I find it irritating that the San Francisco Chronicle uses Caltrans as a scapegoat whenever a ship collides with one of our bridges. They claim that the resulting oil spill is due to Caltrans not employing enough collision protection on our bridges. I don't think there is any protection if a large vessel is traveling over 10 knots.
This bridge got a seismic retrofit in the 1990s. I think that most bridges were retrofitted in the closed position since they are only opened a few times a day (the opposite for railroad bridges). This retrofit employed lead rubber bearings for the approaches and viscous dampers at the towers (in case the anchor bolts broke). I believe there was also something done to keep the counterweights from swinging into the towers during an earthquake.
Movable Bridges - Rio Vista Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.