September 2008 Archives

Bridge by Boat

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This month is Architecture and the City month in San Francisco, and on Thursday, Noel and I took a boat tour of the Bay Bridge construction offered by the AIA.

Unless you take the ferry a lot, you likely do not get this sort of view of the Bay Bridge. The tour was totally sold out, and I think they could have done another one, easily, given the number of people I know who wanted to go but couldn't. And only a little over half the people there were architects or engineers.

Looking at the Bay Bridge

Some people who are not very good with history or current events have mentioned to me that they thought it was stupid that they were replacing a perfectly good bridge at great expense. To them I must point out this image, courtesy of the USGS, of that "perfectly good bridge" in October, 1989.

Bay Bridge, collapsed

They've patched the bridge up, obviously. I go over that bridge a couple of times a day on my way too and from work. But if you're not nervous on that bridge, you have never heard a Caltrans engineer tell you what sort of foundation it has.

Get this: this bridge, over which hundreds of thousands of people pass daily, is on wooden piers that run only about ninety feet into the soft Bay mud. It's like a bridge built on a foundation of steel-reinforced pudding. It might sound strong, but it's worth nothing whatsoever.

That foundation is the reason why the bridge could not be upgraded: it would cost many times more than the new bridge, and the upper portion would still need upgrades, too.

Where the bridge broke

Anyway, that's the reasons why they're replacing the bridge, so let's get out on that boat tour.

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