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Seismic Retrofit of the Historic North Torrey Pines Bridge

Seismic Retrofit of the Historic North Torrey Pines Bridge. Jim Gingery, PE, GE Principal Engineer, Kleinfelder, San Diego PhD Student, University of California San Diego. Presentation Outline. The Bridge Site Conditions Earthquake Ground Motion Development

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Seismic Retrofit of the Historic North Torrey Pines Bridge

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  1. Seismic Retrofit of the Historic North Torrey Pines Bridge Jim Gingery, PE, GE Principal Engineer, Kleinfelder, San Diego PhD Student, University of California San Diego

  2. Presentation Outline • The Bridge • Site Conditions • Earthquake Ground Motion Development • Soil-Structure Interaction Evaluations • Retrofit Strategy

  3. The Bridge

  4. The Bridge

  5. North Abutment South Abutment Old River Channel Pre-Construction Circa 1930

  6. Early Days of the Bridge - Late 1930’s

  7. Difficult Field Conditions!

  8. Site Conditions

  9. Earthquake Ground Motions and Soil-Structure Interaction

  10. Earthquake Ground Motion Development • PSHA and DSHA at bedrock • Seed time history selection • Rotation of seeds to principal axes • Spectral matching to FN and FP bedrock targets • Baseline correction • Site response analysis (5 soil profiles)

  11. Directivity Effects on Ground Motions

  12. Directivity of Seed Time Histories

  13. Acceleration Velocity RSPMatch Displacement Seeds matched to target Spectral Matching Process Target (design) Seed time histories

  14. 2 5 1 3 4

  15. Earthquake Ground Motions 5 4 3 2 (2 directions) X (3 EQ’s) X (5 profiles) = 30 site response analyses and time histories! 1

  16. KX Kq KZ Soil-Structure Interaction FZ = KZ*dZ

  17. KX Kq KZ Soil-Structure Interaction 6X6 Foundation Stiffness Matrix

  18. 6X6 Stiffness Matrix for Piled Footings • Individual pile • Pile cap • Pile group • Cross Coupling • Linearization & displacement compatibility

  19. Liquefaction Hazard at the Site • Typical (N1)60 of liquefiable layers 12+/- • Layers typically <=5 ft thick north of Bent 4 • Layers typically 5 to 12 ft thick s. of Bent 4

  20. Liquefaction Hazard at the Site

  21. Seismic Slope Stability

  22. Seismic Slope Stability

  23. Retrofit Strategy

  24. Project Partners City of Del Mar (owner) Simon Wong Enrg. (prime, structural) David Evans & Assc. (nonlinear FE modeling) Caltrans (review) Earth Mechanics, Inc. (peer review) Frieder Seible (peer review)

  25. THANK YOU!

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