Recommendations for the Shear Assessment of Reinforced Concrete Solid Slab Bridges
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Recommendations for the Shear Assessment of Reinforced Concrete Solid Slab Bridges

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As a result of the heavier live load models and more conservative shear approaches prescribed by the recently implemented Eurocodes, a large number of existing reinforced concrete solid slab bridges ...

As a result of the heavier live load models and more conservative shear approaches prescribed by the recently implemented Eurocodes, a large number of existing reinforced concrete solid slab bridges in the Netherlands were found to be shear-critical. The beneficial effect of the transverse load redistribution in slabs under concentrated loads is not taken into account. To quantify this effect, a comprehensive number of experiments was carried out. These results are used to formulate recommendations for the assessment practice for the case of solid slab bridges. The recommendations focus on the effective width over which the axle load can be distributed and its lower bound, the beneficial effect of transverse load redistribution and the influence of the yield strength of the reinforcement on the lower bound of the shear capacity. These recommendations are implemented in the “Quick Scan” method, leading to a significant reduction of the shear stresses.

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Recommendations for the Shear Assessment of Reinforced Concrete Solid Slab Bridges Recommendations for the Shear Assessment of Reinforced Concrete Solid Slab Bridges Presentation Transcript

  • Recommendations for the Shear 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
  • Problem statement Bridges from 60s and 70s The Hague in 1959 Increased live loads common heavy and long truck (600 kN) End of service life + larger loads
  • Highway network in the Netherlands • NL: 60% of bridges built before 1976 • Assessment: shear critical in 600 slab bridges • Residual capacity? Highways in the Netherlands
  • Assessment practice • Development of 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
  • Explanation of recommendations (1) Choice of effective width 5000 1000 1500 2000 2500 b (mm)
  • 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%
  • 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
  • Explanation of recommendations (4) Hypothesis of Superposition
  • Explanation of recommendations (5) Hypothesis of Superposition combination line conc    ' , 3 ' , c combi c conc f f
  • 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
  • Results Most unfavorable position Detail of load spreading
  • Results Unity checks (1) • Checks required at indicated sections • 9 existing Dutch solid slab bridges + MBE example
  • 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
  • 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
  • Contact: Eva Lantsoght E.O.L.Lantsoght@tudelft.nl / elantsoght@usfq.edu.ec