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Quick-Release Field Experiments on Seismically Isolated Bridges

Explore comprehensive study on seismic isolated bridges, comparing dynamic behavior before & after retrofit. Measure Winter-Weather Effects. Analyze transverse loading schemes & modeling approaches for performance assessment.

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Quick-Release Field Experiments on Seismically Isolated Bridges

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  1. Quick-Release Field Experiments on Seismically Isolated Bridges Stuart S. Chen, Ph.D., P.E. Associate Professor, University at Buffalo (SUNY), Fulbright Senior Lecturer, ITU

  2. Presentation Outline • Comprehensive Study Overview • Bridges Studied • Loading and Instrumentation Apparatus • Selected Results • Anticipating Seismic Performance • Summary, Conclusions, Recommendations • Acknowledgements

  3. Comprehensive Study!: Overview • Two Similar Bridges, Before and After Seismic Retrofit with Isolation Bearings • Field (System Quick-Release) and Laboratory (Component Reverse-Cyclic) Experiments • Comparing Analytical vs. Experimental Dynamic Behavior • Inferring Seismic Performance from Calibrated Models

  4. Seismic Isolation Concept (Kelly, 2001)

  5. Seismic Isolation Concept (cont’d) (Kelly, 2001)

  6. Bridges’ Plan View

  7. Bridges’ Elevation; Brg. Schedule

  8. Bridge Cross Sections

  9. Bridge Bearing Replacement (Abut.)

  10. Bridge Bearing Replacement (Pier)

  11. Installing Isolation Brgs at Abutments

  12. Southbound Abutment Isolator Kelly, 2001

  13. Southbound Pier Isolator

  14. Northbound Expansion Bearing (non-seismic)

  15. Northbound Bridge Bearings

  16. Objectives • Measure and assess in-situ dynamic behavior and performance of typical slab- on- girder bridge subjected to transverse quick-release loading (steel brgs vs. seismic isolation brgs vs. standard laminated elastomeric brgs) • Quantify in-situ dynamic performance change attributable to bearing retrofits

  17. Objectives, cont’d • Quantify Winter-Weather Effects on In-Situ Performance of Isolation and Elastomeric Bearings • Assess Relative Merits of Several Modeling Approaches (at varying levels of complexity) in predicting transverse transient dynamic behavior of straight skewed slab-on-girder bridge structures

  18. Loading Scheme

  19. Loading Scheme (cont’d)

  20. Loading Scheme (cont’d)

  21. Loading Scheme (cont’d)

  22. Loading Scheme (cont’d)

  23. Loading Scheme (cont’d)

  24. (Under-Bridge) Loading Scheme!

  25. Loading Scheme (cont’d)

  26. Loading Scheme: The Importance of Genuinely Quick Release!

  27. Loading Scheme: Mechanical Fuse

  28. Loading Scheme: Mechanical Fuse in Place

  29. Selected Instrumentation

  30. Selected Instrumentation (cont’d)

  31. Selected Instrumentation (cont’d)

  32. Selected Instrumentation (cont’d)

  33. Selected Instrumentation (cont’d)

  34. Selected Instrumentation (cont’d)

  35. Selected Results: Free Vib’n

  36. Pre-Retrofit in Frequency Domain

  37. 1st 2 Pre-Retrofit Mode Shapes

  38. SAP Model

  39. DRAIN-2DX Model

  40. 3rd Pre-Retrofit Mode Shape

  41. Seismic Isolation Concept: Recall! Sd Sa ξ + T T

  42. Post- Retrofit Time- History at Abutment

  43. Post-Retrofit SB (Linear: “Portion 2”)

  44. Post-Retrofit SB cont’d (Linear: Portion 2)

  45. Post-Retrofit NB (Linear: Portion 2)

  46. Post-Retrofit NB cont’d (Linear: Portion 2)

  47. Selected NB Post-Retrofit T-H’s

  48. Post-Retrofit SB cont’d

  49. Post-Retrofit SB (Nonlinear: Portion 1)

  50. Time, Temperature, Setup Effects (SB)

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