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To: MNJohnnie

I see your point, however it is 40 years in a 2000 year old art.

We build silly bridges that load concrete in flexure (big horizontal beam, with the top section loaded in tension) Concrete is terrible in tension, it likes compression. So, we add steel tension cables to preload the span in compression. This works and keeps the entire cross section in compression. All is good until the steel fails (rust). The only reason we do this is architects hate arches. ...according to a CE friend of mine that builds bridges.

About the only thing we’ve added since the 60s is cost and some prefab capability.


112 posted on 08/07/2007 1:35:49 PM PDT by Dead Dog
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To: Dead Dog

You are saying steel is steel and we don’t know how to protect it better now then we did in the 1960s? That computer modeling doesn’t add anything to our understanding of how and why all the bridges that have failed since 1967 failed?

As someone who has been on and under this bridge that failed a bunch of times, I got to say, it sure looked like a poor design to me. Long spindly steel legs supporting a whole lot of concret WAY way way up in the air. However, not being an engineer I just always assumed they knew way more then me about their job.

So basically, what you are saying is it is bad design. That we could do a much better job?

Another question? How come my 1st car in the 1980s rusted so much and my current one doesn’t yet I have/had both the same amount of time? I assumed that meant we were better at protecting them now.


113 posted on 08/07/2007 1:45:15 PM PDT by MNJohnnie ("Todays (military's) task is three dimensional chess in the dark". General Rick Lynch in Baghdad)
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