>>663185 (last bread – I simply cannot keep up while meming!)
According to the article,
https:// www.npr.org/2017/08/01/540669701/10-years-after-bridge-collapse-america-is-still-crumbling
the cause for some of them is inadequate engineering. Engineering standards that were considered OK 50 years ago are no longer OK. We no longer design bridges in such a way that the failure of one critical component could cause the entire structure to fail. But 50 years ago, we did.
This particular Minneapolis bridge that failed in 2007 had 3 problems. It was "fracture critical" meaning one failure could collapse the entire structure (engineering design problem). It also was undergoing repair and tons of repair materials had been stockpiled on the structure, increasing the load (user/management engineering error). Third, after the failure, the steel gusset plates were found to be half the necessary thickness (construction error).
So whether any deficient steel was involved has not been stated by anyone who examined it. This is just from my reading; I'm not a structural engineer.
"The interstate highway bridge had been classified as structurally deficient, meaning that it was aging and in need of repair. In fact, some repair work was going on when it fell. And the bridge was also rated as fracture critical, meaning the failure of just one vital component could cause the whole bridge to collapse.
But in fact, neither of those classifications means a bridge is necessarily dangerous. And the National Transportation Safety Board determined that it was a design flaw, and not deferred maintenance, neglect, or other problems, that caused the 35W bridge to collapse. Gusset plates that hold the bridge's huge steel beams together were only half as thick as they should have been. The NTSB also found that nearly 300 tons of construction equipment and materials stockpiled on the bridge deck for the ongoing repair work contributed to the collapse by further stressing the crucial gusset plate that failed."