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

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 2 Presentation Outline The Bridge Site Conditions Earthquake Ground Motion Development Soil-Structure Interaction Evaluations Retrofit Strategy

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 3 The Bridge

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 4 The Bridge

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 5 South Abutment North AbutmentOld River Channel Pre-Construction Circa 1930

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 6 Early Days of the Bridge - Late 1930’s

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 7 Difficult Field Conditions!

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 8 Site Conditions

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 9 Earthquake Ground Motions and Soil-Structure Interaction

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 10 Earthquake Ground Motion Development 1. PSHA and DSHA at bedrock 2. Seed time history selection 3. Rotation of seeds to principal axes 4. Spectral matching to FN and FP bedrock targets 5. Baseline correction 6. Site response analysis (5 soil profiles)

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 11 Directivity Effects on Ground Motions

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 12 Directivity of Seed Time Histories

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 13 Spectral Matching Process Acceleration Displacement Velocity Seed time histories Target (design) Seeds matched to target RSPMatch

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 14

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 16 Earthquake Ground Motions (2 directions) X (3 EQ’s) X (5 profiles) = 30 site response analyses and time histories!

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 17 Soil-Structure Interaction KK KZKZ KXKX F Z = K Z *  Z

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 18 Soil-Structure Interaction KK KZKZ KXKX 6X6 Foundation Stiffness Matrix

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 19 6X6 Stiffness Matrix for Piled Footings Individual pile Pile cap Pile group Cross Coupling Linearization & displacement compatibility

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 20 Liquefaction Hazard at the Site Typical (N 1 ) 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

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 21 Liquefaction Hazard at the Site

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 22 Seismic Slope Stability

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 23 Seismic Slope Stability

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 24 Retrofit Strategy

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 25 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)

KLEINFELDER CONFIDENTIAL North Torrey Pines Bridge Seismic Retrofit 26 THANK YOU!