Benicia-Martinez Bridge Seismic Retrofit

Seismic Evaluation and Independent Check

Constructed in 1962, the Benicia-Martinez Bridge carried Route 680 traffic over the Carquinez Strait between the cities of Benicia in Solano County and Martinez in Contra Costa County.  Over 90,000 vehicles crossed the bridge each day. The bridge was constructed to an initial 4-lane width of 67 feet. In 1991, the bridge was widened to its present width of 77 feet to accommodate six lanes of traffic.

The  retrofit strategy included replacing the existing steel bearings with isolation bearings, adding a new tapered exterior concrete jacket to most of the piers and adding additional caissons with tie down anchors. Other work included strengthening the approach columns and widening the column footings, placing larger expansion joints at the abutments and strengthening the steel members which comprise the truss structure.

SC Solutions portion of the work consisted of:

• Performing an independent check of the as-built and several retrofit strategy alternative structures,
• Conducted Nonlinear multi-support time history analyses  to evaluate structural response to the Maximum Credible Earthquake,
• Performed local finite-element model studies to assess behavior of various retrofitted structural components for use in the design phase,
• Evaluated the proposed friction pendulum bearings through the development of three separate models.