Saturday, August 04, 2007

 

Falling Bridges

Besides serving their obvious purpose, bridges are often beautiful.

One of my favorite bridges is the Roebling Bridge in which crosses the Ohio River from Covington, KY to Cincinnati, OH. It opened in 1867 and was the prototype for the Brooklyn Bridge. (It is NOT a copy of the Brooklyn Bridge. It pre-dates the Brooklyn Bridge.) My kids call this the "singing" bridge because of the sound from the steel grate road surface as tires roll across it.
Another is the Simon Kenton Bridge which crosses the Ohio River at Maysville, KY. Being the younger of the two bridges, the Simon Kenton Bridge opened in 1931. Traversing it in a large vehicle can be a tight squeeze.

Both these bridges are still standing and functioning well. The Simon Kenton Bridge underwent major repair and re-construction just a couple of years ago, which required it being closed for 18 months.

Now, we need to ascertain why the bridge fell in Minnesota. Some have already started blame game. I agree that it is probably Kevin Bacon's fault but let us not rush to judgment. (Hat tip to Instapundit.)

What are the contributing factors in a bridge collapse? Guess what? I really don't know. They could be myriad, some unforeseen. Age could be a factor as metal fatigues and other materials deteriorate. But, as we can see from the two bridges above and from ancient Roman construction, many bridges far outlast the I-35 bridge.

Could the bridge design be faulty? Bridges do fail because of faulty design. The Silver Bridge collapse in West Virginia, the bridge collapse dramatized in "The Mothman Prophecies," fell primarily because of faulty design. Tacoma Narrows Bridge gave us one of the most dramatic bridge collapses due to design flaws. (The link includes video of the collapse.)

Maybe the design was fine, but it wasn't followed during the construction as in the Kansas City Hyatt Regency disaster. Construction companies don't always build everything to specifications.

Maybe the land on which the bridge was built wasn't steady or solid enough. Maybe the current construction workers on the bridge did something they shouldn't have. Maybe we should wait until a thorough investigation is done before we start pointing fingers.

In the mean time, it wouldn't hurt to double check some other bridges and renew our commitment to maintaining our infrastructure, more than just our bridges. (Hat tip to Instapundit, again.)

Comments:
maybe the old bridges were built with tolerances to the traffic, the modern couldnt cope with the amount of traffic. the older bridges used to be over built.

if they said use 1 ton strand they would use 2 or 3.. they built them to last. over engineering them, now its put up fast get money and get out..

plus all the other reasons you have given
 
You probably have a point. The designers of the two old bridges pictured would have had to been prophets to have had any idea of the level of future use of these bridges. But the bridges do just fine. The tolerances were far beyond what the designers could have reasonably expected.
 
Evidently, a train was going under at the same time that the workmen were jack hammering above. Resonances?
 
Resonance is what brought down the Tacoma Narrows Bridge. It could have contributed.

Last night I watched Geraldo for abut 5 minutes (all I can take at a time). He showed some pictures of some supports seriously out of line. Or, at least it appeared so to the me, but I'm not a structural engineer.
 
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