See #1564. There appears to be a great deal of twisting in that section.
Take a closer look at the picture!
Yikes, if you can not figure this out, get a beer. Will it tip over to one side if you bump it, or will if squash perfectly flat? Even a drunk knows that a beer will tip over on it's side!
Yes. Whatever side that was, it fought the failure first.
Yeah, look at 1585.
I can see that first northern approach sidespan pier or truss letting go, flexing the cantilever over the north mainspan pier. It cracks over the pier, the stresses snap the other end of the mainspan and it drops straight down.
The truss system remaining over the north pier, overloaded and losing integrity, fails and leans to the west, taking that piece of the sidespan deck with it.
My gut likes it.
Question, what happened to that sidespan pier/truss? It’s accessible from land, and probably on relatively dtable ground, compared to the riverside piers.