaviour of GFRP-RC Kypros Pilakoutas Harsha Sooriyaararachchi Maurizio Guadagnini Centre for Cement and Concrete Department of Civil and Structural Engineering, University of Sheffield, Sheffield, United Kingdom. GFRP-RC in Construction. - PowerPoint PPT PresentationTRANSCRIPT
4th November 2005
Towards Unified Bond Modelling for the Structural Behaviour of GFRP-RC
Kypros PilakoutasHarsha Sooriyaararachchi
Maurizio Guadagnini
Centre for Cement and ConcreteDepartment of Civil and Structural Engineering, University of Sheffield,
Sheffield, United Kingdom
4th November 2005
GFRP bars
Use of GFRP for bridge deck construction(Franklin county bridge Virginia)
Stiffness of GFRP compared to Steel
0
200
400
600
800
0 5000 10000 15000
Strain (micro strain)
Str
es
s (
MP
a)
GFRP Bare bar
Steel bare bar
GFRP-RC in Construction
4th November 2005
Outline
• Hierarchy of bond modelling
• Macro level Modelling
• Meso level modelling
• Average bond stress slip relation
• Formulation of bond modelling using strain distribution
• Local bond stress-slip-strain relation
s
4th November 2005
Steel reinforcement FRP reinforcement
Hierarchy of bond Modelling
Macro-level modelling
4th November 2005
Steel reinforcement FRP reinforcement
Macro-level modelling
Hierarchy of bond Modelling
Meso-level modelling
4th November 2005
Steel reinforcement FRP reinforcement
Macro-level modelling
Meso-level modelling
Micro-level modelling
Hierarchy of bond Modelling
4th November 2005
Tension stiffening effect Average Strain
Av
era
ge
Str
es
s
Bare bar response
RC response
Tension stiffening of concrete is defined as: the ability of concrete to carry tension between cracks and provide
extra stiffness for RC in tension.
Macro Level Bond Modelling
4th November 2005
Test results bar stress Vs overall strain Average stress strain behaviour of concrete
0
200
400
600
800
0 5000 10000 15000 20000
Strain (Microstrain)
Str
es
s (
MP
a)
C90/13/150
C50/13/150
13mm Bar
0
0.5
1
1.5
2
2.5
3
3.5
0 5000 10000 15000 20000
Strain (Microstrian)
Str
es
s (
MP
a)
C90/13/150
C50/13/150
Strain Softening Behaviour Concrete
4th November 2005
Reinforced concrete in tension
Typical Test Results
c
f N
N
Strain of the composite specimen at
Strain of the bar at crack
Average Strain
Ave
rag
e S
tres
s
N
f
c
Sta
ge I
Pre
Cra
ckin
g
Sta
ge II
Cra
ck P
rop
agat
ion
Sta
ge III
Po
st C
rack
ing
Response of composite section
Bare bar response
Tension Stiffening Behaviour
4th November 2005
1st crack2nd 3rd
Internally strain gauged bar
0
2000
4000
6000Just before first crack (37 kN)
0
2000
4000
After second crack (43 kN)
0 200 400 600 800 1000 12000
2000
4000
Length along the bar (mm)
Ba
r s
tra
in
( )
After third crack (53 kN)
Strain Distribution while Cracking
Stage I
Stage II
4th November 2005
0 200 400 600 800 1000 12000
1000
2000
3000
4000
5000
6000
7000
510152025303641465156606670 kN
Length along the specimen (mm)
Str
ain
( )
0 200 400 600 800 1000 12000
0.1
0.2
0.3
0.4
0.5
0.6
5152025303641465156606670 kN
Length along the specimen (mm)
Sli
p (
mm
)
Post cracking slip and strain
Stage III
4th November 2005
Typical strain and bond stress distribution between cracks
650 700 750 800 850 900 950 10000
5000
10000
15000
20000
Distance between cracks # 1 & # 2 mm
Ba
rs s
tra
in
( )
35 kN
55 kN75 kN95 kN115 kN135 kN155 kN
35.8 kN
650 700 750 800 850 900 950 1000-15
-10
-5
0
5
10
15
Distance between cracks # 1 & # 2 mm
Bo
nd
str
ess
(MP
a)
55 kN
155 kN
Strain and bond between cracks
4th November 2005
Meso Level Bond Modelling
Direct tension test
Pullout test
Magnified images showing bond failure
4th November 2005
Average Bond Stress Vs. Slip
(a) (d) (b) (c)
0
1
2
3
4
5
6
7
8
9
10
11
12
0 0.5 1 1.5 2 2.5 3 3.5
Slip (mm)
Bo
nd
str
es
s (
MP
a)
19-45-5D - Loaded end
19-45-5D - Free end
Comparison of average bond stress slip behaviour for the two test in almost identical circumstances
0 0.5 1 1.5 2 2.5
0
1
2
3
4
5
6
7
8
9
10
11
12
a (0~150)
(b) (175~325)(d) (900~1050)
(d) (750~900)
(d) (750~900) (d) (750~900)
(c) (750~900)(a) (0~175)
Slip (mm)
Bo
nd
Str
ess
(N/m
m2 )
50%
4th November 2005
Stress Conditions During Testing
Direct tension test
Pull out test
4th November 2005
Bond Stress based on strain distribution
dxd
4dE fff
x
0 f dxs 115.2 kN
135.6 kN
155.7 kN
dxd
4dE fff
dxd f
x
0 f dxs
Str
ain
Distance between cracks
2262
2473
2677
2874
3079
3267
dxd
4dE fff
dxd f
free
x
0 f sdxs
Str
ain
Distance along the embedment length
4th November 2005
Local Bond Stress Slip Relationship
0 50 100 1500
5000
10000
15000
Distance from centre of the crack (mm)
Str
ian
( )
0 0.5 1 1.5 2
0
2
4
6
8
10
12
0
25
50
75100
125
150
175
Slip (mm)
Bo
nd
str
ess
(N
/mm2 )
0 50 100 1500
5000
10000
15000
Distance from centre of the crack (mm)
Str
ain
( )
0 0.5 1 1.5
0
2
4
6
8
10
12
12.5
37.5
62.587.5
112.5
137.5
Slip (mm)
Bo
nd
str
ess
(N
/mm
2 )
0 25 50 75 100
150
175
125
0 25 50 75 100
150
125
4th November 2005
0 50 100 1500
5000
10000
15000
Distance from centre of the crack (mm)
Str
ain
( )
dxd
4dE fff
dxd f
x
0 f dxs
x
f
0 0.1 0.2 0.3 0.4 0.5 0.60
2
4
6
8
10
*8474
940610464
1130312317
13241 14159
Different Slip at (mm)D
iffe
ren
t b
on
d s
tre
ss (
N/m
m2)
*f
f
s
4th November 2005
0 0.5 1 1.50
2
4
6
8
10
352
1196
2071
310039144854 5740
665375858474
940610464
1130312317
1324114159
Slip at different strain levels (mm)
Bo
nd
str
ess
(N/m
m2 )
Bond stresses slip at different strain
4th November 2005
0 0.5 1 1.50
1
2
3
4
5
6
7
8
9
10
1196
3100 48546653
847410464
12317
14159
Slip at different strain levels (mm)
Bo
nd
str
es
s (
N/m
m2)
00
e14 25053
.
)()( ..max
S.
1
251.
cal
icalS
Scal= Slip at peak bond stress at calibrated strain
cal = Referred strain for calibration
s Relation for BOND
4th November 2005
0 0.5 1 1.5 2
0
2
4
6
8
10
0
25
25
50
50
7575
100
100
125125
150150
175
175
Local slip (mm)
Lo
cal
bo
nd
str
ess
(N/m
m2 )
Comparison of Results
4th November 2005
Local Bond Stresses in Pull-out 5D
0 20 40 60 80 100
0
1
2
3
4
length (mm)B
on
d s
tre
ss
(
N/m
m2)
0 20 40 60 80 100
0
200
400
600
800
Length (mm)
Str
ain
(
)
0 0.005 0.01 0.015 0.020
0.5
1
1.5
2
2.5
3
91mm
Slip at various section mm
Bo
nd
str
ess
(N
/mm
2)
19mm
38 mm
57 mm
76 mm
95.5mm
0 0.05 0.1 0.15 0.20
2
4
6
8
10
Slip at various sections mmB
on
d s
tre
ss
(N/m
m2)
19 mm
38 mm
57 mm
76 mm
95 mm
0 20 40 60 80 100
0
2
4
6
8
10
Length(mm)
Bo
nd
str
es
s
(N
/mm
2)
0 20 40 60 80 100
0
1000
2000
3000
Length (mm)
Str
ain
(
)
Grade 90
Grade 45
4th November 2005
Local Bond Stresses in Pull-out 10D
0 50 100 150 2000
2
4
6
8
10
12
length(mm)
Bo
nd
str
es
s
(N
/mm
2)
0 0.05 0.1 0.15 0.20
2
4
6
8
10
12
0mm
Slip at various section (mm)B
on
d s
tre
ss
(N/m
m2)
57mm76mm
96 mm
115 mm
134mm
153 mm
172mm
191mm
0 50 100 150 200
0
1000
2000
3000
4000
Length (mm)
Str
ain
(
)
0 50 100 150 2000
1
2
3
4
Length(mm)
Bo
nd
str
es
s
(N
/mm
2)
0 0.02 0.04 0.06 0.080
1
2
3
4
0mm
Slip at various section (mm)
Bo
nd
str
es
s
(N
/mm
2)
38.2mm57.3mm
95mm115 mm
134 mm
153 mm172mm
191mm
0 50 100 150 200
0
500
1000
1500
Length (mm)
Str
ain
(
)
Grade 90
Grade 45
4th November 2005
Comparisons of results
Local bond behaviour in pull out test 19/45/10D
0 0.02 0.04 0.06 0.080
0.5
1
1.5
2
2.5
3
3.5
4
Local slip mm
Bo
nd
str
ess
(N/m
m2 )
19.1 mm19 mm
57 mm57 mm
96 mm
96 mm
115 mm115 mm
134 mm
134 mm
153 mm
153 mm
171 mm171mm
191 mm
191mm
4th November 2005
Conclusions
• -s- approach proposed
• Is Average bond stress slip relationship useful?
• Different levels of bond modelling
• More work to be done
• Bond stress profile changes with increasing load
• Testing conditions affect bond behaviour