presentation given at the 2013 fib symposium

1. Challenge the future
Delft
University of
Technology
Shear capacity of slabs
under a combination of loads
Eva Lantsoght, Cor van der Veen, Joost Walraven

2. 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
• Conclusions
S9T6 at failure

3. 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

4. 4Shear capacity of slabs under a combination of loads
Introduction: Recommendations (2)
45 load spreading 45 load spreading – French practice

5. 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 with
concentrated load only

6. 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?

7. 7Shear capacity of slabs under a combination of loads
Superposition tests (2)

8. 8Shear capacity of slabs under a combination of loads
Superposition tests (3)

9. 9Shear capacity of slabs under a combination of loads
Verification of the hypothesis
'
,
3
'
,
c combi
c conc
f
f
combination line conc   

10. 10Shear capacity of slabs under a combination of loads
Flexible versus rigid supports (1)
support of steel bearings
elastomeric bearings

11. 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

12. 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)

13. 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
vRdc(MPa)
τtest & β (MPa)

14. 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 confirms
recommendations
• av = face-to-face distance, also for
flexible supports

15. 15Shear capacity of slabs under a combination of loads
Contact:
Eva Lantsoght
E.O.L.Lantsoght@tudelft.nl
+31(0)152787449