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Proof load testing of Reinforced Concrete Slab Bridges in the Netherlands

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The bridges built during the development of the Dutch road network after the Second World War are reaching their originally devised service life. A large subset of the Dutch bridge stock consists of reinforced concrete slab bridges. This bridge type often rates insufficient according to the recently introduced Eurocodes. Therefore, more suitable methods are developed to assess reinforced concrete slab bridges to help transportation officials make informed decisions about the safety and remaining life of the existing bridges.
If information about a bridge is lacking, if the reduction in structural capacity caused by material degradation is unknown, or if an assessment shows insufficient capacity but additional capacity can be expected, a bridge might be suitable for a field test. A proof load test demonstrates that a given bridge can carry a certain load level. In the Netherlands, a number of existing reinforced concrete slab bridges have been proof loaded, and one bridge has been tested to collapse. Bridges with and without material damage were tested. These bridges were heavily instrumented, in order to closely monitor the behavior of the bridge. Critical positions for bending moment and shear were studied.
Based on the proof load tests that were carried out over the past years, a set of recommendations for the systematic preparation, execution, and analysis of proof load test results is compiled. These recommendations will ultimately form the basis of the guideline for proof load testing for the Netherlands, which is currently under development.


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Proof load testing of Reinforced Concrete Slab Bridges in the Netherlands

  1. 1. Challenge the future Delft University of Technology Proof load testing Eva Lantsoght, Cor van der Veen, Ane de Boer, Dick Hordijk of reinforced concrete slab bridges in the Netherlands
  2. 2. 2 Overview • Introduction • Why proof loading? • Existing guidelines? • Past proof load tests by TU Delft • Recommendations • Preparation of proof load tests • Execution of proof load tests • Analysis of proof load tests • Summary and conclusions Slab shear experiments, TU Delft
  3. 3. 3 Why load testing? (1) 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
  4. 4. 4 Why load testing? (2)
  5. 5. 5 Safety philosphy of proof load testing • Safety philosophy • Stop criteria: • Further loading not permitted • Failure near • Irreversible damage near MSc Thesis W. Vos
  6. 6. 6 Proof load testing of bridges • Apply predetermined load to bridge • Information lacking • Damage due to ASR, … • Proof load testing • Immediate approval of bridge • Recalculate updated β • Different goal from diagnostic load testing
  7. 7. 7 Existing Guidelines for proof loading • Europe: DAfStB Richtlinie • Originally derived for buildings • Plain and reinforced concrete • For flexure • Structures with large existing cracking?
  8. 8. 8 Existing Guidelines for proof loading • North America: • Buildings: ACI 437.2M-13 • Bridges: Manual of Bridge Rating Through Load Testing (1998) • ACI 437.2M-13: • Proof load testing load combination • Cyclic loading protocol
  9. 9. 9 Research need • Guideline for proof loading of existing bridges for the Netherlands • Flexure + shear • Measurements? Target proof load?
  10. 10. 10 TU Delft Proof Load Tests • Proof load tests: • Heidijk 2007 • Medemblik 2009 • Vlijmen-Oost 2013 • Halvemaans Bridge 2014 • Ruytenschildt Bridge 2014 • Viaduct Zijlweg 2015 • Viaduct De Beek 2015 Load test to failure of Ruytenschildt Bridge, summer 2014
  11. 11. 11 Heidijk & Medemblik • Heidijk • RC slab bridge • ASR-damage • Hydraulic jacks (handpump) and loading frame • Medemblik • RC girder bridge • Corrosion damage • BELFA
  12. 12. 12 Vlijmen-Oost • Loading: BELFA • Viaduct with ASR • Testing while viaduct was in service • Measurements: • Lasers • Acoustic emissions • LVDTs
  13. 13. 13 Halvemaans Bridge Alkmaar • Load application: Mammoet • Flexural capacity • Bridge closed for 1 night • Measurements: • Lasers • Acoustic emissions • LVDTs
  14. 14. 14 Ruytenschildt Bridge (1) • Load application: Mammoet • Measurements: • Lasers • Acoustic emissions (2 teams) • LVDTs • Sawcut for testing • Testing to failure • 3049 kN in span 1 • 3991 kN in span 2
  15. 15. 15 Ruytenschildt Bridge (2) • Study cracks and deformations for applied loads • Crack formation: acoustic emissions measurements • Control load process
  16. 16. 16 Viaduct Zijlweg • Loading: Mammoet • Viaduct with ASR • Viaduct closed for 1 week • Measurements: • Lasers • Acoustic emissions • LVDTs
  17. 17. 17 Viaduct de Beek • Insufficient flexural capacity • Lane restriction • Limitation: • Test span 1 • Not above highway • Span 2 is critical • Assessment requires plastic redistribution
  18. 18. 18 Preparation steps (1) • Preliminary inspection and rating • Determination of dimensions • Live load: EN 1991-2:2003 • RBK load levels • Different β • Different load factors • In FEM model • mx over 3 m • v over 4d
  19. 19. 19 Preparation steps (2) • Critical position • Bending moment: largest moment • Shear: 2.5d from support • Required proof load • Same shear or bending moment as with load combination • Value → considered safety level
  20. 20. 20 Preparation steps (3) • Sensor plan: • Deflection profiles in longitudinal and transverse direction • Deflection at supports • Strain on bottom of cross- section • Reference strain measurements to correct for T • Opening existing cracks • Opening new cracks • Applied load => load cells
  21. 21. 21 Execution steps (1) • Cyclic loading scheme • Acoustic emission measurements • Check linearity and reproducibility of measurements • Check residual deformations => no non-linearity • Load levels ≈ safety levels CC3 RBK: • Low level to check instrumentation • SLS • Intermediate level • Target proof load
  22. 22. 22 Execution steps (2)
  23. 23. 23 Analysis Steps (1) • Data analysis • Correct for T • Correct for support displacements • Make final plots for report • Finite element model • Updating • cfr. diagnostic load testing
  24. 24. 24 Discussion and future research • Standardize target proof load in Europe • Load model is not representative of vehicles • Load factors for proof loading? • Minimum measurements • “Quick and easy” method for practice • Draft guidelines submitted to RWS in December
  25. 25. 25 Summary and conclusions • Proof loading to approve existing bridges • Existing guidelines: • Only flexure • Cracked structures? • Pilot proof load tests in the Netherlands • Current recommendations • Preparation • Execution • Analysis • First draft guidelines for practice submitted Viaduct Zijlweg
  26. 26. 26 Contact: Eva Lantsoght E.O.L.Lantsoght@tudelft.nl // elantsoght@usfq.edu.ec +31(0)152787449

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