BTW, the Kansas City Hyatt bridge was a suspended walkway inside the Hyatt Regency Hotel. Same reason for collapse as for this bridge in Minnesota. OVERLOADED.
That was a different issue in a sense. The original design wasn’t used and a “modified” design was used to support the two walkways. The modified design was far less structurally sound, though it should be noted the original design wasn’t sound itself - and it wouldn’t have supported that load.
No. Not quite. It was not overloaded. And the design was good. It was the shortcuts taken by the contractor that built the walkway that caused the collapse. The contractor built the walkway at variance from the design but got an engineer to sign off on the amended design. That engineer never bothered to re-calculate the stresses on the material, and that engineer lost his license because of it. The walkway in the Hyatt was designed to handle any load... which could not have been exceeded by people standing or dancing shoulder to shoulder on the bridge.
But it wasn't built to the design. And the as-built never really got any "engineering" at all. That's why it fell.
Actually, the KC bridge collapse happened was overloaded, but overloaded through bad design. It was an architecural/engineering error. The structural detail was changed during the project, and an inferior non-redundant detail was substituted. Too much load was transferred to the upper bridge beam. The effect was to double the load on one ‘nut’ that was literally holding up the platform. the beam split apart as people danced across the platform, causing vibrations. As the upper platform collapsed, it brought down the lower bridges.
http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse