Posted on 08/01/2007 4:28:27 PM PDT by ButThreeLeftsDo
Just turned on the news. 35W bridge collapsed in the Mississippi River. Cars, trucks, semis.....
Fires burning, tanker trucks, at least one school bus, more than ten cars......
Just now breaking.......
My wild a$$ theory.
There looked like there was a freight train that ran along the river and under the bridge at one point. The foundation that the piers stood on where constantly subject to vibration from the train and because these were not underwater they were not inspected as diligently.
The last train that was passing by cause the foundations to shake some more and finally let go.
Though interestingly enough, out of the 2 bridges in the pictures everything structural was visible on this bridge when you look at the old pictures. I was thinking that even without training exactly where I would put explosives if I were a terrorist but then they would be out in the open for anybody to see so once again it does not make sense.
That's a mild experience compared with crossing the Mississippi a bit west and upriver of New Orleans via the Huey P. Long bridge. That old combo railroad/auto traffic bridge is probably overbuilt in some ways, but the narrow lanes and scary old vertical-bar guardrails really crank up the pucker factor.
I believe it's currently being modified to widen the lanes and add additional lanes, and it's about damned time. I just hope those engineers triple-checked their math.
You will be hearing these words a lot in the coming days.
Corrosion and Fatigue.
Are you addicted to the Valium yet? ;^)
that describes Shep’s performance last night on Fox to a “T” LOL
LOL, haha
I actully thought Shep did pretty good.
When the superstructure supports, the steel that supports the road bed fails, the roadbed takes on significant stress. The stress will be distributed in that sheet as tension and compression.
The roadbed is a sheet of reenforced concrete. Where there's tension, and the stress rises to the breaking point, the concrete simply cracks and the rebar yeilds. Where there's compression, and the stress hits the failure limit, the concrete "explodes". It pulverizes and shoots out with all the energy that was contained in the concrete at that location, prior to the failure. IOWs, the static potential energy contained in those portions of the sheet that were under compression, was released as kinetic energy in the form of flying concrete dust and the shock wave created by that release. Those areas that failed in tension, simply crack, with the energy going into movement of the large broken sections and the shockwave created by the propagation of the crack.
In this case, the steel had yielded prior to the catastrophic failure. Regardless of what the rat politicos said in the various interviews. The engineering reports noted cracks in the steel. Cracks in the steel are never simply cosmetic. Cracks in the steel only occur when stress is applied. Cracks in mild steel, as is the case here, indicate fatigue, which is a microscopic rearrangement of atoms that aligns and separates grain boundaries in the steel "along the crack". That means the steel can not support what it originally could and the roadbed, the reenforced concrete sheet, now contains a considerable stress pattern that the sheet was never intended to contain.
The various interviews all say the roadwork was simply cosmetic resurfacing. That was not the case. The concrete sheet was being hammered and cut. That action caused the stress contained at those points to be redistributed to other intact areas of the sheet, so that those areas hit their failure limit. Once the sheet gave, it redistributed the forces on the fatigued steel of the superstructure, which was already stressed close to breaking(it had already began to crack), and the whole thing went down.
Neither the engineers that inspected the bridge, or the ones hired to do the repairs had any appreciation for what they were working on. The proof is in the water.
There has to be more than that.
Heard this morning that 20 families are awaiting news of missing kin. There must be some vehicles that were carried downstream or are under the rubble in the water.
The only way to determine the cause is forensic analysis of the evidence. Everything else is pure speculation and deserves no emphasis.
Nevermind, maybe it does make sense. Only have to take out one pylon to take out the whole bridge post 1919. LOL, I won't tell where I though was the best place to put explosives with an untrained mind and he found this info on the internet.
Just like I thought no demolition expert needed.
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