I'm also an engineer. Seems to me that dropping a bridge as completely as this would be a huge undertaking for Jonnie Jihadist. This wasn't terrorism.
It's pretty amazing how small a failure can be that causes this kind of catastrophe. The fact that there's been construction work in the area raises an immediate suspicion in my mind.
I'm supposed to be in Minneapolis on Saturday, too. I hope I have a chance to get a look at this scene while I'm there.
If this was terrorism, it would be visible. I’ve seen collapses where the load on the steel and concrete was calculated improperly and that’s what it looks like to me, the fact that there is major construction going on makes this all the more likely. Not to mention that all of the piles seem intact and that is where an explosive would have been placed.
“A steel member in a structure is typically designed to accommodate 40% more than its anticipated “dead” load and 70% more than its anticipated “live” load”
That may be what you require as an engineer, but as a steel detailer, I always design each end connections for 75% of the total uniform load. we always go further than what the engineer calls for. You are right this probably wasn’t terrorism, I just didn’t want people to think that traffic isn’t taken into consideration when designing a bridge. Or that crappy material would be used without many levels of checking. The engineers of this country and the AISC using ASD are the best in the world. I just don’t want people loosing faith in engineers.