Friday, May 25, 2012
New Bay Bridge Progress
Idon't think about the Bay Bridge very often; I don't drive much anymore, when I do it's very rarely into San Francisco so it's generally only when I see the bridge from West Oakland or the hills that I think about it at all. But on Wednesday I took part in a special tour of the bridge with the local chapter of the Society for Industrial Archeology. A very knowledgeable CalTrans PIO named Vic showed us a short video and answered questions, then took about 25 of us out on a boat to see the old and new east spans up close and personal.
It may seem like ancient history to recent Oakland residents, but it was almost 25 years ago that the Loma Prieta Earthquake destroyed the Cypress structure in West Oakland and damaged the Bay Bridge. A 50-foot section of the upper deck collapsed, leaving the vital link in Bay Area transportation impassable for a month and half.
Part of why it's taken so long for the project to be completed is that it's actually several projects. Besides building the new east span, they also needed to retrofit the west span, rebuild the San Francisco approach to the bridge, and temporarily retrofit the existing east span so that the bridge could remain open while the new span is being built. The new east span is made up of an approach in Oakland, the skyway, the signature suspension span, as well as the transition on Yerba Buena to the existing two-layer tunnel.
And part of why it's taken so long is that as vital as the bridge is, CalTrans and various contractors have done a lot of work to try to ensure the updated bridge won't fail again, and that has required inventing some new ways of building bridges. For example, the skyway has a number of large joints connected by hinge-pipe beams. They look like huge dowels, and each can make small moves with temperature changes and large moves in an earthquake. In the event of a really large earthquake, the center of each 'dowel' is designed to break to keep the structure of the bridge intact. The joint can then be replaced. Similarly, the tower of the Self-Anchored Suspension (SAS) span has shear link beams between the four legs. The beams are designed to flex in the event of an earthquake, and can be replaced if damaged.
It was a fascinating tour, and a nice chance to see the old east span as well as the progress on the new. Unlike a lot of people, I actually like the old span. If I had the money, I'd get the Oaklandish t-shirt of it in a flash. (Well, and a half dozen others like Typehoods, Train Tracks, Silver Skull, Sugar Skull, Cranes Reflection, and East Oakland signs, if somebody is feeling generous.) But seeing it first-hand, I'm impressed with the design of the new span. It's got clean, elegant lines, though those are harder to see with all the falsework (temporary supports), a unique asymmetrical design, and features for everyone from pedestrians to nesting cormorants.
Lots more pictures from the tour:
For the latest updates on the Bay Bridge project, and more pictures and video, check out the Bay Bridge Info website. They've also got some great photos and other items from the construction of the bridge and the celebrations for the opening in 1936.
The slideshow includes a picture of the "Bay Bridge Troll" on the existing east span that was installed by ironworkers repairing the collapsed section of the upper deck. For a closeup picture of it and more info about it, see the Wikipedia page.