A couple of things I noticed:
- The bridge was more than 45 years old. It was designed and built when there were fewer cars on the road, and much less overall traffic. This isn't much of an excuse, but it could be a contributing factor.
- The construction taking place could have weakened existing faults.
- None of the media mentioned this so far, but I saw that a train was caught underneath one of the collapsed sections. It was traveling parallel to the river. Now, a full-loaded cargo train puts down quite a vibratory footprint as it travels.
That, combined with the construction, heavy traffic and the fairly harsh climate the bridge has been enduring were probably the last straw. The bridge finally threw up it's hands and said "F-you".
To those conspiracy theorists out there convinced that it was a terrorist event, here's a big dose of common sense:
- Note the 2nd bridge immediately north of the collapsed bridge. If it was a terror attack, they would have taken out both bridges. While terrorists are a-holes at the utmost level, they usually don't do half-assed work.
My heart goes out to those families who lost loved ones, and I wish the city of Minneapolis and it's people the the best during this time of disaster.