FRP-Reinforced Glulam Bridges: Development and ......Can we build beams with low-quality, cheap...
Transcript of FRP-Reinforced Glulam Bridges: Development and ......Can we build beams with low-quality, cheap...
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FRP-Reinforced Glulam Bridges: Development and Implementation
Prof. Bill Davids, Prof. Habib Dagher, Dr. Robert Lindyberg, Prof. Roberto Lopez-Anido
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FRP-Reinforced Glulam
• Low grades stronger in compression• Reinforced concrete analogy – by using FRP as
tension reinforcement, we mitigate tension failure
Tension
Compression
Can we build beams with low-quality, cheap laminations and a small amount of FRP that are stronger than beams with high-
grade tension laminations?
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FRP-Reinforced Glulam BeamsStrength model and beam strength testing
(H. Dagher and R. Lindyberg)
Wood-FRP bond integrity(H. Dagher, R. Lopez-Anido, B. Goodell, D. Gardner, Y. Hong, B. Herzog, L. Muszyński, C. Tascioglu)
Bridge girder fatigue behavior(W. Davids, M. Richie)
Demonstration structures(H. Dagher, W. Davids, R. Lindyberg, R.Lopez-Anido)
AASHTO design specifications
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FRP-Glulam Strength and Ductility
130mm x 305mm x 6.4m span
0
100kN
0 250mm
CONTROL:MOR=27.7MPa
1% GRP:MOR=49.9MPa
3% GRP:MOR=65.3MPa
Mid-Span Displacement
Load
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FRPUTS, E (mean, COV, PDF)
Lamstock- UTS, UCS, E
(mean, COV, PDF)- 3x3 correlation matrix
strain
stre
ss
Bending Strength Prediction
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Moment-Curvature Analysis
N.A.
εc
ε(y) σ(y)
fyield
C
T
Φ
∑ ∫∑ ∫
=
=⇒=
ydAM
dAF
σ
σ 00 Gives NA location
Gives M corresponding to Φ
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• M-Φ simulations repeated many times for different randomly generated cross-sections
• Result is the CDF of beam MOR and MOE• Allowable Bending Stress Fb= 5%LTL MOR/2.1
0.00
0.20
0.40
0.60
0.80
1.00
34 62MOR (MPa)
Cum
ulat
ive
Dis
trib
utio
n
5% LTL MOR
Monte Carlo Simulation
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Beam 37-B-3
MOR = 46.9 MPa
FRP-Glulam Testing(11m span – 1.2% GFRP)
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Validation of Analyses 279 Beam Tests
Test Series Sample size Difference5th Fb
6.4m 90 1 %11.0m 66 4 %15.2m
2.9m- 19.5m4875
7 %5 %
5th
0.00
0.20
0.40
0.60
0.80
1.00
5000 6000 7000 8000 9000
b
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0
0.2
0.4
0.6
0.8
1
1.2
V = b x d x l
Cv
CV = (1291.5/V) 0.1
2%
130mm x 305mm x 6.4m span
273mm x 1370mm x 30.5m
0%
1%
Volume Effect
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wood expands and contracts
FRP
Wood-FRP Bond IntegrityHygrothermal Effects are #1 Durability Issue
Wood-FRP InterfaceStresses
Stressconcentration
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Screening Study: Nine FRP/Adhesive Systems ASTM D2559: 4 of 9 Passed: 4 of 9 Passed
E-glass vinyl ester
Resin infusion
Fabric reinforcement bound and bonded by SCRIMP
E-glass urethane pultrusionPre-consolidated sheet bonded w/ urethane
E-glass epoxycontinuous lamination
Pre-consolidated sheet bonded w/ epoxy
Carbon vinyl ester
Resin infusion
Fabric reinforcement bound and bonded by SCRIMP
Material Fiber type
Polymer matrix
FRP fabrication
Bonding process
A
B
C
D
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Fatigue Testing
• Eighteen 6.1m-span specimens loaded in 4-point bending
• Fatigued for 2 million cycles at 2Hz
• Loading to 81% of Fv concurrently with 1.5Fb
• Stress ratio fixed at 0.33
• Daily static load tests
• Loaded to failure post-fatigue to quantify residual strength
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Compression failure(post-fatigue)
• 14 of 18 specimens failed in tension• Two shear failures, two compression failures
Shear failure(post-fatigue)
Fatigue Testing Results
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• Glulams with full-length reinforcing are not prone to fatigue failures– Potential for compression and shear failures at
higher reinforcement ratios– Significant delaminations between wood and
FRP can be tolerated in high shear regions
Fatigue Testing Results
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Fairfield Bridge70’ span FRP-glulam with composite concrete deck
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Milbridge PierMultiple-span FRP-reinforced glulam deck panels
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Specification DevelopmentASTM D7199-07: Standard Practice for Establishing Characteristic Values for Reinforced Glued Laminated Timber (Glulam) Beams Using Mechanics-Based Models
• Passed in 2007
• Contains provisions for establishing FRP-glulam strength
• Methods based on moment-curvature analysis and Monte-Carlo simulation described earlier in presentation
• References ASTM D2559 for assessment of wood-FRP bond durability
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Specification DevelopmentAASHTO LRFD Bridge Design Specifications
• Section 8, various articles• 8.4.1.3 Tension-Reinforced Glulams defined
– Type and amount of reinforcement– Design values determined via ASTM D7199
• Modification to adjustment factors– 8.4.4.5 Volume factor – no reduction in Fb
– 8.4.4.3 Wet service factor– 8.4.4.2 Format conversion factor (ASD – LRFD)
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Specification DevelopmentAASHTO LRFD Bridge Design Specifications
Philosophy:
• Design engineer specs a value for Fb and beam dimensions
• Laminator designs layup using ASTM D7199 provisions
• Lamstock species, grade, and layup may be varied
• FRP reinforcement type and percentage refined
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Sample AASHTO Design Calcs• Douglas fir L1-L2 layup (low grade laminations)
• Size beam for 56’ span bridge girders spaced at 4’-6”
• Reinforcing scenarios: 0%, 1%, 2% and 3% FRP
FRP Percentage
Fb(psi)
E(msi)
Beam depth(in)
Beam Width(in)
0% 1500 1.44 66 6.751% 2600 1.57 53 6.752% 3400 1.68 46 6.753% 3800 1.78 45 6.75
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Conclusions
• Over a decade of research is bearing fruit
• Specifications capture results of research findings
• Ongoing collaboration between industry, the APA and UMaine to deliver FRP-glulam to market
• Economics of FRP-glulam are being studied
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Acknowledgments
• The FHWA (program manager S. Duwadi)• The National Science Foundation• The USDA• The MaineDOT• APA - The Engineered Wood Association