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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.
I was under the impression that the bridge had to go through Yerba Buena not to serve the island population (who are only there because the bridge makes it convenient I imagine), but because the bay is too deep and without a firm bedrock to otherwise locate the middle section of the bridge securely.
Possibly that was only a concern when it was originally built, but regardless, you would essentially need to route it in the same path as otherwise you'd need a new landing point on the Oakland side and there's Alameda in the way.
In my experience most of the problems are in the northern half of D.C.'s Beltway. The area between D.C. and Baltimore might slowsdown but it never completely stops (except accidents of course). And Baltimore's beltway is good except for the area around I-83 (which is a poor design).
A couple times I've suggested extending I-85 up to Philadelphia and beyond, so as to provide an alternate route for traffic (especially truckers who are going straight through from Richmond-to-Philly without stopping), but neither the Congress nor the AAA seems to hear. Oh well.
"I disapprove of what you say, but I will defend to the death your right to say it." - historian Evelyn Beatrice Hall
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.)
The city is so nice and uncongested today. I don't own a car, so admittedly I am very biased, but I would be quite content just to leave the bridge closed. Plus it puts the focus on public transit, where a compact city like SF should be focused. For example, BART (the subway) is running 24 hour service this weekend. As strange as it may sound, despite being an urban environment we don't have 24 hour subway service normally!!!
This is what you call a rock-and-a-hard-place scenario.
Stuff suspended over people is the thing that gives the civil engineers I know nightmares. Closing a bridge like that gives traffic planners nightmares.
You put the two together, and there's a lot of pressure to do a little wishful thinking. That the emergency field repairs on the single most important piece of infrastructure in a major city are acting in an unexpected way is the kind of news nobody wants to hear. And so it's so easy to say, "well, we can't be *sure* what's going to happen, but what's the chance it's going to happen before we get a proper fix in?"
I can't help but think there might be parallels between the situation in California, where they're enduring a budget crisis that won't quit, and the situation as NASA where the goals stayed as ambitious as ever but the money was never there. As an engineer, I've been in situations where I've been ordered to do things for less money and time that is reasonable. And sometimes I've been successful, but even when I usually walk away from these scenarios *looking* successful, I *know* that I've left problems for the next guy that are going to cost a lot more than anything that could possibly be saved. And when management began to think of me as a miracle worker, I stopped functioning as a real engineer, because engineering is about cold, hard realities, not wishful thinking and trusting in luck (statistics, of course are a different matter).
God, if I were Scotty, I'd have fragged Kirk.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
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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Your comment is painfully accurate. Thing is, Slashdotters were a lot smarter when I signed up 8 years ago. There have always been Linux obsessives, conspiracy wingnuts, and kneejerk libertarians, but even they had something worth contributing now and then. There was a lot of stupid noise, but every once in a while you could have a really interesting and informative conversation with some random stranger. Now it's all just flames, rants, and temper tantrums.
I blame changes in the moderation system. Originally, the people who participated in Slashdot the most got the most chances to moderate. Then they changed the system to have moderators chosen solely from the middle of the usage curve, so that heavy users don't get to moderate at all. This means that moderators are sporadic users with no real investment in maintaining a real conversational community.
More recent changes in metamoderation are even worse. It's not really metamoderation at all, you just say you approve of the article or don't. Useless.
I've had a few email exchanges with Rob on the subject. He won't even listen to suggestions for minor tweaks, like making it harder to abuse the "overrated" and "underrated" mods. (You're only supposed to use these to counteract simultaneous mods, but you often see these as the only mods on a post; people use them to avoid being metamoderated.) He won't budge from his position that everything's fine.
I guess from a certain point of view, it is. Slashdot's traffic levels are bigger than ever, and it's probably the biggest profit center Sourceforge Inc. still has. (Sourceforge used to be OSDN, and before that they were VA Linux; the name changes represent a huge number of failed enterprises.) So Rob's first post-college job has brought him fame and fortune. What's not to like? But the original Slashdot community is dead, and I guess it's not coming back.
Oh, no mystery there. The Bay Bridge predates basket weaving degrees. ;^)
Even in the '50's and '60's engineering took precedence over politics. Today, being "politically correct" takes precedence over everything, except maybe generating revenue.
If at all interested in traffic engineering, consider speed limits. Real traffic engineers believed in the "85th percentile". In effect, when you open a new road, you post no speed limits - but you monitor how fast people go. After a period of time, you tally up those speeds, and settle on the 85th percentile. Faster drivers will almost all slow down to that speed limit, slower drivers tend to speed up closer to that speed limit, and everything flows smoothly. Today - speed limits are set well below that 85th percentile, intentionally. This way, when the cops are detailed to generate some revenue for the courts, they don't have to spend all day waiting for "x" number of speeders to come along.
If you want something totally screwed up, give it to a committee. If you want it FUBAR'd, make it a committee of politicians.
Anyway - the proper fix for that crack on the bridge would have been to shut traffic down, and REPLACE the damaged part. Slapping a band-aid on the problem was a political BS thing.
"Windows is like the faint smell of piss in a subway: it's there, and there's nothing you can do about it." - Charlie Br