Bridge collapses in Minnesota

[iron81]

BS, Civil Engineering

There have been a few people in this thread who know more about bridges than me, but my best guess is that the bridge deck was balanced on the piers. Once one span dropped, there would be enormous torque forces on the other span that would normally be balanced out by the first span almost like a counterweight. There are no fasteners strong enough to resist that kind of torque. The remaining span would simply slide off the pier.

Another guess is that when the center spans began to fall, they remained attached to the outer spans, pulling those sections apart. I'm not in Civil Engineering now, but hey, its the internet where everyone's an expert.