Application of Modified Bond Model to the capacity of Ruytenschildt Bridge
Application of Modified Bond Model to the capacity of Ruytenschildt Bridge
The Ruytenschildt bridge in Friesland is a continuously supported concrete slab bridge, and was tested in two spans to failure in August 2014. The results of this experiment are valuable for the analysis of existing slab bridges and for analyzing the moment and shear capacity of reinforced concrete slabs and slab bridges. Earlier analyses found that a large number of existing slab bridges in The Netherlands rate as insufficient for shear. However, these analyses did not take into account the beneficial effect of transverse load redistribution. Therefore, the Modified Bond Model was developed. This model covers beam shear, punching shear and flexure for reinforced concrete slabs. The test results are now to compare to the predictions with the Modified Bond Model. Since the Modified Bond Model is independent of the failure mode, the maximum load that is found can be directly correlated to the maximum tandem load in the experiment. Comparing the test results on the bridge with the predictions based on the Modified Bond Model shows good correspondence. The results are also compared to a new proposal for vmin, the minimum shear stress at which shear failure takes place. For smaller value, a moment failure takes place. While the presented results only show a comparison between 2 tests on an existing bridge and the proposed Modified Bond Model, the results indicate that the Modified Bond Model can become a useful tool for design and analysis of reinforced concrete slabs based on the principles of the theory of plasticity.
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Application of Modified Bond Model to the capacity of Ruytenschildt Bridge
- 1. Challenge the future Delft University of Technology Application of Modified Bond Model to capacity of Ruytenschildt Bridge Eva Lantsoght, Cor van der Veen, Ane de Boer, Dick Hordijk
- 2. 2 Overview • Introduction to case • Modified Bond Model • Test results • Comparison results and MBM • Summary & Conclusions Slab shear experiments, TU Delft
- 3. 3 Proofloading Case Ruytenschildt Bridge • Proofloading to assess capacity of existing bridge • ASR affected bridges • Insufficient information • Study cracks and deformations for applied loads • Crack formation: acoustic emissions measurements • Control load process • Ruytenschildt Bridge: testing to failure
- 4. 4 Proofloading Ruytenschildt Bridge Existing bridge Partial demolition and building new bridge
- 6. 6 Bond Model (1) • Alexander and Simmonds, 1990 • For slabs with concentrated load in middle
- 8. 8 Modified Bond Model (1) • Adapted for slabs with concentrated load close to support • Geometry is governing as in experiments • Determine factor that reduces capacity of “radial” strip • Maximum load: based on sum capacity of 4 strips
- 9. 9 Unequal loading of strips • Static equilibrium • v2,x reaches max before v1,x ' 1, 0.1667x c a v f d L a
- 10. 10 Loads close to free edge Edge effect: when length of strip is too small to develop loaded length lw
- 11. 11 Cross-sections Ruytenschildt Bridge • Testing in span 1 and span 2 • close to end support • close to mid support • Critical position for shear
- 12. 12 Test results proofloading Span 1 • Maximum load 3049 kN • Maximum available load for span 1 • Flexural cracks • No failure • Order additional load for test 2! • Prediction MBM: 2864 kN • Tested/Predicted = 1.06 • Tested; not failure load 0 500 1000 1500 2000 2500 3000 3500 0 5000 10000 15000 20000 25000 Load(kN) time (s)
- 13. 13 Test results proofloading Span 2 • Maximum load 3991 kN • Large flexural cracks • Flexural failure • yielding of reinforcement • Settlement of bridge pier with 1.5cm • Elastic recovery to 8mm • Prediction MBM: 3816 kN • Tested/Predicted = 1.05 • Bent-up bars?? 0 500 1000 1500 2000 2500 3000 3500 4000 4500 0 2000 4000 6000 8000 10000 Load(kN) Time(s)
- 14. 14 Conclusions • Ruytenschildt Bridge • Testing to failure in 2 spans • Measurements • Modified Bond Model • Plasticity-based model • For analysis of capacity of slabs • MBM shows good predictions of capacity of bridge • For limited number of field experiments
- 15. 15 Contact: Eva Lantsoght E.O.L.Lantsoght@tudelft.nl // elantsoght@usfq.edu.ec +31(0)152787449