presentation given at ICCS 13

1. 28-05-2013
Challenge the future
Delft
University of
Technology
Prolonging the service life of existing
reinforced concrete slab bridges
through experimental studies on the shear
capacity
Eva Lantsoght, Cor van der Veen, Joost Walraven

2. 2Prolonging the service life of existing reinforced concrete slab bridges
Introduction
Problem Statement
Bridges from 60s and 70s
The Hague in 1959
Increased live loads
common heavy and long truck (600 kN)
End of service life + larger loads

3. 3Prolonging the service life of existing reinforced concrete slab bridges
Introduction
Assessment strategy
Required safety level: Repair level: 3.3 ≤ β ≤ 3.6
=> Research on additional load-bearing mechanisms in
slab bridges

4. 4Prolonging the service life of existing reinforced concrete slab bridges
Introduction
Transverse load redistribution
• Additional dimension in slabs
• Transverse redistribution
capacity
• Direct load transfer to support

5. 5Prolonging the service life of existing reinforced concrete slab bridges
Experiments
Size: 5m x 2.5m (variable) x 0.3m = scale 1:2
Continuous support, Line supports
Concentrated load: vary a/d and position along width

6. 6Prolonging the service life of existing reinforced concrete slab bridges
Code extension proposal
Limit State function
Experiment vs. Design value
• Experiment
• mean values
• Test/Predicted ratio
• Design value
• characteristic values
f d
P P R R
Reliability analysis based on load and resistance

7. 7Prolonging the service life of existing reinforced concrete slab bridges
Code extension proposal
Random variables
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
2
4
6
8
10
12
36 38 40 42 44 46 48 50 52 More
Frequency
fc,cube,mean (MPa)
Frequency
Cumulative %
concrete compressive strengthTest/Predicted

8. 8Prolonging the service life of existing reinforced concrete slab bridges
Code extension proposal
Slabs subjected to Wheel Loads
• Enhancement factor depends on fck
• Experiments: fck not as in shear formula
• Effect of reduced support width
• Proposal for av ≤ 2.5dl
1/3
, , , ,100 1.9
225
ck
Rd c prop Rd c l ck eff red l
f
V C k f b d
, 0.52 0.48
sup
eff red eff
l
b
b
b

9. 9Prolonging the service life of existing reinforced concrete slab bridges
Economics
• Repair cost
• Demolition cost
• Recycling cost
• New construction
Environment
• Impact of repair
• Impact of
replacement
• CO2 emissions
• Materials
• Transport
Social
• Visual impact
• Traffic delays
• Employment
Sustainability

10. 10Prolonging the service life of existing reinforced concrete slab bridges
Impact on Sustainability
Example replacement of 3-span slab
bridge (deck only)
• Economic cost: 500k – 640k €
• Environmental cost: 136 ton CO2
• Blast furnace cement: 74 ton CO2
• Portland slag cement: 122 ton CO2
• Social cost: case-dependent
• can be 9 times economic cost
• Scope: 600 slab bridges

11. 11Prolonging the service life of existing reinforced concrete slab bridges
Summary & Conclusions
1. Safety level “Repair”
2. Prolonging service life = savings
at end-of-life stage
3. Utilize transverse load
redistribution capacity of slabs
4. Code extension proposal
5. Impact is economic,
environmental and social

12. 12Prolonging the service life of existing reinforced concrete slab bridges
Contact:
Eva Lantsoght
E.O.L.Lantsoght@tudelft.nl
+31(0)152787449