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Bay Bridge: How will it do when the Big One hits?

By dcuff
Tuesday, October 13th, 2009 at 3:25 pm in Bay Bridge, Bridges, Caltrans, Freeway collapse.

We all remember the scary images of a section of the Bay Bridge upper deck collapsing like a trap door 20 years ago when the Loma Prieta earthquake shook the Bay Area.

Now we can see how the new East Span of the Bay Bridge is expected to perform in a big earthquake. Caltrans has posted a computer animated video on its Web site – – depicting how a major earthquake will affect the new East Span, which is scheduled for completion in 2013.

 The new span will replace the original span, which was closed for a month after the Loma Prieta earthquake in 1989.

The two-minute video is fascinating. You see a bridge loaded with cars undulating in big waves. You see the cable supporting the suspension span moving about.

 The video is real as you can get in predicting how the bridge will perform in a major earthquake.

“We are not creating a horror movie,” Caltrans spokesman Bart Ney told reporters yesterday during a briefing.

 The video was based on scientists’ best estimate of how the bridge will respond to the most violent earthquake shaking expected to hit the bridge in a 1,500-year period.

Scientists say the new East Span will bend but not fail because of a design that makes use of metal fuses in key locations.  It will sustain some minor damage but not enough to keep it closed for more than a short time – maybe one or two days – as crews repair some deck damage, Caltrans officials predict.

And that’s what we the public are getting for the $6.3 billion new East Span.



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