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What Happened To the Bay Bridge?
farnsworth writes "Tony Alfrey has put together a fascinating page with some history, analysis, and possible explanations for what ultimately went wrong with the recent emergency repair of the San Francisco-Oakland Bay Bridge. The bridge has been closed for days and is not scheduled to open for days to come, hugely inconveniencing more than 250,000 people a day. His analysis touches on possibly poor welding, a possibly flawed temporary fix, and the absence of a long-term fix or adequate follow-up by Caltrans, the agency responsible for the bridge. Slashdot is a great engineering community; what other insights do you have on the bridge situation?"
McSweeny's has a great article on this, broad reaching in its investigation of the many problems at hand. One thing that troubles me: I have seen many times in the California University and Transportation groups, failure to use earthquake retro-fit funds - they simply use them elsewhere. Its only when a problem like this arises that we learn they have not been used.
As a hobbyist welder, and someone who has worked with welders in an industrial setting, I strongly doubt that the welding is the culprit. "Faulty welding" doesn't happen on something of the scale of a bridge. If it's one welder working, maybe. But this bridge repair would have had dozens of welders working. No one person's welding could have broken a bridge. Sure, they were under a time crunch, but that doesn't result in shoddy welds. It means more welders are put on task. Those guys are trained and certified and their work is defined by specs that they follow and then is inspected by city or state engineers. If the welding is the problem, it means the original spec was faulty.
Seth
$5 / month hosted VPS on linux = awesome!
At least when they found the flaw they recognized the danger and attempted to fix before the bridge fell down.. The I35 bridge gusset plates were seen years earlier to be warping and this clue was missed.
No, Slashdot is mostly made up of computer janitors.
I do get that feeling now and then.
Many years ago, I went to a serious engineering school. There, the final exam in a course in structural engineering was this:
At the final exam, each student had to design a link to attach two pins some distance apart. There were obstacles between the pins and the link had to go around then. The design was to be for a specified grade of aluminum and had to support a specified load. Students knew in advance what the exam would be, except for where the obstacles would be. For the exam, you sat at a drafting table, and turned in a drawing.
The link you designed was then machined out of aluminum by a machinist. It was put in a testing machine and placed under the specified load. If the link broke, you failed the course.
If the link didn't break, it was weighed. Lower weights yielded higher grades for the course.
This is how good structural engineers are trained. (I'm not one. I was in EE/CS, and we had a different make-or-break exam.)
Depends on the rate of return you can get on other investments.
True story. I had a guy working for me who applied for a loan on a sailboat. This was a non-profit, so there were a lot of rich kids doing the noblesse oblige thing. Anyhow the bank calls, and afterward the guys says, "they turned me down".
"Why?" I asked.
"They screwed up. They said I didn't qualify because my income was only 40K."
"I don't pay you that much," I said.
"Actually 40K is my bi-weekly income, but I wanted to get a loan because my investments are returning higher than the loan interest rate."
What you want is the net value of the United States to increase as much as possible. You want the debt to go down relative to that figure. No major corporation *ever* tries to pay down all its debt. It would be insane, because they'd be paying opportunity costs. Just like my young friend, they don't worry about just one side of the ledger. They maximize their net worthy subject to whatever limitations liquidity puts on them. Naturally, this is not an option most of us ordinary mortals have.
What you really need to worry about isn't debt alone, but what you are using the liquidity the debt gets you to do. In other words, spending the money wisely. Spending on maintaining critical infrastructure *should* be a no-brainer. You don't say, "we're going to stop painting this very important bridge because we want to reduce our debt." That would be moronic. Likewise, even if you didn't have a nickel of debt, spending money on something that doesn't return anything is just as moronic.
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