Emergency inspection to be done on several in MN with the same design.
I have watched the video a number of times.
I observe that the end of the bridge which mates up to land (or a low-mounted support near land) is the first to fall.
That actual junction is not visible in the frame – it is off camera to the right.
But you can see from the displacement of the bridge that the breakage occurs first at or near the point of joining to the land. That to me seems ridiculous.
The main truss is unaffected throughout most of the span, but then shears at the point of main support, about half way across the river. This is due tothe fact that the span has, at that point, already dropped straight down due to loss of support on the land end. The subsequent breakages all make sense, but the first one doesn’t.
MnDOT says this thing was OK in 2006. Minnesota has a major culture of proper maintenance because of the winter snows and deicing.
The very fast, immediate failure of the bridge at the point mating to land is, to me suspicious. The loss of the support on the land mating side seems to beinstantaneous across the entire support. This didn’t lose 1 girder on one side or a domino effect of girders. They seemed to all go at once.
Also supporting that observation is a complete lack of torque. This bridge falls straight down. There is no twisting motion. Both sides of that bridge were released simultaneously. After the first breach, then sections
across the bridge go one after another, which follows rationally.
My read is a very fast and simultaneous breaking of the support at the land mating point.
I find it, then, insulting to the intelligence that we are instantly told by the police chief and Washinton “it wasn’t terrorism, it wasn’t terrorism, it wasn’t terrorism.”