practical application of transverse load redistribution in reinforced concrete solid slab bridges
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18-07-2014
Challenge the future
DelftUniversity ofTechnology
Practical applicationof transverse load redistribution in reinforced
concrete solid slab bridges
Eva Lantsoght, Ane de Boer, Cor van der Veen
2Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Overview
•Introduction•Principle of Levels of
Approximation•Experiments•Load spreading method•Consequences•Summary
3Practical application of transverse load redistribution in reinforced concrete solid slab bridges
IntroductionProblem Statement
Bridges from 60s and 70s
The Hague in 1959
Increased live loads
heavy and long truck (600 kN > perm. max = 50ton)
End of service life + larger loads
4Practical application of transverse load redistribution in reinforced concrete solid slab bridges
IntroductionHighway network in the Netherlands
•NL: 60% of bridges built before 1976
•Assessment: shear critical in 600 slab bridges
•LoA I method: Quick Scan
Highways in the Netherlands
5Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Principle of Levels of ApproximationModel Code 2010
•Approach from fib Model Code 2010
•Solution strategy = different levels of approximation
•Eg: Shear capacity in Model Code 2010
6Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Experiments
Size: 5m x 2.5m (variable) x 0.3m = scale 1:2
Continuous support, Line supportsConcentrated load: vary a/d and position along width
7Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingEffective width in shear
45° load spreading - Dutch practice
45° load spreading – French practice
Or: fixed value (eg. 1m = 3.3ft)
8Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingResults of experiments
BS = 0.5m = 1.6 ft wide BX = 2.0m = 6.6ft wide
9Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingResults of experiments
500
0 1000 1500 2000 2500b (mm)
10Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingStatistical analysis
•Calculated from series vs. 45° load spreading
•Comparison between database (literature) + experiments and methods• French load spreading method
underestimates less• Lower COV for French load spreading
method• Database: 63% vs 42%
• Delft experiments: 26% vs 22%
11Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingFinite element results (1)
Models of 1.5m = 4.9ft wide
a = center-to-center distance between load and support
Effective width from shear stress distribution over support
12Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingFinite element results (2)
Models of 2.5m = 8.2ft wide
a = center-to-center distance between load and support
Effective width from shear stress distribution over support
13Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingFinite element results (3)
Models of 3.5m = 11.5ft wide
a = center-to-center distance between load and support
Effective width from shear stress distribution over support
14Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingFinite element results (4)
•French load spreading method gives safe estimate of beff
•NLFEA: beff depends slightly on slab width•NLFEA: influence of a/d less than in French method
•French method sufficient for LoA 1
15Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingApplication to slab bridges (1)
•Loading at edge
•Asymmetric effective width
16Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingApplication to slab bridges (2)
Effective width per axle instead of per wheel print
17Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Load spreadingConsequences
•Larger effective width
•Smaller shear stress
•More economic design
•Sharper assessment
18Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Summary & Conclusions
1. Level I of Assessment: Quick Scan method
2. French load spreading method1. Experimental results2. Statistical analysis3. Finite element results
19Practical application of transverse load redistribution in reinforced concrete solid slab bridges
Contact:
Eva Lantsoght
E.O.L.Lantsoght@tudelft.nl
elantsoght@usfq.edu.ec
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