Thunder Bay – Why Nipigon River Bridge Failed?

An interesting letter to the editor from a structural engineer who claims the bridge design is at fault and not the bolts…

If the issue is in the design and not just a flaw in the bolts , then fixing it just got more expensive.

Engineer explains why bridge failed

There is a design flaw in the Nipigon River Bridge. There are no tie down cables. I designed the first cable stayed post tensioned steel structure in the world in 1974 in suburban Chicago.

The Nipigon River Bridge has no tie downs. A 100 degree F temperature change causes the longest cable to contract up to 3 inches. That cable alone requires 600,000 pounds of force to extend it 3 inches. Thus the bridge curled up. – Chronicle Journal

read full article here

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