Posted on 08/04/2007 11:49:45 AM PDT by kathsua
I've been looking at some of the video showing the collapse of the I-35W bridge over the Mississippi River in Minneapolis and it looks like the collapse could have resulted from a major mistake by the company working on the bridge's surface. The bridge carries eight lanes of traffic, four each direction. To maintain an even load on the bridge supports during construction the contractor should have either worked on the two inside lanes of both sides of the bridge or the two outside lanes. Instead the contractor worked on the inside two lanes of one side and the outside two lanes on the other.
The result was the support on the side in which the outside lanes were carrying traffic had to support a greater load than the side on which the inside lanes carried traffic. I'm oversimplifing, but essentially the support on this particular side would have been carrying the load of the traffic directly above it as well as a portion of the traffic on the other side. The support on the other side would only have been carrying a portion of the load on its side.
If you've watched videos from the scene you know there is a school bus and semi truck next to each other in those outside lanes. There is another semi just behind them. These heavy vehicles went across the supports just before the collapse. The supports on this side of the river shifted toward this side with the roadway shifting toward the other side as if the weight of the heavy vehicles may have been too much for it to carry in a weakened state
My background is in math and physics rather than engineering so I'm not familiar the precise distribution of weight and how the supports carried it, but the basic math would indicate more stress on one side of the bridge than the other.
A computer analysis of the remains of the bridge and its design will be necessary to determine the precise amount of stress on the different pieces of the bridge and their physical condition. This analysis will show exactly which part(s) failed. Fortunately investigators have a computer program using Finite Element Analysis developed at the University of Minnesota.
Is the myth supposed to be that (1) marching in step on a bridge is dangerous regardless of the bridge's design or composition, or (2) one or more bridges exists somewhere where marching in step could be dangerous. The former is almost certainly false, but the latter would be much more plausible. A reasonable exploration would be to try to build bridges that would be subject to resonant failure and see how badly one had to jinx the design to make that happen.
I wouldn't be that harsh. Carl Sagan's "Cosmos" wasn't the equivalent of serious study, but it inspired a lot of people to become the Ph.Ds they are today. Pop-culture lectures by Jane Goodall, or Robert Feynman, or Sagan, or Jacques Cousteau. or Robert Ballard, for that matter Teddy Roosevelt filled young minds with visions of worlds yet unexplored.
They may not have been the fastest runners or the highest jumpers in the Olympics of science, but don't underestimate the value of a good coach.
PS: Kari is every kind of hot there is, and think she invented a couple of new ones. Why aren't there more geek-girls like that, and nearer to me?
No, it's a coincidence that the bridge collapsed while someone was tearing the c%$p out of it.
Check here.
Also there is a very interesting inspection report dated June 0f 2006.
Check here .
Before the World-Wide Web -- or more precisely, the http protocol and the html language -- one of the most popular Internet protocols was called gopher. It allowed linked hypertext, searchable databases, and flexible data structures. It was ahead of its time for a few years before the Web caught up and passed it in about an hour and a half.
Gopher was so named for the Golden Gophers, mascot of the University of Minnesota. UMN was, along with UIUC (university of Illinois, Urbana-Champlaign), prominent in the early days of the 'Net. No big surprise that one of the pioneers of engineering models came from that same petri dish.
It only looked 17...
I agree that the instances you referred to were due to lateral forces as opposed to vertical forces. However, from a physics class where we saw not only footage of the Tacoma Narrows bridge collapse, but also watched footage of the tests done to identify the cause it was stressed that the Narrows collapse did not happen in high wind conditions, but medium wind force, about 40 mph. That was part of the mystery- the bridge had survived much higher winds. The tests done in the video led the researchers to the conclusion that the wind was a pulsating wind with a rhythm of sorts, but in gusts as opposed to a steady wind. The on again off again gusts supposedly caused the resonance that was blamed for the failure. I did not understand the explanation, but that was the one we learned in physics class.
I’m very glad your experience has been like that.
How do you think the “Big Dig” in Ma got to be such a money pit?
The conditions where very different from those shown or alleged to exist and the State told the contractors, sue me.
The claims continue, and the lawyers love it.
A bridge expert on one of the Fox shows confirmed what I thought I was seeing. the support on the end where the bus was not only shifted it actually rotated toward the right. It looks like the metal portion of the bridge support was on a concrete struture. Would rotation indicate that the support was disconnected from the concrete whatever caused the collapse or would it likely have already disconnected from the support and its rotation caused the collapse? Possibly it started to shift causing the roadway on the shore side to start falling and then push it the rest of the way.
The bridge was designed for anticipated traffic of 40,000 vehicles a day and was carrying 140,000 - 170,000 vehicles a day. Like most of the Interstate system is carrying much higher traffic than it was designed for which is why they have had higher maintenance costs.
Wow. He used to have a lot more hair.
I used to drive across the Tacoma Narrows Bridge frequently. (This was the bridge built after the collapse.) On one occasion during a strong, but not unusually high wind, the vertical cables on the bridge were vibrating like guitar strings. I have never seen this on any other suspension bridge, so I suspect there is something unique about that location that contributed to the accident.
They didn’t debunk they just didn’t think it was very likely to happen on modern bridges. However, if they had a larger driver to use it might just work. They were able to get the bridge to resonate pretty good though.
That is really interesting- and would really scare me!!
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Must've been all the face-lifts...
There's a little matter of American pride which the free market & the world recognizes.
That's why one will find US companies all over the world doing serious projects. Ya there's cheaper outfits, but when ya want the best....
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Never heard of The Big Dig, huh?
"BOSTON, July 28 (UPI) -- A company that admitted supplying substandard concrete to Boston's Big Dig has agreed to pay $50 million to settle the case.
"The project, already plagued by cost overruns and delays, became notorious when a chunk of concrete fell on a moving car, killing a woman."
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