Author Topic: bridge collapsed (Read 1101 times)

Spikes · « **Reply #30 on:** August 03, 2007, 07:25:24 AM »

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Originally posted by Maverick
The folks on the ground haven't even had a chance to look at the situation yet and as usual the AH armchair experts have already determined the cause.

lol! nice

Odee · « **Reply #31 on:** August 03, 2007, 07:59:59 AM »

Within this article related to the recent bridge collapse in Minneapolis, the FBI has included some good reminders about scams and e-mail attempts to solicit money from individuals.

FBI Statement On Minneapolis Bridge Collapse
Thu, 2 Aug 2007 15:00:00 -0500

Regards,

cav58d · « **Reply #32 on:** August 03, 2007, 03:57:00 PM »

What happened is extremely sad and tragic, and my heart goes out to all involved...

However, the news is taking it a little far. I havent been able to turn on any cable news station since this has happened without seeing the same aerial picture of the bridge, and retarded reporters all saying the same thing....

This post has nothing to do with the tragedy, more of how tragic it us about our media.

Dichotomy · « **Reply #33 on:** August 03, 2007, 04:15:54 PM »

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Originally posted by Rolex
I would put over half a century of winter salt from the roadbed leaching through joints in a span higher on the list of possible causes than errors in structural calculations. But hey, what would I know? You're the student who knows everything.

I'd be really interested in reading the final report. I'm not a trained structural engineer but circumstances have forced me to learn a LOT about it. Now I find the subject fascinating.

My heart goes out to the families of the people who were lost.

PS lasersailor184

what kind of engineering are you studying?

lasersailor184 · « **Reply #34 on:** August 03, 2007, 07:48:49 PM »

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Originally posted by Dichotomy
I'd be really interested in reading the final report. I'm not a trained structural engineer but circumstances have forced me to learn a LOT about it. Now I find the subject fascinating.

My heart goes out to the families of the people who were lost.

PS lasersailor184

what kind of engineering are you studying?

Architectural Engineering. I have roughly a semester and a half worth of structural analysis, and structural design under my belt. But I've decided not to pursue structural engineering.

I'd be interested in seeing the second video of the collapse. From what I can guess at from the first video, it appears that the bridge sheered off at the close end of the bridge. This is odd because more often then not structures' sheer strength is multiples higher (3-5x) then the standard sheer stress encountered.

Basically, if it was a moment failure, meaning the bending failure, it would have snapped in the middle where the moment stress is the highest. But again, from what I can see from the video, it doesn't snap in the middle.

Dichotomy · « **Reply #35 on:** August 03, 2007, 10:35:37 PM »

ya I've seen the video too and I agree that it should have failed at it's weakest point

A little background here I've been in the light pole and cell tower business for the past 12 years. When I hired on with my current employer they didn't have any ties to any engineers. I have a lot of ties to engineers so bam they buy me a design program and now I design light poles. Remember that when you drive down the highway or go to a sporting event and be afraid

I'm by no means an expert in bridge design but being exposed to AASHTO in all of its variations, UBC, CBC, FBC, etc.. on a day to day basis you tend to pick a few things up.

I'm wondering if the bridge might have had a low grade harmonic vibration in it that wasn't picked up during inspections that might have led to catastrophic failure.

I'm almost certain there's a certified structural enginerd or two on this board that might have an opinion on this.

You sure you don't want to do structural engineering? Get about 30 seals and you can make bank sitting on your butt stamping the work I do

lasersailor184 · « **Reply #36 on:** August 03, 2007, 11:23:25 PM »

Well, if it was a collapse due to sheer stresses, then it did collapse at the weakest point. Shear stresses are constant from column to column, assuming the weight is spread out evenly. It would take a really heavy point load or two for this assumption to not stand for something the size of the bridge. These point loads would be a lot heavier then anything on the road.

The harmonic theory could be a good one. The correct loading and just the exactly right speed of cars driving over could over load any connections that may be rusted out from weathering. But then my experiments with physical harmonics is lacking compared to experience with electrical harmonics.

The structural part wasn't so bad, but I can hardly sit still. Working constantly at a desk drives me crazy.

Holden McGroin · « **Reply #37 on:** August 03, 2007, 11:46:22 PM »

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Originally posted by Dichotomy
ya I've seen the video too and I agree that it should have failed at it's weakest point

I can say that the weakest point failure mode is a certainty, knowing nothing else about the bridge.

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I'm almost certain there's a certified structural enginerd or two on this board that might have an opinion on this.

I am a registered mechanical engineer, but because I have not seen the prints and reviewed the as builts or the maintenance records, I have no professional opinion on this.

Perhaps a few months and much data and someone somewhere may come up with the answer. Any opinion given in the first few days is quite probably incorrect.

Dichotomy · « **Reply #38 on:** August 03, 2007, 11:52:58 PM »

I should have stated 'theoretical' weakest point. From the film it doesn't look like it initially failed at midpoint which is, assumption on my part, where the load stresses are the greatest.

I agree holdin that it's all uninformed conjecture at this point but it never hurts to move the brain cells around. Especially my besotten ones

Laser.. wait till it hurts to get up and you might change your mind

bj229r · « **Reply #39 on:** August 04, 2007, 09:32:23 AM »

Would be safe to assume all the 'missing' were lost, but thankfully, the original estimate of '20 missing' has been downgraded. Could have been FAR worse

blame....looks like a 'Katrina II' is in the brewing

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Senator Patty Murray said that Bush has not supported Democrat efforts to increase spending on critical infrastructure....

...A state senator blamed the previous republican governor for not supporting tax increases (though Minnesota had a tax surplus of some 2 billion)--didn't seem to stop the projects for the new stadiums...

CNN's Jack Cafferty said if we weren't spending all this money in Iraq these people wouldn't have died....

Modern human nature at work here---SOMEtimes bad watermelon happens to good people, it doesn't ALways have to be somebody's fault

lasersailor184 · « **Reply #40 on:** August 04, 2007, 02:12:22 PM »

Quote

Originally posted by bj229r
Would be safe to assume all the 'missing' were lost, but thankfully, the original estimate of '20 missing' has been downgraded. Could have been FAR worse

blame....looks like a 'Katrina II' is in the brewing

...A state senator blamed the previous republican governor for not supporting tax increases (though Minnesota had a tax surplus of some 2 billion)--didn't seem to stop the projects for the new stadiums...

CNN's Jack Cafferty said if we weren't spending all this money in Iraq these people wouldn't have died....

Modern human nature at work here---SOMEtimes bad watermelon happens to good people, it doesn't ALways have to be somebody's fault

Like that one Southpark episode. Something akin to: "Beaverton only has a population of 8,000 people, however we are REPORTING that casualties are in the millions."

Hornet33 · « **Reply #41 on:** August 04, 2007, 05:36:12 PM »

Quote

Originally posted by bj229r
Would be safe to assume all the 'missing' were lost, but thankfully, the original estimate of '20 missing' has been downgraded. Could have been FAR worse

blame....looks like a 'Katrina II' is in the brewing

...A state senator blamed the previous republican governor for not supporting tax increases (though Minnesota had a tax surplus of some 2 billion)--didn't seem to stop the projects for the new stadiums...

CNN's Jack Cafferty said if we weren't spending all this money in Iraq these people wouldn't have died....

Modern human nature at work here---SOMEtimes bad watermelon happens to good people, it doesn't ALways have to be somebody's fault

Yeah but this is America here. Everything bad that happens is SOMEONES fault. Most of the time not even the fault of the person that did something wrong. FOX news pissed me off the other night. Flipped channels and there they were with a huge banner on the TV, "Bridge collapse...Who's to BLAME?" This was less than 24 hours after the event. Mainstream media really pisses me off when stuff like this happens.

Ghosth · « **Reply #42 on:** August 05, 2007, 08:06:13 AM »

I'm guessing here but I'm going to step out on the plank and make a prediction.

Bridge was examined 2 years ago for stress cracking, found some, but didn't think it was bad enough to do anything about it.

Take a stress crack which opens the steel to the elements ie no paint coatings to prevent rust. Add in a highly corrosive winter enviorment with all the salt/chloride they use on the roads and you have a bridge beam thats going to fail. Question is when not if, and where.

Video I saw showed one side bumper to bumper for 2 lanes maxing out the load the bridge can carry. The beam that did go first will be found to be in a place almost impossible to inspect well.

bj229r · « **Reply #43 on:** August 08, 2007, 10:43:25 PM »

Some news: link

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Potential Flaw Is Found in Design of Fallen Bridge
By MONICA DAVEY and MATTHEW L. WALD
MINNEAPOLIS, Aug. 8 — Investigators have found what may be a design flaw in the bridge that collapsed here a week ago, in the steel parts that connect girders, raising safety concerns for other bridges around the country, federal officials said today.

The Federal Highway Administration swiftly responded by urging all states to take extra care with how much weight they place on bridges when sending construction crews to work on bridges. Crews were doing work on the deck of the Interstate 35W bridge when it gave way, hurling rush-hour traffic into the Mississippi River and killing at least five people.

The National Transportation Safety Board’s investigation is months from completion, and officials in Washington said they were still working to confirm the design flaw in the so-called gusset plates and what, if any, role it had in the collapse.

Still, in making public their suspicion about a flaw, the investigators were signaling they consider it a potentially crucial discovery and also a safety concern for other bridges around the country. Gusset plates are used in the construction of many bridges, not just those with a similar design to the one here.

“Given the questions being raised by the N.T.S.B., it is vital that states remain mindful of the extra weight construction projects place on bridges,” Secretary of Transportation Mary E. Peters said in a statement issued late today.

Concerns about the plates emerged not from the waters of the Mississippi River here, where workers have only begun to remove cars and the wreckage with cranes, but from scrutiny of the vast design records related to the steel truss-type bridge.

In Minneapolis, state transportation department officials seemed stunned by the sudden focus on the bridge’s gusset plates, which are the steel connectors used to hold together the girders on the truss of a bridge. On this bridge, completed in 1967, there would have been hundreds of them, officials here said.

egads, this could mean that new taxes arent in order

lasersailor184 · « **Reply #44 on:** August 09, 2007, 07:05:19 AM »

Yes, everyone is jumping on the blame everyone bandwagon. I can't say that I was surprised when NPR blamed little susie that lives down my street.

Can't say that I've dealt with gusset plates at all. Most of the trusses that we use are premade. The only thing I can think of would be tear out or buckling due to the plate being too thin.