Interesting video about the building of the new Bay Bridge in process

[lunatica]

in the Bay Area. Drivers and cyclists will actually have an unencumbered view of the Bay Area while driving on it. The way the old Bay Bridge was built no one could see anything while driving. I think it's going to be a very nice looking bridge.

http://baybridge360.org/#/poi/sfobb_overview

[BrklynLiberal]

1. Thks.

[madrchsod]

2. to bad the knuckle heads who designed our two bridges did`t think of that

the railings on the two new bridges that cross our scenic river block the view. we built an excellent 2 million dollar waterfront park that can`t be seen from the bridges.

the new bay bridge will be spectacular!

[lunatica]

3. kick

[Xithras]

4. Just pray you're not on it in an earthquake

The engineers designed it to be deformable so it will survive a major quake. The good news is that it shouldn't fall down. The bad news is that the road deck will literally be bending and flexing beneath your car, and the expansion joints will be opening ans slamming shut, while you're trying to drive across that beautiful span...with only the low siderails standing between you and the murky Bay water 100 feet below.

The real joy will be on the suspension section. Nobody has ever attempted to build a self-anchoring suspension bridge in an earthquake zone before. Unlike regular suspension bridges, this one won't be attached to the ground or the bridges on the other side at all. It essentially "hangs" by its cables from its central tower, and its mass will keep it in place. The earthquake simulations show that it's going to buck like a wild horse in a quake though. Whee!

[lunatica]

5. Do you have a link to the earthquake simulation?

I'm picturing the trailer from the movie "2012" with John Cusack.

:scared:

[Xithras]

6. No, it was several years ago that I was reading about it.

The thinking of the engineers was essentially that it's OK for the bridge to bend and buck around all over the place, so long as it stays above the water. It's OK to lose a couple of cars over the side to flex and roll, if doing so keeps the structure up and the thousands of other cars on the bridge out of the Bay. They may be right in that assessment, but I gurantee that the drivers on the bridge will be wishing for those view obscuring high guardrails when the Big One hits :)

The bridge is actually designed so that each prefab section can flex up to 3 feet without failing, and the entire bridge could shift something like 15 horizontal feet over its entire length without collapsing, or be shortened or stretched up to 3 feet over its span without the bridge buckling. It's a feat of engineering, but it would be terrifying to actually be ON the bridge when that happened.

Here's a video simulation of the new bridge in a quake. It doesn't go into the numbers, but just look at the deck flex! http://www.facebook.com/video/video.php?v=1251601616789

Of course, not everyone agrees. There are entire websites dedicated to slamming the project, most prominently http://www.oaklandbridge.com/. If you visit the Questionable Seismic Safety link at the top of their menu, you can read a paper by a UC Berkeley Structural Engineering prof describing how he suspects that the bridge will simply collapse in a major quake. CalTrans doesn't pay him much attention, and maybe you shouldn't either, but the love for the bridge design is hardly universal. I personally don't understand why they simply didn't build another conventional suspension like the western span.