Challenge the future
Delft
University of
Technology
Applying Experimental Results
to the Shear Assessment Method for Solid...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 2
Motivation (1)
Bridges from 60s and...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 3
Motivation (2)
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 4
Motivation (3)
• First checks since...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 5
Live Loads in NEN-EN 1991-2:2003
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 6
Shear Failure
Shear failure of the ...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 7
Slabs under concentrated loads (2)
...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 8
Slabs under concentrated loads (2)
...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 9
Overview of Recommendations
• Evalu...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 10
Experiments (1)
Size: 5m x 2.5m (v...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 11
Experiments (2)
• 2nd series exper...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 12
Experiments (3)
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 13
Slabs vs. Beams
• Transverse load
...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 14
Recommendations: Effective Width (...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 15
Recommendations: Effective Width (...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 16
Recommendations:
Transverse Load R...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 17
Recommendations:
Combining loads
•...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 18
Application to Practice (1)
• Edge...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 19
Application to practice (3)
• Chec...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 20
Application to practice (4)
• Shea...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 21
Summary & Conclusions
• Slabs unde...
Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 22
Contact:
Eva Lantsoght
E.O.L.Lants...
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Applying Experimental Results to the Shear Assessment Method for Solid Slab Bridges

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The combination of increased live loads and a more conservative shear capacity in the recently implemented Eurocodes, resulted in a large number of existing solid slab bridges in the Netherlands being shear-critical upon assessment. However, an enhancement of the shear capacity can occur in slabs under concentrated wheel loads due to transverse load redistribution. To quantify this effect, a comprehensive series of experiments on slabs and slabs strips under a concentrated load near to the support and under a combination of a concentrated and a line load was carried out. The experiments show the difference in behaviour for slabs, carrying the load in a two-dimensional way, as compared to beams in shear. The results from the laboratory research are used to develop recommendations, that are easily used in combination with the codes. These recommendations are implemented in a spreadsheet-based first-level assessment tool, the Quick Scan method. The assessment with this tool of selected cases of existing solid slab bridges shows that applying the experimental results into the assessment practice leads to an improved selection ability of the Quick Scan method.

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Applying Experimental Results to the Shear Assessment Method for Solid Slab Bridges

  1. 1. Challenge the future Delft University of Technology Applying Experimental Results to the Shear Assessment Method for Solid Slab Bridges Eva Lantsoght, Cor van der Veen, Joost Walraven, Ane de Boer
  2. 2. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 2 Motivation (1) Bridges from 60s and 70s The Hague in 1959 Increased live loads heavy and long truck (600 kN > perm. max = 50 ton) End of service life + larger loads
  3. 3. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 3 Motivation (2)
  4. 4. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 4 Motivation (3) • First checks since mid-2000s • 3715 structures to be studied • 600 slab bridges shear-critical • But: checks according to design rules • => Residual capacity & remaining lifetime??? • Hidden reserves of the bearing capacity • Eg. Transverse load redistribution Highways in the Netherlands
  5. 5. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 5 Live Loads in NEN-EN 1991-2:2003
  6. 6. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 6 Shear Failure Shear failure of the de la Concorde bridge, Laval, Canada Shear failures of bridges: rare but brittle failures
  7. 7. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 7 Slabs under concentrated loads (2) • Shear stress over effective width • Fixed width, eg. 1 m • Load spreading method
  8. 8. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 8 Slabs under concentrated loads (2) • Shear stress over effective width • Fixed width, eg. 1 m • Load spreading method
  9. 9. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 9 Overview of Recommendations • Evaluating existing solid slab bridges: • NEN-EN 1992-1-1:2005 • 25% reduction of contribution concentrated load close to support • β =av/2d • Combined: βnew =av/2.5d • Effective width: French method and minimum 4d
  10. 10. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 10 Experiments (1) Size: 5m x 2.5m (variable) x 0.3m = scale 1:2 Continuous support, Line supports First series: concentrated load: vary a/d and position along width
  11. 11. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 11 Experiments (2) • 2nd series experimental work: • Slabs under combined loading • Line load • Preloading • 50% of strength from slab strips • Concentrated load until failure • Conclusions from 1st series valid when combining loads? • 26 experiments, 8 slabs • Total: 156 experiments, 38 slabs
  12. 12. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 12 Experiments (3)
  13. 13. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 13 Slabs vs. Beams • Transverse load redistribution • Geometry governing in slabs • Location of load • result of different load- carrying paths • Mid support vs end support • influence of transverse moment • Wheel size • more 3D action
  14. 14. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 14 Recommendations: Effective Width (1) 5000 1000 2500 b (mm) 20001500 0.5m 2.5m
  15. 15. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 15 Recommendations: Effective Width (2) • Statistical analysis of Vexp/VEC with beff1 and beff2 • NLFEA: shear stress distribution at the support • Lower bound: 4dl
  16. 16. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 16 Recommendations: Transverse Load Redistribution • Comparison between experiments and EN 1992-1- 1:2005 • based on normal distribution • characteristic value at least 1.25 • Combination with β = av /2dl and enhancement factor 1.25 βnew = av /2.5dl for 0.5dl ≤ av ≤ 2.5dl
  17. 17. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 17 Recommendations: Combining loads • Experiments on slabs under line load + concentrated load • Superposition is safe assumption • Concentrated loads over effective width • Distributed loads over full width
  18. 18. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 18 Application to Practice (1) • Edge + 3 lanes • First lane: av = 2.5dl • Second and third lane: effective width
  19. 19. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 19 Application to practice (3) • Checks at indicated sections • 9 existing Dutch solid slab bridges
  20. 20. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 20 Application to practice (4) • Shear stresses: influence of recommendations • QS-EC2: wheel loads at av = 2.5dl • QS-DutchCode: wheel loads at av = dl • QS-EC2 18% reduction in loads • Shear capacity: • QS-EC2: vRd,c ~ ρ, d • low reinforcement + deep section = small shear capacity • QS-DutchCode: τ1 ~ fck only • QS-EC2 improved selection ability
  21. 21. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 21 Summary & Conclusions • Slabs under concentrated loads behave differently in shear than beams • Beneficial effect of transverse load redistribution • Recommendations: • effective width from French method • minimum 4dl • reduction factor βnew = av /2.5dl • superposition valid
  22. 22. Applying Experimental Results to the Shear Asssessment Method for Solid Slab Bridges 22 Contact: Eva Lantsoght E.O.L.Lantsoght@tudelft.nl +31(0)152787449

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