[youtube]http://www.youtube.com/watch?v=j-zczJXSxnw[/youtube]
This must be the most famous resonance of all time.
If you’ve never seen the 1940 collapse of the Tacoma Narrows suspension bridge, check out one of the many videos of the event, such as this one.
The torsional waves are similar to the wave demo we have in class, though of course about 100 times larger.
A related phenomenon afflicted the Millenium Bridge in London, though the driving force was footsteps rather than wind and it didn’t lead to catastrophic failure.