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Challenge the future
DelftUniversity ofTechnology
Shear capacity of slabs under a combination of loads
Eva Lantsoght, Cor van der Veen, Joost Walraven
2Shear capacity of slabs under a combination of loads
Overview
• Introduction
• Recommendations from previous
experiments
• Hypothesis of superposition
• Experiments
• Results
• Superposition
• Support material
• Comparison to proposed method
• ConclusionsS9T6 at failure
3Shear capacity of slabs under a combination of loads
Introduction: Recommendations (1)
• Based on experiments on slabs under a concentrated load
• Evaluating existing solid slab bridges:
• EN 1992-1-1:2005
• 25% reduction of contribution concentrated load close to support
• β =av /2dl
• Combined: βnew =av /2,5dl
• Effective width: French method and minimum 4dl
4Shear capacity of slabs under a combination of loads
Introduction: Recommendations (2)
45 load spreading 45 load spreading – French practice
5Shear capacity of slabs under a combination of loads
Hypothesis of superposition
• Concentrated load over effective width• Distributed loads over full width
• Sum of stresses with combination of loads ≥ stress withconcentrated load only
6Shear capacity of slabs under a combination of loads
Superposition tests(1)
• 2nd series experimental work:
• Slabs under combined loading
• Line load
• Preloading
• 50% of shear strength slab strips
• Concentrated load
• loading until failure
• 26 experiments
• 8 specimens
• Superposition hypothesis valid?
7Shear capacity of slabs under a combination of loads
Superposition tests (2)
8Shear capacity of slabs under a combination of loads
Superposition tests (3)
9Shear capacity of slabs under a combination of loads
Verification of the hypothesis
'
,3
'
,
c combi
c conc
f
f
combination line conc
10Shear capacity of slabs under a combination of loads
Flexible versus rigid supports (1)
support of steel bearings
elastomeric bearings
11Shear capacity of slabs under a combination of loads
Flexible versus rigid supports (2)
• Flexible supports: more ductile failure mode
• Distance a is same, av different
12Shear capacity of slabs under a combination of loads
Flexible versus rigid supports (3)
av as face-to-face distance av as given by code
β = av/2dl with av distance between edge of load and edge of support (or centre of bearing where flexible bearings are used)
13Shear capacity of slabs under a combination of loads
Comparison to proposed method
• EN 1992-1-1:2005• French load spreading method and beff ≥ 4dl
• βnew = av/2,5dl for concentrated load only
0.000
0.500
1.000
1.500
2.000
2.500
3.000
0.00 0.50 1.00 1.50 2.00 2.50 3.00
vR
dc(M
Pa
)
τtest & β (MPa)
14Shear capacity of slabs under a combination of loads
Conclusions
• Recommendations:• effective width
• β =av/2,5dl for concentrated loads
on slabs
• Superposition valid
• Second series confirmsrecommendations
• av = face-to-face distance, also forflexible supports
15Shear capacity of slabs under a combination of loads
Contact:
Eva Lantsoght
+31(0)152787449
