This is pretty awful.

Fox story about Minneapolis bridge collapse.
James Lileks links to a safety engineer’s reaction to the bridge’s last structural evaluation.
I saw where someone said “and Minnesota’s not even an earthquake zone”, but even if it isn’t (and I disagree that it isn’t; lots of folks would say the same thing about Indiana, forgetting that we’re sitting in the New Madrid fault zone), this just looks like mechanical failure after 30 40 years of twisting in the wind and rebounding and vibrating due to heavy traffic. My guess is that the NTSB report will find that the bridge was simply underbuilt (or built to a “minimum standard” that wasn’t sufficient). Otherwise I can’t imagine why you’d have the kind of fracturing in the steel that was described in May 2006. I mean, bridges (and any other large structure) can’t be built rigid; they have to account for thermal expansion and contraction, vibration, wind pressure, and any number of other factors that require them to be “elastic”. Yet the report the engineer is reacting to talks about failures that appear to be due to twisting (“out of plane”).
I also saw someone talking about corrosion due to pigeon urea. Come on, folks. They paint those bridges on a regular basis, and they’re built out of corrosion-resistant steel to begin with. WATER is corrosive (think rust). The only way this bridge could have been in a more corrosive environment would be if it had been built in salt water. (LATER THOUGHT: Well, yeah, road salt. But road salt doesn’t cause out-of-plane twisting. And again — that’s why they sandblast and paint bridges on a regular basis.)
I think this is going to end up being like the pedestrian bridge at the hotel in KC years ago — either somebody skimped on materials, or the design of the bridge was just deficient.
And I know I’ll never get Sally on the Skybridge again.
A BIT MORE: Lileks today also points to an article on the Popular Mechanics website regarding the collapse. Money grafs:

The fact is that Americans have been squandering the infrastructure legacy bequeathed to us by earlier generations. Like the spoiled offspring of well-off parents, we behave as though we have no idea what is required to sustain the quality of our daily lives. Our electricity comes to us via a decades-old system of power generators, transformers and transmission lines—a system that has utility executives holding their collective breath on every hot day in July and August. We once had a transportation system that was the envy of the world. Now we are better known for our congested highways, second-rate ports, third-rate passenger trains and a primitive air traffic control system. Many of the great public works projects of the 20th century—dams and canal locks, bridges and tunnels, aquifers and aqueducts, and even the Eisenhower interstate highway system—are at or beyond their designed life span.
In the end, investigators may find that there are unique and extraordinary reasons why the I-35W bridge failed. But the graphic images of buckled pavement, stranded vehicles, twisted girders and heroic rescuers are a reminder that infrastructure cannot be taken for granted. The blind eye that taxpayers and our elected officials have been turning to the imperative of maintaining and upgrading the critical foundations that underpin our lives is irrational and reckless.