A horrific event. I saw some of the released video, what is the length of the collapse time, curious if that is included.
A theory floated last night by a weather guy was that an dam 200 yards upstream may have over time created enough of a disturbance of and removal of sediment and bedrock.
btw, I have not seen or reviewed a detailed map of that area so I am not sure where and how many and even if there are supports that could have been undermined in any way.
It also sounds like they had some lanes closed and slow moving bumper to bumper traffic that may have caused more load to be present , a ‘perfect storm’ of things if you will.
Obviously, there have been other failures and investigators will now need to compare those and this event to better determine what caused what we witnessed happen.
The bridge inspection by MnDOT would have noted any significant casson erosion. The safety factors on these bridges would allow you to park trucks stacked 3 high on top of each other in bumper to bumper before you’d be at the limits. It’s the simultaneous and complete failure of both trusses that bother me. This thing should have twisted if 1 side went. It didn’t.