Carquinez New Bridge Design

Seismic Evaluation and Independent Check

The replacement of the westbound span of the Carquinez Strait Bridge in Northern California was completed in 2003.  The new suspension bridge has a 728-meter main span, a closed cell orthotropic steel deck, air-spun cables, and concrete towers supported by a foundation system consisting of six 3 meter diameter CISS piles each.  SC Solutions performed an independent check of the seismic performance of this complex bridge structure, examining the following items:

• Utilized a detailed model of an orthotropic deck section in order to verify performance and confirm its stiffness properties,
• Performed dead load and construction sequence analyses,
• Performed a nonlinear time history seismic analysis,
• Captured highly nonlinear geometric effects in the global model,
• Represented material nonlinearities in the global bridge model,
• Detailed foundation models of both towers were created and consisted of plasticity based hysteretic soil springs and moment-curvature beam elements representing CISS piles. 

SC Solutions' gained valuable experience during this project in two key areas:

• The methodology developed to obtain the proper stress and strain distributions in the suspension bridge was extremely important because it greatly affected the global seismic response of the structure.  Proper representation of the foundation systems was  essential to the overall analytical procedure.
• Prior to implementation of these complex foundation systems into the global model, a thorough testing of the stand-alone foundation models, as well as determination of the foundation performance under the lateral loads was conducted and verified.

The replacement project cost was approximately $200 million.