Seismic Retrofit Program for Los Angeles Bridges

This paper details the work of the recent Bridge Seismic Retrofit Program for the city of Los Angeles. We describe the scope of the work completed and project funding through local and federal sources. The criteria used for the categorization of a bridge as a historical structure is explained, and the subsequent funding and design impacts are detailed. Methods of prioritizing the bridge retrofits using a weighted formula based on replacement cost, condition of the bridge, bridge traffic, and age of the structure are introduced. The engineering solutions to the typical bridge seismic deficiencies of loss of support at the rocker bearings and expansion hinges, column failures, failures of pier walls, foundation failures, and abutment failures are all reviewed. We summarize the bridge construction program history and progress. The work done to one bridge, the Cesar Chavez Bridge, is detailed to illustrate a representative project within the program. Our conclusions identify the successes and shortcomings of this major infrastructure improvement program.