I grew up in Seattle and got my BSME from UW. I remember a class where we watched the film of "Galloping Gertie" in its final death throws and then the road structure began to disintegrate.

Analysis was done at UW, which determined the probable cause of failure. One of the "aesthetically pleasing" aspects of the original bridge was the "thin" road support structure that consisted of fabricated solid beams beneath the road rather than an open truss structure such as the Golden Gate Bridge. It was an aerodynamic problem caused by this solid girder road support structure that caused the road structure to begin twisting - an oscillation would set up. It's analagous to the sound that's created when you blow across the top of a bottle since sound is just a pressure wave oscillation. The name "Galloping Gertie" was applied shortly after the bridge opened as movement was quite noticeable to users, and I think it failed only about two months after it opened in a relatively modest wind that was less than 40 knots - far below what the designers believed the bridge could easily stand.

The replacement bridge upped the total lane count from two to four and an open truss road support structure was used instead of the solid girder structure, which allowed the wind to pass through without creating significant displacement forces.

One other interesting anecdote that I recall. The State of Washington bought an insurance policy on the bridge, but the insurance broker, thinking that the chances of ever having a claim were remote, pocketed the premium and never established a policy with the underwriter. I don't recall if the state was able to collect anything, but I think the insurance broker went to prison!

Duke