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Recommendations for the Shear Assessment of Reinforced Concrete Solid Slab Bridges
The document provides recommendations for the shear assessment of reinforced concrete solid slab bridges, specifically addressing maintenance of these structures built in the 60s and 70s in the Netherlands. Key recommendations include using an effective width based on a French method, applying a minimum width of 4d, and a new reduction factor for load assessments. The findings indicate that adjustments based on these recommendations could lead to significant improvements in evaluating shear capacity in existing bridges.
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Recommendations for the Shear Assessment of Reinforced Concrete Solid Slab Bridges
- 1. Recommendations for theShear Assessment of Reinforced Concrete Solid Slab Bridges Eva Lantsoght – Universidad San Francisco de Quito & Delft University of Technology Cor van der Veen - Delft University of Technology Ane de Boer – Rijkswaterstaat Joost Walraven – Delft University of Technology
- 2. Problem statement Bridges from60s and 70s The Hague in 1959 Increased live loads common heavy and long truck (600 kN) End of service life + larger loads
- 3. Highway network inthe Netherlands • NL: 60% of bridges built before 1976 • Assessment: shear critical in 600 slab bridges • Residual capacity? Highways in the Netherlands
- 4. Assessment practice • Developmentof NEN 8700 series for existing structures Load Levels: New, Repair, Unfit for Use – Repair level: β < 3.8 (3.6 for bridges built before 2012) – EC • Level of Approximation approach in Model Code – LoA I: Quick Scan => unity check
- 5. Explanation of recommendations(1) Choice of effective width 5000 1000 1500 2000 2500 b (mm)
- 6. Explanation of recommendations(2) Choice of effective width • Calculated from series vs. 45° load spreading • minimum 4d • 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%
- 7. Explanation of recommendations(3) 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
- 8. Explanation of recommendations(4) Hypothesis of Superposition
- 9. Explanation of recommendations(5) Hypothesis of Superposition combination line conc ' , 3 ' , c combi c conc f f
- 10. Application to practice •Evaluating existing solid slab bridges: – 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
- 11. Results Most unfavorable position Detailof load spreading
- 12. Results Unity checks (1) •Checks required at indicated sections • 9 existing Dutch solid slab bridges + MBE example
- 13. Results Unity checks (2) •Shear stresses: influence of recommendations – QS-EC2: wheel loads at av = 2.5dl – QS-Dutch Code: 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
- 14. Summary & Conclusion •Recommendations: – effective width from French method – minimum 4d – reduction factor βnew = av /2.5dl – superposition valid • Quick Scan: tool for first round of assessments
- 15. Contact: Eva Lantsoght E.O.L.Lantsoght@tudelft.nl /elantsoght@usfq.edu.ec