I meant to post on this a while ago and forgot all about it. Perhaps that's because, from what I can tell, it never came up again. The PiPRess did a story earlier in the month suggesting - surprise, surprise, the stress cracks that critics excoriated MnDOT for may not have had anything to do with the I-35W bridge collapse:
...a closer look at the record throws into question the idea MnDOT could have prevented the collapse by reinforcing the Minneapolis bridge, as an outside consultant recommended. The record also casts doubt on the theory that fatigue cracks made the bridge fall.
-- The cracks were repaired in the 1990s. And they were never found in the main I-35W river span, which appeared to fall first on video of the collapsing bridge captured by a U.S. Army Corps of Engineers surveillance camera.
-- The cracks were on the approach spans, which were not "fracture critical." That designation signals a risk of total collapse if one key part of the bridge fails. The fracture critical area of the bridge was in the main span.
-- A proposal to strengthen the steel beams in the bridge's main span by adding steel plates dealt with a speculative problem - potential cracks. The reinforcement also would not have guaranteed against a total collapse.
As well, the story notes that stress cracks usually give out in cold, not hot, weather. It puts me in mind of this story, shortly after the collapse.
Time will tell what brought the bridge down, but contrary to unhinged lefty opinion, it's looking less and less like it had anything to do with a lack of taxes, or Iraq.