New San Francisco Bay Bridge

For the engineering-minded reader, here is an interesting article on the new San Francisco Bay Bridge that is being built (a new Eastern portion that is, between Yerba Buena Island and Oakland).

You may remember that the last one had a section of the upper deck collapse in the 1989 Loma Prieta quake. This one is designed to withstand the greatest lateral displacement expected from a quake in the next 1500 years. And what fascinates me is one of the key features, “sacrificial sections of weaker steel” that will absorb the energy, sparing the rest of the structure. These are 60 foot long sliding steel tubes at the joints, and hinge plates that connect the four shafts that make up the single tower of the suspension bridge portion. I immediately thought of how Indy cars are designed to shed pieces in an accident, to bleed off the energy–this seems to be the same principle. Unlike an Indy Car, though, if the hinge plates are deformed in an earthquake, the bridge will still be operational–they’ll still be strong enough to hold the sections of the tower together, and can be replaced at greater convenience, without shutting down the bridge.

That is so cool.

About J@m3z Aitch

J@m3z Aitch is a two-bit college professor who'd rather be canoeing.
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9 Responses to New San Francisco Bay Bridge

  1. Matty says:

    This one is designed to withstand the greatest lateral displacement expected from a quake in the next 1500 years.

    Now that’s forward planning.

  2. James Hanley says:

    Heh. Of course the bridge itself is only designed to last 150 years, but that greatest lateral displacement could happen tomorrow just as well as on February 11, 3512,

  3. Matty says:

    Of course, I’ve had to explain the basic principle a few times. In 2009 we had heavy snow in December, the odds of which were 1 in 30* and any number of people announced that it wouldn’t happen again for 30 years, then in 2010 we had heavy snow in December and they declared the odds must be wrong. The idea that if the risk is 1in 30 then it is 1 in 30 every year regardless of the recent past just didn’t seem to compute.

    *I realise we are actually dealing with a moving average and the overall odds can change but I’ll still maintain that snow in 2009 did not itself alter the likelihood of snow in 2010

  4. James Hanley says:

    It’s like flipping a coin. If you flip heads 8 times in a row, most people will believe it’s more likely to turn up tails the next time.

    Of course half the time they’ll be “right.” If not, they’re even more sure on the 9th time it will be tails. Sooner or later, they’re always proved “right.” ;)

  5. Lance says:

    “Sooner or later, they’re always proved “right.” ;)”

    Confirmation bias is one of the most insidious problems facing human perception. Even scientists have to make sure that they construct falsifiable hypotheses and rigorously evaluate the evidence. If your hypothesis is plastic enough to explain every possible outcome it really explains nothing.

    The bridge article reminded me of the failure of the Tacoma Narrow bridge “galloping Gerty”.

  6. James Hanley says:

    Speaking of confirmation bias, I saw a church sign yesterday that said “P.U.S.H.–Pray Until Something Happens.”

    Unless I badly misunderstand how the world actually works, I’m pretty sure that sooner or later something is bound to happen.

  7. Lance says:

    You can’t falsify prayer. If the requested action happens this verifies the prayer. If it doesn’t, well then it’s just not part of “God’s plan” or God is “testing” you.

    Even at six years old I knew this was nonsense. I just pretended to believe because I was afraid to admit that it didn’t make sense to me. It was very disturbing that everyone around me seemed to be buying into this craziness.

    When I was twelve year’s old I remember reading Bertrand Russell’s essay “What I believe”. It was exhilarating and liberating to realize that other people felt the same way about this lunacy. Still, I kept my thoughts to myself but I no longer felt guilty that I didn’t share the faith of my family and friends.

    I felt empowered. I felt like my “tribe” was out there somewhere and it was only a matter of time until I joined them.

  8. James Hanley says:

    Of course you can’t falsify prayer–that proves prayer is for real!

    (No, no, don’t jump on me. I’m just funnin’.)

  9. Lance says:

    The Lord said, I believe it, that settles it!

    (An actual bumper sticker.)

    Sadly many of the people I know think this is sound logic.

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