[jim_trent]

Nothing much on the video other than it probably wasn’t C-4 or terrorists.

My WAG (and right now everyone who says what made it happen is guessing) is that there was a fatigue crack in a non-redundant tension member. It may have been covered up by a facia, bird crap, or soemthing else. Or, it may have been where it was difficult for the “snooper truck” to reach and the inspectors just eyeballed it from a distance. Or maybe someone just falsified the records, saying they looked but didn’t. In any case, the crack finally got large enough that it could not hold the load with rush-hour traffic and it broke. When it broke, the entire rest of the bridge came down.

[jeffers]

In this image, looking southwest from the adjacent Cedar Bridge, considering what's on top of what, what appears to be in good shape, (SW cantilever kingpost, green lines, blue arrows)), what appears to be crumpled, (SE cantilever kingpost, red line, red arrows), and what doesn't seem to be visible at all (lateral bracing and diagonals between the cantilevers, red lines), it's hard to ignore this as a critical area in the collapse progression.