Monterey County, California Bridges: Bradley Road Bridge across the Salinas River

July 2016 (35.8641, -120.8097) Bradley Road Bridge

Similar to last week's Cattlemen Road Bridge, the Bradley Road Bridge is a deck truss with concrete T beam approaches. Both bridges are about 1700 ft long but the Bradley Road Bridge has better access along its flanks.

However, unlike the Cattlemen Road Bridge there was no seismic retrofit on the Bradley Road Bridge. The approach spans are supported on pier walls that turn into columns at the top. This is to allow flooding to flow around the piers unimpeded by columns. Not a great seismic design, although the infill walls between the two center columns provides some shear strength transversely (see photo above).

The main spans are 140 ft long Warren trusses on skewed pier walls. This county-owned bridge was built in 1930 and rehabilitated in 1954. The deck is only 24 ft wide and includes a small diameter horizontal curve.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

California's Bridges: Benicia-Martinez Bridges across the Carquinez Straits (3)

1999 (38.043 deg, -122.122 deg.) Benicia-Martinez Bridges

The southbound Benicia Martinez Bridge is composed of seven 528 ft long truss spans. The seismic retrofit would have required extensive work to strengthen the piers and foundations for the resulting large inertia force. The use of 10 ft diameter friction pendulum bearings reduced the earthquake forces being carried by the piers which reduced the cost of the retrofit. 

Each bearing was tested on the giant shake table at UC San Diego before it was placed between the superstructure and substructure. Jacking platforms were built onto the top of the piers to allow for easy replacement of bearings, if required after an earthquake.

California's Bridges: Benicia-Martinez Bridges across the Carquinez Straits (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.