Shear capacity of slabs under a combination of loads
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The document summarizes experiments conducted to evaluate the shear capacity of concrete slabs under a combination of concentrated and distributed loads, finding that the hypothesis of superposition is valid to calculate shear stresses from individual load cases. It recommends an effective width approach using β = av/2.5dl for concentrated loads on slabs and defining the av distance as the face-to-face spacing of supports even for flexible bearings.
Shear capacity of slabs under a combination of loads
- 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