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Overstressing a bridge

Overstressing a bridge

Overstressing a bridge

Just watched this video and was surprised about how much you can overstress some structural elements without causing failure:


RE: Overstressing a bridge

Nice video but it may not be overstressed. The bridge uses a shallow stiffening girder as opposed to a stiffening truss; that's why you see pronounced deflections.

Arkansas Highway Department has a website with old bridge plans; I'm going to look to see if this one is in there.


RE: Overstressing a bridge

bridgebuster, interesting link. Just wondering what is the oldest bridge in that list...

RE: Overstressing a bridge

Okiryu - I found that link a few years ago and downloaded some plans. A lot of stuff from the 30's; don't recall if I found anything earlier.

Here are the bridge plans:


A Wikipedia link:


RE: Overstressing a bridge

I thought a suspension bridge was supposed to deflect; otherwise, the beams would be carrying the load and not the cables.

We lived up in Colorado years ago and went up to the Royal Gorge bridge. I was talking to an elderly lady about that later, and she said back when they built it, the wind deflections would move the bridge enough that, standing at one end, you couldn't see vehicles at the other end. She said they added additional stiffening cables later. When we were there, watching closely, it looked it was slowly swaying up and down about a foot from the wind. You couldn't really tell it was moving when you were out on it.

When I was a kid, the bridge across the intracoastal canal going out to Quintana beach was a floating bridge- basically a barge. I drove a bobtail dump truck across that one time, and it seemed the end went down about a foot when I drove on. My dad said with the trailer dumps, the operator would come out and motion them to take it right down the middle.

RE: Overstressing a bridge

Of course it deflects. The depth of the stiffening girder/truss affects the amount of deflection.

RE: Overstressing a bridge

Wikipedia article notes bridge was pedestrian and cycles. Also noted bridge was temporarily closed this month because two overloaded buses went over it.

RE: Overstressing a bridge

The weight limit is 10 tons. A story said the bus was 35 tons.

RE: Overstressing a bridge

I think the bus is more likely 35,000 lbs- figuring 8 wheels at 80,000/18 lbs per wheel.

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