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Prolonging the service life of existing reinforced concrete slab bridges

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Prolonging the service life of existing reinforced concrete slab bridges

  1. 1. 28-05-2013 Challenge the future Delft University of Technology Prolonging the service life of existing reinforced concrete slab bridges through experimental studies on the shear capacity Eva Lantsoght, Cor van der Veen, Joost Walraven
  2. 2. 2Prolonging the service life of existing reinforced concrete slab bridges Introduction 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
  3. 3. 3Prolonging the service life of existing reinforced concrete slab bridges Introduction Assessment strategy Required safety level: Repair level: 3.3 ≤ β ≤ 3.6 => Research on additional load-bearing mechanisms in slab bridges
  4. 4. 4Prolonging the service life of existing reinforced concrete slab bridges Introduction Transverse load redistribution • Additional dimension in slabs • Transverse redistribution capacity • Direct load transfer to support
  5. 5. 5Prolonging the service life of existing reinforced concrete slab bridges Experiments Size: 5m x 2.5m (variable) x 0.3m = scale 1:2 Continuous support, Line supports Concentrated load: vary a/d and position along width
  6. 6. 6Prolonging the service life of existing reinforced concrete slab bridges Code extension proposal Limit State function Experiment vs. Design value • Experiment • mean values • Test/Predicted ratio • Design value • characteristic values f d P P R R Reliability analysis based on load and resistance
  7. 7. 7Prolonging the service life of existing reinforced concrete slab bridges Code extension proposal Random variables 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 2 4 6 8 10 12 36 38 40 42 44 46 48 50 52 More Frequency fc,cube,mean (MPa) Frequency Cumulative % concrete compressive strengthTest/Predicted
  8. 8. 8Prolonging the service life of existing reinforced concrete slab bridges Code extension proposal Slabs subjected to Wheel Loads • Enhancement factor depends on fck • Experiments: fck not as in shear formula • Effect of reduced support width • Proposal for av ≤ 2.5dl 1/3 , , , ,100 1.9 225 ck Rd c prop Rd c l ck eff red l f V C k f b d , 0.52 0.48 sup eff red eff l b b b
  9. 9. 9Prolonging the service life of existing reinforced concrete slab bridges Economics • Repair cost • Demolition cost • Recycling cost • New construction Environment • Impact of repair • Impact of replacement • CO2 emissions • Materials • Transport Social • Visual impact • Traffic delays • Employment Sustainability
  10. 10. 10Prolonging the service life of existing reinforced concrete slab bridges Impact on Sustainability Example replacement of 3-span slab bridge (deck only) • Economic cost: 500k – 640k € • Environmental cost: 136 ton CO2 • Blast furnace cement: 74 ton CO2 • Portland slag cement: 122 ton CO2 • Social cost: case-dependent • can be 9 times economic cost • Scope: 600 slab bridges
  11. 11. 11Prolonging the service life of existing reinforced concrete slab bridges Summary & Conclusions 1. Safety level “Repair” 2. Prolonging service life = savings at end-of-life stage 3. Utilize transverse load redistribution capacity of slabs 4. Code extension proposal 5. Impact is economic, environmental and social
  12. 12. 12Prolonging the service life of existing reinforced concrete slab bridges Contact: Eva Lantsoght E.O.L.Lantsoght@tudelft.nl +31(0)152787449

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