||West Bay Crossing
||The West Bay Crossing
These back-to-back suspension bridges across San Francisco Bay were built in 1936. Today, they carry more than 250,000 vehicles per day.
OPAC evaluated the two-mile-long tandem suspension bridge West Bay Crossing for Caltrans, to determine
seismic vulnerability and retrofitting requirements. The scope of work included the following components:
- Criteria development.
Establishment of load and deformation criteria for determining vulnerability.
- Foundation modeling.
Soil-Structure Interaction modeling of foundations to determine properties and demands.
- Global demand modeling.
Dynamic 3-d modeling to capture global and regional response in an extreme event.
- Local capacity modeling.
Computer and manual evaluation of load and deformation capacities of components.
- Response analysis.
Response spectrum and multi-component time history, linear and nonlinear analyses.
- Vulnerability evaluation.
Estimation of vulnerability based on component capacities, demands, and behavior.
- Retrofit concepts.
Identification of structural concepts for retrofitting the bridge to the new higher standard.
Final design of retrofitting measures is now underway by Caltrans.
Download a Zipped .Avi file [375K] showing the predicted motions in the middle 20 seconds of the Richter-Magnitude 8+ "maximum credible" event.
Visit the Caltrans Bay Bridge Web Site.
Read a technical paper (1,079 KB), by Mark Ketchum & Fletcher Waggoner, presented at the National Seismic Conference on Bridges and Highways, San Diego, California, Dec. 10-13 1995.
This is in Adobe Acrobat (.pdf) portable document format - get the Adobe viewer here if you don't already have it.
Key Staff Experience:
- Kwong M. Cheng served as Principal-in-Charge.
- Mark A. Ketchum served as Project Manager and Lead Investigator with overall project
- Francis Drouillard served as Senior Engineer.
- Fletcher Waggoner served as Project Engineer.
Key Project Issues:
- Linear and nonlinear seismic analysis of a major long-span double-deck bridge structure.
- Development of vulnerability and retrofit criteria for an existing major structure.
- Assessment of structural response considering incoherent seismic wave field and soil-structure interaction
- Coordination of multiple subconsultants.
Client: California Department of Transportation, Sacramento, California.
Date: Study completed in 1994.
Fee: U.S. $500,000
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