Tuesday, January 21, 2014

What goes up, must come down

It's now been 6 months since the new Bay Bridge went into operation, so it's time to take the old bridge down.

Wired has a nice survey article: The Dangerous Art of Tearing Down Bridges, Dams, and Aircraft Carriers.

The piers of the cantilever truss aren’t holding the bridge up. They’re holding it down. “This is like a highly strung bow,” says senior bridge engineer Brian Maroney. (A bow made of 50 million pounds of steel.) “You don’t want to just cut the bow because the thing will fly off in all directions.” So crews will first remove the pavement on the upper deck to lighten the bridge’s load and reduce the tension. Next they’ll isolate steel supports, jacking them out of tension until they can be cut without whipping apart. Then they’ll slowly release the jacks.

The SF Chronicle has another nice article: Demolition crews start chipping away at old Bay Bridge

All told, demolition crews will remove 58,209 tons of steel and 245,470 tons of concrete that make up the 1.97-mile eastern span. The contractors will determine where the crushed and twisted remains of the bridge end up, Gordon said. Most will probably be either recycled or reused. Some pieces may be saved for a park planned at the eastern end of the bridge so people have something from the old span to remember.

Interestingly, even though this is a 300 million dollar project (at least) and will take 3 years (at least), it is a lot harder to find up-to-date status information about the demolition project, beyond high level summary documents.

I guess people aren't as interested anymore. Just cut it down and get it out of there.

A number of older bridges across the San Francisco Bay have been removed in recent years, most notably the old Carquinez Straits bridge.

Soon, the East Span will disappear.

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