If engineers were like pundits

"It's obviously George W. Bush's fault that the I-35 bridge collapsed. This is another Katrina by a thousand cuts. If the President had seen to our infrastructure the way he has seen to Iraq's--"

"Jane, you ignorant slut, this tragic bridge collapse is clearly the fault of the feather-bedding union highway workers, who were too stupid to stop taking up concrete when the bridge wobbled. I guess they were all Wobblies!"

"Dan, you bloated, blithering gasbag, this accident is an indictment of all Republicans. Tom Pawlenty, the Republican Governor, had recently vetoed a plan to raise funds for highway repair. He won't be--"

"Jane, you vicious lesbian hag, it's no wonder you're a socialist Democrat. You can't even get the Governor's name right. It's Tim, you research-free imbecile, not Tom."

"Dan, Tim, Tom, now he's ready to consider a gas tax incre--"

"Jane, you pathetic loser, don't change the subject. Any tax increase, you're for it. Money won't bring those people back."

Ladies and gentlemen, our national dialog.

That said, since I'm an amateur pundit, I have a theory about the bridge collapse, which I'm going to render here, despite a lack of obvious qualifications.

I think the bridge collapsed due to a perfect storm of three factors. Foremost, the pier in the Mississippi on the south end of the bridge had been severely scoured by the turbulent river water flowing out of the lock to the west.

Note: This CNN video was shot from the south end of the bridge, not the north end as the newsreader claims. The position of the Cedar Ave. Bridge (a/k/a 1oth Ave. Bridge) to the east makes that obvious. This position caused the security camera to miss the initial collapse on the south end.

With the pier essentially standing on water, the structural integrity of the bridge relied on the stiffness of the traffic deck to transfer load to other parts of the structure. Once the repaving team started to take concrete off the deck (factor two), the bridge started to wobble. The more they took off, the worse the wobble was.

In short order, the strain was too great, and the steelwork that held the span to the abutment on the south bank, no doubt weakened by road-salt-hastened corrosion (factor three, the least important), failed suddenly. The miracle is that it didn't fail with rush hour traffic on it and kill hundreds instead of tens.

What caused the rest of the bridge to fail? As the deck and truss to the south slewed east, the only remaining sound members of the south span were the tensile members - the steel truss - and they pulled the middle span of the bridge down.

I don't know why the span between the north pier and the north abutment failed. The north pier survived upright; maybe it suffered severe enough excursions south that its steelwork simply failed at the north abutment.

If this turns out to be right, it's still not a validation of Bill Kristol blathering on about subjects he obviously has no clue about.