What amazes me, though, is that even under this tremendous swaying, the bridge still held out for over an hour! That's some strong sh*t there.
I'm always amazed by that footage. I studied aerodynamics in college and love the physics involved with the collapse. I especially find it interesting how the bridge motion was primarily twisting, not side-to-site or up-and-down as can been seen by watching the centerline of the road at about 2:10 in the video. It's also good to remember that bridge designs changed considerably after the collapse to prevent it from happening again.
Yes, they have to do something to change the "note" of the bridge, like holding down a guitar string.