Load testing of reinforced concrete bridges in the Netherlands

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As the bridge stock in The Netherlands and Europe is ageing, various methods to analyze existing bridges are being studied. Load testing of bridges is an option to study the capacity when crucial information about the structure is lacking. This information could be related to the material (for example, the effect of ASR on the capacity) as well as to the structural system (for example, the effect of restraints at the supports or transverse redistribution capacity).
When it is decided to load test a bridge, the question arises which maximum load should be attained during the experiment to approve the capacity of the bridge, and which criteria, based on the measurements during the test, would indicate that the test needs to be aborted before reaching the maximum desired load (the “stop criteria”).
A number of reinforced concrete slab bridges have been load tested over the course of the past few years. These load tests were pilot cases, in which the bridges were heavily equipped with sensors, to study the bridges’ behavior at critical positions for bending moment and shear. The test results were then extensively analyzed, and compared to the stop criteria available in the currently used codes and guidelines.
As a result of the analysis and experiments, recommendations are given for proof loading of bridges. These recommendations are important, since they will form the basis of a guideline for proof loading of existing concrete bridges that is under development in The Netherlands.

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Load testing of reinforced concrete bridges in the Netherlands

  1. 1.   Dr. ir. Eva Lantsoght 10/28/2016 1
  2. 2.  General overview of work/research since graduating from VUB  Current research line: (proof) load testing 10/28/2016 2
  3. 3.  2003-2008: burgerlijk ingenieur bouwkunde  2008-2009: M.S. in structural engineering, Georgia Institute of Technology 10/28/2016 3
  4. 4.  2009-2013: PhD in Civil Engineering  Concrete Structures research group  Promotor: Joost Walraven  Co-Promotor: Cor van der Veen 10/28/2016 4
  5. 5.  Experiments o Shear in reinforced concrete slabs o 156 experiments  Analytical work o Extended Strip Model – plastic analysis method for shear in slabs o Probability-based improvement for EC shear formula based on experiments  Practical application o Quick Scan for Rijkswaterstaat 10/28/2016 5
  6. 6.  2013 – …  B.Sc. level, 5-year program  Teaching (3 courses/semester): o Reinforced Concrete I o Reinforced Concrete II o Construction Materials Lab o Design of Pavements o Structural Analysis I  Research with students for “Trabajo de Titulacion” 10/28/2016 6
  7. 7.  2013-2016: Profesor auxiliar  2016 (?) - … : Profesor Investigador Principal Titular after concurso de merecimientos y oposiciones => reduction of teaching, more research  ACI student chapter  ASCE student chapter  2013 – 2016: Starting ICV-Lab 10/28/2016 7
  8. 8.  Research: o Publications of PhD research o Analysis existing bridge Tambura o Torsion in slabs o Digital Image Correlation with cheap tools o Chancellor Grant 2015: Extended Strip Model o Chancellor Grant 2016: Stop criteria load testing (research line TU Delft) 10/28/2016 8
  9. 9.  Research lines: o Difficulties: • contact with Ministry of Public Works? • Infomation (structural plans?) • Mentality: no interest in existing structures • Limited facilities • No research group o Approach: • Desk research • Presentations about existing structures and maintenance • Cooperation through international committees 10/28/2016 9
  10. 10.  2013 – now: 0,2 fte  Short projects  Summer 2013: o Quick Scan spreadsheets for Rijkswaterstaat  Summer 2014: o Fatigue of high-strenght concrete: proposal for Dutch code o Ruytenschildt Bridge collapse test 10/28/2016 10
  11. 11.  Summer 2015: o Effect of ASR on shear- and bending moment capacity o Proof load test viaduct Zijlweg o Support for research line proof load testing 10/28/2016 11
  12. 12.  Summer 2016 o Research line proof load testing o Beam tests + analysis of results o Analysis results of proof load test viaduct De Beek o Literature review o Overview previous proof load tests in NL o First draft guideline o Vechtbrug: last week – collapse test 10/28/2016 12
  13. 13.  ACI-ASCE 421: Design of reinforced concrete slabs  ACI-ASCE 445: Shear & Torsion  ACI-DAfStB 445-D: Shear Databases  ACI 342: Evaluation of Concrete Bridges and Bridge Elements  TRB AFF30: Concrete Bridges  TRB AFF40: Testing and Evaluation of Transportation Structures  IABMAS, IALCCE, IABSE, fib 10/28/2016 13
  14. 14.  Advanced structural engineering  2 junior engineers  Bridges: La Armenia, Los Pajaros (ILM), Villorita  Buildings  Project on concrete masonry houses (EQ-resistant) for coast of Ecuador 10/28/2016 14
  15. 15.  Introduction o Why proof loading? o Stop criteria?  Overview of existing guidelines  Past proof load tests by TU Delft  Recommendations o Preparation of proof load tests o Execution of proof load tests  Summary and conclusions Slab shear experiments, TU Delft 10/28/2016 15
  16. 16. 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 10/28/2016 16
  17. 17. 10/28/2016 17
  18. 18. Diagnostic load testing Proof load testing 10/28/2016 18 Barcza ridge, Poland (Olaszek et al., 2012) Delaware (Jones, 2011)
  19. 19. Diagnostic load testing  Calibration of FEM  Strain gages over girder height  Low load levels  Rating with updated FEM Proof load testing  Directly demonstrate that bridge fulfils criteria  Higher load levels  Larger involved risk  Follow measurements  Stop criteria 10/28/2016 19
  20. 20.  Safety philosophy  Stop criteria: o Further loading not permitted o Failure near o Irreversible damage near MSc Thesis W. Vos 10/28/2016 20
  21. 21.  Apply predetermined load to bridge o Information lacking o Damage due to ASR, …  Proof load testing o Immediate approval of bridge o Recalculate updated β o RC slab bridges 10/28/2016 21
  22. 22.  Europe: DAfStB Richtlinie  Stop criteria o Concrete strain o Steel strain o Crack width and residual crack width (new & existing cracks) o Residual deflection  For flexure  Structures with large existing cracking? 10/28/2016 22
  23. 23.  North America: o Buildings: ACI 437.2M-13 o Bridges: Manual of Bridge Rating Through Load Testing (1998)  ACI 437.2M-13 stop criteria: o Residual deflection o Permanency ratio o Deviation from Linearity Index 10/28/2016 23
  24. 24.  Guideline for proof loading of existing bridges for the Netherlands  Flexure + shear  Stop criteria? 10/28/2016 24
  25. 25.  Proof load tests: o Heidijk 2007 o Medemblik 2009 o Vlijmen-Oost 2013 o Halvemaans Bridge 2014 o Ruytenschildt Bridge 2014 o Viaduct in the Zijlweg 2015 o Viaduct De Beek 2015 o Vecht Bridge 2016 Load test to failure of Ruytenschildt Bridge, summer 2014 10/28/2016 25
  26. 26.  Heidijk o RC slab bridge o ASR-induced damage o Loading frame o RWS + TNO  Medemblik o Girder bridge o BELFA o RWS + TNO + ifem 10/28/2016 26
  27. 27.  Video 10/28/2016 27
  28. 28.  BELFA  Viaduct with ASR-damage  Viaduct remained open to traffic  Disturbs AE measurements  TU Delft + ifem: measurements  Bridge approved 10/28/2016 28
  29. 29.  System with load spreader beam  Bending moment capacity  1 night closure of bridge  TU Delft: measurements  Bridge from 1930s  Approved with proof load test 10/28/2016 29
  30. 30.  Existing reinforced concrete slab bridge (1962)  Test to failure in two spans  4 concentrated load – one tandem  Cyclic loading protocol  Failure only achieved in span 2 10/28/2016 30
  31. 31. Existing bridge Partial demolition and building new bridge 10/28/2016 31
  32. 32. 10/28/2016 32
  33. 33.  Proof load test for bending moment and shear  Bridge closed for 1 week  Viaduct over highway  ASR-induced damage  Approved thanks to proof load test 10/28/2016 33
  34. 34.  No material damage  Extensive cracking  Proof load test on Span 1  Span 2 over highway  Shear and flexure position  Bridge approved if 7% plastic redistribution in Span 2 is OK  Check for durability/corrosion 10/28/2016 34
  35. 35.  Video 10/28/2016 35
  36. 36.  Determination of dimensions  Live load: EN 1991-2:2003  RBK load levels o Different β o Different load factors  In FEM model o mx over 3 m o v over 4d 10/28/2016 36
  37. 37.  Critical position o Bending moment: largest moment o Shear: 2.5d from Support  Required proof load o Same shear or bending moment as with load combination o Value → considered safety level 10/28/2016 37
  38. 38.  Cyclic loading scheme o Acoustic emission measurements o Check linearity and reproducibility of measurements o Check residual deformations  Stop criteria o Evaluated during tests o Research in progress o Criteria for shear failure need to be developed 10/28/2016 38
  39. 39.  Beams from Ruytenschildt Bridge o Cyclic loading protocol o Tests: Failure in shear and flexure o Measurements: • Lasers: deflection of beam • LVDTs: crack opening • Acoustic emission sensors Beams RSB01 after failure (Yang, 2015) Yang, Y. (2015). "Experimental Studies on the Structural Behaviours of Beams from Ruytenschildt Bridge," Stevin Report 25.5-15-09, Delft University of Technology, Delft, 76 pp. Beams RSB02B after failure (Yang, 2015) 10/28/2016 39
  40. 40. RSB 01F 02A 02B 03F 03A d (mm) 503 515.5 520 521 515 Ac (m2) 0.290 0.297 0.307 0.596 0.537 Rebar 4Ø22 4Ø19 4Ø22 4Ø19 4Ø22 5Ø19 9Ø22 8Ø19 7Ø22 8Ø19 ρl 0.91% 0.89% 0.96% 0.95% 0.92% 10/28/2016 40
  41. 41.  Analysis of stop criteria ACI 437.2M-13 and DAfStB Richtlinie for RSB03F – Flexure test ACI 437.2M-13 Criterion Load (kN) DAfStB Criterion Load (kN) Δr 340 Δr 150 Ipr >Pu w new crack 300 IDL 250 Strain - PACI,st 250 PDA,st 150 Pu 606.6 Pu 606.6 PACI,st/Pu 0.41 PDA,st/Pu 0.25 Tersteeg, R. H. D. (2015). "Proefbelastingen op betonnen bruggen," B.Sc. Thesis, Delft University of Technology, Delft, The Netherlands, pp. 69. 10/28/2016 41
  42. 42.  Analysis of stop criteria ACI 437.2M-13 and DAfStB Richtlinie for RSB03A – Shear test ACI 437.2M-13 Criterion Load (kN) DAfStB Criterion Load (kN) Δr >Pu Δr >Pu Ipr >Pu w new crack 690 IDL 390 Strain - PACI,st 390 PDA,st 690 Pu 706.7 Pu 706.7 PACI,st/Pu 0.55 PDA,st/Pu 0.98 Tersteeg, R. H. D. (2015). "Proefbelastingen op betonnen bruggen," B.Sc. Thesis, Delft University of Technology, Delft, The Netherlands, pp. 69. 10/28/2016 42
  43. 43.  Use cyclic load protocol o Study linearity and repeatability of results  Flexure: Stop criteria exceeded long before failure o Suitable stop criteria • Crack width criterion from DAfStB + add lower bound • Residual deflection DAfStB / ACI 437.2M-13 + minimum load level • Deviation from Linearity ACI 437.2M-13: consistent performance except for retested beam • BUT: Deviation from Linearity and Permanency Ratio depend on applied loading protocol  Shear: o Need to develop stop criteria o Research on acoustic emission measurements 10/28/2016 43
  44. 44.  Controlled experiments in laboratory  Heavily instrumented beams  Beams: part of series of shear tests  Study of stop criteria and loading protocol o Interrelated!  First proposal for stop criteria for guideline 10/28/2016 44
  45. 45. Previously cracked in bending moment or not? Failure mechanism Uncracked Cracked Flexural failure Concrete strains wmax ≤ 0.5 mm wres ≤ 0.1 mm Stiffness reduction ≤ 25 % Deformation profiles Load-displacement graph Concrete strains wmax ≤ 0.5 mm wres ≤ 0.1 mm Stiffness reduction ≤ 5 % Deformation profiles Load-displacement graph Shear failure Concrete strains wmax ≤ 0.3 mm Stiffness reduction ≤ 5 % Deformation profiles Load-displacement graph Concrete strains Stiffness reduction ≤ 5 % Deformation profiles Load-displacement graph 10/28/2016 45
  46. 46. 10/28/2016 46
  47. 47.  Proof loading to approve existing bridges  Existing guidelines: o Only flexure o Cracked structures?  Research on stop criteria  Determination of maximum proof load o LFEA o Different safety levels  Execution o Cyclic loading protocol o Safely applying large loads Viaduct Zijlweg, tested in summer 2015 10/28/2016 47
  48. 48. Contact: Eva Lantsoght elantsoght@usfq.edu.ec // E.O.L.Lantsoght@tudelft.nl 10/28/2016 48

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