Seismic strengthening of an historic arch bridge

This paper describes the seismic evaluation procedure and retrofit design of the historic Russian Gulch Bridge. The work was performed as part of the California Department of Transportation (Caltrans) Phase IZ Seismic Retrofit Program. A displacement-based approach was utilized to assess the critical components of the bridge. Analysis showed that the existing bridge lacked an adequate lateral load carrying system. The retrofit strategy concentrated on measures to create alternative paths for the seismic loads, thereby minimizing the demands on the arch ribs and other elements not designed to resist seismic loads.