1
Bridge Deck Research at Villanova University
Fatigue and Serviceability of
GFRP Reinforced Bridge
Decks Designed by Traditional
and Empirical Methodologies
Presented at the 2015 AASHTO SCOBS T6 Committee Meeting,
Saratoga Springs, NY
Villanova Faculty
Joseph Robert Yost (corresponding: [email protected]),
David Dinehart, Shawn Gross
2
Two full scale bridge decks, each -
• 33 ft. – 6 in. by 8 ft.
• AASHTO TYPE II support
• Girder spacing = 9 ft. x 3
• Fascia overhang = 3 ft. 3 in.
• 8 in. thick deck
• 3 in. haunch with shear reinforcement
• Fatigue loaded for critical M+ and M- load cases with 2,000,000 load cycles/load case
South half (TDM)
North half (EDM)
33 ft. - 6 in.
Deck thickness = 8 in.
AASHTO Type II support (typ.) 3 ft. - 3 in. (typ.)
Full parapet (typ.)
3 equal spaces at 9 ft. = 27 ft.
Research Scope
South North
GFRP
Reinforced
AASHTO
TraditionalCSA Empirical
Steel
Reinforced
AASHTO
Traditional
AASHTO
Empirical
DeckDesign Method
3
1. Research Scope
2. Sample Fabrication and Material Properties
3. Load Cases and Design Methodology
4. Experimental Details
5. Test Results
6. Conclusions and Findings
Presentation Overview
4
Sample Fabrication
Supporting Beams Poured First
Parapets poured last Finished samples
Deck poured next (GFRP reinforced deck shown)
5
Str
ess
Strain
Steel: Elatic-plastic
GFRP: Elastic-brittle
Material Properties
• GFRP supplier – Hughes Brothers
• Epoxy coated steel rebar
• Concrete
• Supplier – JDM Materials
• PennDOT Class AAA
• 1 truck per deck
• Poured on same day
Steel GFRP Concrete
Fy or Fu (ksi)
Es or Ef (ksi)
f'c (ksi)
Steel
Reinforced60 29,000 7.6
GFRP
Reinforced105 6,700 5.8
Deck Sample
6
• Tensile strengths 1.5 to 2 times as great as Grade 60 steel • 25% the weight of steel • Modulus about 25% of steel • Impervious to Chlorides and low pH chemicals
Nominal Area Tensile Strength Modulus of Elasticity
(in2) (ksi) (ksi)
Steel #5 0.307 60 29,000
GFRP #5 0.307 105 6,700
Bar SizeMaterial
Hughes Brothers Aslan 100 FRP
• Manufactured through a pultrusion process
• Sand-coated and helically wrapped to increase bond
• Brittle behavior leads to over-reinforced design
• Design guides published by : o American Concrete Institute (ACI)
o American Association of State Highway and Transportation Officials (AASHTO)
o Canadian Standards Association (CSA)
Properties of Glass Fiber Reinforced Polymer (GFRP) Rebar
7
1. Research Scope
2. Sample Fabrication and Material Properties
3. Load Cases and Design Methodology
4. Experimental Details
5. Test Results
6. Conclusions and Findings
7. Future Research
Presentation Overview
8
Pservice = PLL {m} {IM} where, PLL = HS25 Truck Load = 20 kips/wheel or 40 kips/axle m = multiple presence factor = 1.2 for 1 lane loaded IM = impact factor = 1.33 Pservice = 64 kips/axle
The service load used for testing was based on HS25 loading and calculated as follows:
32 k 32 k
Service Limit State
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Positive bending (MP-TR)
Negative bending (MN-TR)
Positive bending (MP-EM)
Negative bending (MN-EM)
Each for
GFRP Reinforced Deck
Steel Reinforced Deck
Traditional Design
(South half)
Empirical Design
North half)
Load Case Summary
Traditional Design Empirical Design
Negative Traditional
Positive Empirical
Negative Empirical
Positive Traditional
3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 1.5 ft 1.5 ft
South North
MP-EM
MN-EM
MP-TR
MN-TR
The deck was subjected to four (4) load cases
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GFRP Reinforced Deck Design
AASHTO Traditional Design
• LRFD Bridge Design Guide Specifications for GFRP-Reinforced Concrete Bridge Decks and Railings (AASHTO 2009)
• Based on strength fMn > Mu using Equivalent Strip (ES)
• Overreinforced for flexure
• Cracking width: w ≤ 0.02 in. (Art. 2.9.3.4)
• Concrete stress: fc ≤ 0.45 f’c (Art. 2.9.3.6)
• Deflection: D ≤ L/1000 (Art. 2.7.2)
CSA Empirical Design
• Design recognizes arching action
• Canadian Standards Association (CSA) Empirical Design Published in Clause 16.8.8.1 of Canadian Highway Bridge Design Code (CSA, 2006)
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AASHTO Strength (Traditional) Design
• Based on flexural strength fMn > Mu
• Underreinforced for flexure
• Designing using Equivalent Strip (ES)
• PennDOT modifications
AASHTO Empirical Design
• Design recognizes arching action
• Failure punching shear
• Composite, cast-in-place, other
• 0.27in2/ft. in bottom layers (#5@12”)
• 0.18 in2/ft. in top layers (#4@12”)
Steel Reinforced Deck Design
12
Reinforcement Summary
Traditional Design Empirical Design
Transverse bars
Longitudinal bars
bottom bars
top bars
Top clear cover 2.5" steel
1.0" GFRP
Bottom cover 1.0" steel
1.0" GFRP
Negative Traditional
Positive Empirical
Negative Empirical
Positive Traditional
3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 1.5 ft 1.5 ft
(# at in.) (in2 / ft) (# at in.) (in
2 / ft) (# at in.) (in
2 / ft) (# at in.) (in
2 / ft) (in
2 / ft
2)
Strength#5 at
5.5"0.67 #5 at 6" 0.61 #4 at 12" 0.20 #5 at 9" 0.41 1.89
Empirical #4 at 12" 0.20 #5 at 12" 0.31 #4 at 12" 0.20 #5 at 12" 0.31 1.01
Ratio (E/S) 0.29 0.50 1.00 0.75 0.53
Strength #5 at 4" 0.92 #5 at 4" 0.92 #5 at 10" 0.37 #5 at 5" 0.74 2.95
Empirical #5 at 12" 0.31 #5 at 4" 0.92 #5 at 12" 0.31 #5 at 12" 0.31 1.84
Ratio (E/S) 0.33 1.00 0.83 0.42 0.63
Steel
GFRP
Design
Transverse Longitudinal
Total
Top BottomTop BottomMaterial
South North
MP-EM
MN-EM
MP-TR
MN-TR
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1. Research Scope
2. Sample Fabrication and Material Properties
3. Load Cases and Design Methodology
4. Experimental Details
5. Test Results
6. Conclusions and Findings
7. Future Research
Presentation Overview
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Instrumentation Plan
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Pretest Phase - Crack deck
Overload Phase - Stabilize deck
Fatigue Phase 1 - 1,000,000 cycles/load-case at fatigue limit state
Fatigue Phase 2 - 1,000,000 cycles/load-case at service limit state
Load Schedule
For each load phase, four load cases were applied and sequenced as:
1) Negative Bending Traditional (MN-TR)
2) Negative Bending Empirical (MN-EM)
3) Positive Bending Traditional (MP-TR)
4) Positive Bending Empirical (MP-EM)
Conclusion – each deck loaded in total by 8 million cycles
64 k
Pretest phase
(PTP)
Lo
ad
Time
80 k
36 k
60 k
2 C
ycl
es
100
Cycl
es
1 k
1 Million
Cycles
Overload phase
(OLP)
Fatigue Phase 1 (FP1)
Fatigue Phase 2 (FP2)
1 Million
Cycles
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Pretest and Overload Phases Signal Stabilization
Crack Width on GFRP Deck MN-TR
0
10
20
30
40
50
60
70
80
90
0 0.01 0.02 0.03 0.04
Ap
pli
ed
Lo
ad (
kip
s)
Deflection (in) - LVDT 5
Pretest Phase (PTP)
Overload Phase (OLP)
Last 10 Cycles OLP0
10
20
30
40
50
60
70
80
90
-0.006 -0.005 -0.004 -0.003 -0.002 -0.001 0.000
Ap
pli
ed
Lo
ad (
kip
s)
Crack Width (in) - Pi Gage 2
Pretest Phase (PTP)
Overload Phase (OLP)
Last 10 Cycles OLP
Continued Crack Opening
Initial Crack OpeningStable
Crack Stable Deflection
Results for Crack Width on GFRP Deck; Negative Bending - Traditional Design
Negative Bending
Traditional Design
crack
measurement
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1. Research Scope
2. Sample Fabrication and Material Properties
3. Load Cases and Design Methodology
4. Experimental Details
5. Test Results
6. Conclusions and Findings
7. Future Research
Presentation Overview
18
Serviceability Limits
Deflection (2)
(in) (mm) (in) fc (ksi) ec (me) (4)
GFRP 0.02 0.51 0.108 1.8 (3) 600
(2) L/1000 and L = 9 x 12 in
(3) AASHTO GFRP Art. 2.9.3.6 (2009) f c < .45(f'c = 5.8 ksi) = 2.6 ksi
(4) ec = fc / Ec where Ec = 57 {f'c = 5800 psi}
1/2 ksi
(1) AASHTO GFRP Art 2.9.3.4 (2009)
Material
Allowable Limit
Crack width (1) CC Stress & Strain
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Sequence
Hysteresis at 1 and 2 million cycles with % Allowable at 2M
• Crack width (negative and positive bending)
• Deflection (negative and positive bending)
• Concrete Strain (negative and positive bending)
% Allowable at 2 million - GFRP vs. Steel
• Crack width
• Deflection
• Concrete Strain
Profile Plots
• Deflection
• Concrete strain
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GFRP results at 1 and 2 million cycles Crack Width - Negative Bending
Traditional Design Empirical Design MN-EM MN-TR
crack measurement crack measurement
0
64
-0.02 0.00
Load
(k
)
Crack width (in)
MN-TR 1 million
MN-TR 2 million
MN-EM 1 million
MN-EM 2 million
AASHTO Limit (0.02 in.)
Traditional Empirical
0.3
7
0.7
7
0.0
0.2
0.4
0.6
0.8
1.0
MN-TR MN-EM
Rat
io:
Mea
sure
d/A
llow
able
at
2M
(-)
Load Case
21
GFRP results at 1 and 2 million cycles Crack Width - Positive Bending
Top B ottom Top B ottom
(# atin.) (# atin.) (# atin.) (# atin.)
S treng th # 5at4in. # 5at4in. # 5at10in. # 5at4in.
Empirical # 5at12in. # 5at12in. # 5at12in. # 5at12in.
S treng th # 5at5.5in. # 5at6in. # 4at12in. # 5at9in.
Empirical # 4at12in. # 5at12in. # 4at12in. # 5at12in.
Lo ng itudinalB ars
G FR P
S teel
M aterial Desig n
TransverseB ars
Traditional
Design
Empirical
Design MP-EM MP-TR
crack measurement crack measurement
0
64
-0.02 0.00
Load
(k
)
Crack width (in)
MP-TR 1 million
MP-TR 2 million
MP-EM 1 million
MP-EM 2 million
AASHTO Limit (0.02 in.)
Traditional
Empirical
0.3
1 0.4
1
0.0
0.2
0.4
0.6
0.8
1.0
MP-TR MP-EM
Rat
io:
Mea
sure
d/A
llow
able
at
2M
(-)
Load Case
22
GFRP results at 1 and 2 million cycles Deflection - Negative Bending
Traditional Design Empirical Design MN-EM MN-TR
0
64
0.00 0.12
Lo
ad (
k)
Deflection (in)
MN-TR 1 million
MN-TR 2 million
MN-EM 1 million
MN-EM 2 million
AASHTO Limit (0.108 in.)
Traditional
Empirical
0.4
7 0
.62
0.0
0.2
0.4
0.6
0.8
1.0
MN-TR MN-EM
Rat
io:
Mea
sure
d/A
llow
able
at
2M
(-)
Load Case
23
GFRP results at 1 and 2 million cycles Deflection - Positive Bending
Top B ottom Top B ottom
(# atin.) (# atin.) (# atin.) (# atin.)
S treng th # 5at4in. # 5at4in. # 5at10in. # 5at4in.
Empirical # 5at12in. # 5at12in. # 5at12in. # 5at12in.
S treng th # 5at5.5in. # 5at6in. # 4at12in. # 5at9in.
Empirical # 4at12in. # 5at12in. # 4at12in. # 5at12in.
Lo ng itudinalB ars
G FR P
S teel
M aterial Desig n
TransverseB ars
Traditional
Design
Empirical
Design MP-EM MP-TR
0
64
0.00 0.12
Lo
ad (
k)
Deflection (in)
MP-TR 1 million
MP-TR 2 million
MP-EM 1 million
MP-EM 2 million
AASHTO Limit (0.108 in.)
Traditional
Empirical
0.5
0
0.7
3
0.0
0.2
0.4
0.6
0.8
1.0
MP-TR MP-EM
Rat
io:
Mea
sure
d/A
llow
able
at
2M
(-)
Load Case
24
GFRP results at 1 and 2 million cycles Concrete Strain - Negative Bending
Traditional Design Empirical Design MN-EM MN-TR
0
64
-600 0
Lo
ad (
k)
Critical concrete strain (me)
MN-TR 1 million
MN-TR 2 million
MN-EM 1 million
MN-EM 2 million
Traditional Empirical
AASHTO Limit (600 me)
0.5
0
0.7
4
0.0
0.2
0.4
0.6
0.8
1.0
MN-TR MN-EM
Rat
io:
Mea
sure
d/A
llow
able
at
2M
(-)
Load Case
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GFRP results at 1 and 2 million cycles Concrete Strain - Positive Bending
Top B ottom Top B ottom
(# atin.) (# atin.) (# atin.) (# atin.)
S treng th # 5at4in. # 5at4in. # 5at10in. # 5at4in.
Empirical # 5at12in. # 5at12in. # 5at12in. # 5at12in.
S treng th # 5at5.5in. # 5at6in. # 4at12in. # 5at9in.
Empirical # 4at12in. # 5at12in. # 4at12in. # 5at12in.
Lo ng itudinalB ars
G FR P
S teel
M aterial Desig n
TransverseB ars
Traditional
Design
Empirical
Design MP-EM MP-TR
0
64
-600 0
Lo
ad (
k)
Critical concrete strain (me)
MP-TR 1 million
MP-TR 2 million
MP-EM 1 million
MP-EM 2 million
Traditional
Empirical
AASHTO Limit (600 me)
0.3
7
0.5
8
0.0
0.2
0.4
0.6
0.8
1.0
MP-TR MP-EM
Rat
io:
Mea
sure
d/A
llow
able
at
2M
(-)
Load Case
26
% Allowable - Crack Width GFRP vs. Steel at 2 million cycles
0.5
3
0.4
2
0.5
3
2.0
0
0.3
1
0.4
1
0.3
7
0.7
7
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
MP-TR MP-EM MN-TR MN-EM
Cra
ck-w
idth
Rat
io:
Mea
sure
d/A
llo
wab
le (
-)
Load Case
Steel GFRP
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% Allowable - Deflection GFRP vs. Steel at 2 million cycles
0.7
7
1.1
0
0.5
7
0.9
9
0.5
0
0.7
3
0.4
7
0.6
2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
MP-TR MP-EM MN-TR MN-EM
Def
lect
ion R
atio
: M
easu
red
/All
ow
able
(-)
Load Case
Steel GFRP
28
% Allowable - Concrete Strain GFRP vs. Steel at 2 million cycles
0.6
8
0.7
1
0.3
7
1.4
6
0.3
7
0.5
8
0.5
0
0.7
4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
MP-TR MP-EM MN-TR MN-EM
CC
Str
ess
Rat
io:
Mea
sure
d/A
llo
wab
le (
-)
Load Casee
Steel GFRP
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Profiles at 2 Million Cycles Deflection
-0.0341
-0.0411
0.0038
-0.0342
0.0011
-0.0426 -0.050
-0.040
-0.030
-0.020
-0.010
0.000
0.010
0 9 18 27
Def
lect
ion
(in
)
Deck Width (ft)
Traditional Design: Before
Traditional Design: After
Empirical Design: Before
Empirical Design: After
G1
G2 G3 G4
-0.0249
-0.0233
0.0019
-0.0221
-0.0288
0.0068
-0.0287
-0.0383 -0.045
-0.040
-0.035
-0.030
-0.025
-0.020
-0.015
-0.010
-0.005
0.000
0.005
0.010
0 9 18 27
Def
lect
ion
(in
)
Deck Width (ft)
Traditional Design: Before
Traditional Design: After
Empirical Design: Before
Empirical Design: After
G1 G2 G3
G4
Negative Bending
(MN-TR and MN-EM)
Positive Bending
(MP-TR and MP-EM)
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Negative Bending
(MN-TR and MN-EM)
Positive Bending
(MP-TR and MP-EM)
Profiles at 2 Million Cycles Concrete Strain
-108
-179 -189
-173
-240 -246
-300
-250
-200
-150
-100
-50
0
50
100
0 9 18 27
Co
ncr
ete
Str
ain
(µε)
Deck Width (ft)
Taditional Design: Before
Traditional Design: After
Empirical Design: Before
Empirical Design: After
G1
G2 G3 G4
-140
-186 -177
-242
-300
-250
-200
-150
-100
-50
0
50
100
150
0 9 18 27
Con
cret
e S
trai
n (µε)
Deck Width (ft)
Traditional Design: Before
Traditional Design: After
Empirical Design: Before
Empirical Design: After
G1
G2 G3 G4
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Conclusions and Findings
• For GFRP Traditional Design, Maximum % Allowable After 2 M Cycles
Crack Width = 37%
Deflection = 50%
CC Strain = 50%
• For GFRP Empirical Design, Maximum % Allowable After 2 M Cycles
Crack Width = 77%
Deflection = 73%
CC Strain = 74%
• Signal magnitude and stiffness stable after 2 million load cycles
• In many cases % Allowable for GFRP better than steel for like design (Traditional & Empirical) and like load case (Positive & Negative)
32
Questions?
• For further information please contact
Joseph Robert Yost, Ph.D., PE
Professor, Structural Engineering
Department of Civil and Environmental Engineering
Villanova University
800 Lancaster Avenue, Villanova, PA 19085-1681
Email: [email protected]
Phone/Fax: 610-519-4955/6754