Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (1)

February 2014 (38.0240, -121.7516) Antioch Bridge

We are leaving Solano County today to look at the bridges to the south in Contra Costa County (see map below). Many of the biggest bridges cross county lines. For instance, today's Antioch Bridge (28 0009) crosses the San Joaquin River between Sacramento and Contra Costa Counties.

The Antioch Bridge is a toll bridge that was built in the 1970s and so it wasn't originally a part of the state legislative mandated retrofit program. Eventually Caltrans decided to analyze it, and like many other 1970 era bridges we found it was designed for too low a seismic load.

The retrofit included isolation bearings between the superstructure and the substructure and cross-bracing between the columns. We'll take a closer look at this interesting bridge tomorrow.

Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Solano County, California Bridges: Rio Vista Bridge across the Sacramento River

January 2014 (38.15899 Degrees, -121.68393 Degrees) Rio Vista Bridge 

Continuing to the east of the Benicia Martinez Bridges is the Rio Vista Bridge across the Sacramento River (previously visited in May of 2010). This is the last bridge in our survey of Solano County bridges. It's a 2890 ft long vertical lift bridge that was built in 1944. It includes a 306 ft long Warren truss lift span across the river channel.

The Rio Vista Bridge is on State Route 12 (in the town of Rio Vista) and the bridge gets raised and lowered a lot, which can back up traffic for miles. The bridge tender was nice enough to let us into the bridge house so we could watch him raise and lower the lift span.

This bridge got an extensive seismic retrofit in the 1990s that included lead-rubber isolation bearings supporting the approach spans (see photo above) and viscous dampers that were placed transversely to allow the tower to rock if the anchor bolts were to break (see photo below).

Sacrificial expansion joints were used to accommodate large longitudinal movements. Also cable restrainers were placed in front of the counterweights to prevent them from swinging into the towers (see photo below). Thus, the retrofit allows movement and damage while preventing a collapse for the maximum credible earthquake. For a more moderate event, the retrofit may allow the structure to remain in service.

Solano County, California Bridges: Rio Vista Bridge across the Sacramento River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Solano County, California Bridges: Benicia Martinez Bridges across Carquinez Strait

January 2014 (38.0424 Degrees, -122.1225 Degrees) Benicia Martinez Bridges

At the east end of the Carquinez Strait are the three Benicia Martinez Bridges (carrying I-680 between the cities of Benicia and Martinez). The photo above shows the new northbound Benicia Martinez Toll Bridge, a segmentally constructed prestressed concrete box girder bridge. I'm standing on the north side of the Strait photographing this bridge with a telephoto lens that considerably foreshortens the bridge. In the background is an oil refinery that includes a terminal in the Strait for tankers to offload their oil.

Besides the new northbound bridge, there is an old steel truss bridge that was retrofit with giant friction pendulum bearings in the 1990s (see photo below). These bearings reduced the inertia load to the piers and foundations, saving Caltrans the expense of retrofitting the foundation. Both the northbound bridge and the southbound retrofit are part of just a handful of bridges designed to remain in service after a large earthquake.

I had forgotten that we had once practiced our rope climbing techniques on a reinforced concrete leg of the retrofitted bridge (before the new bridge was built). The columns were so tall that we had to tie two static lines together and got to practice climbing above and below the knot as well as how to move from side to side around the column.

Between the northbound and southbound bridges is an old (1930) railroad bridge that still gets plenty of use from the BNSF, UP, and Amtrak trains that cross it every day. The bridge includes a lift span over the shipping channel. In fact, there were so many trains, that it was a hassle while they were trying to work on the retrofit because they had to clear the tracks every time a train came by. The photo below shows the railroad bridge before the northbound Benicia Martinez Bridge was constructed. A better view of the railroad bridge was in the June 5, 2001 blog.

Solano County, California Bridges: Benicia Martinez Bridges across Carquinez Strait by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.