In 1940, the newly built Tacoma Narrows Bridge in Washington State began to vibrate due to winds. The driving frequency matched one of the bridge's natural "modes", and the amplitude of oscillation got larger and larger. Within hours, the entire bridge had collapsed. It was a spectacular failure. It's not that the wind was so strong, and it's not that the wind was "pulsing", the resonance effect was subtler - it was the matching of the bridge's natural vibration frequency to the driving frequency (resonance!) which in this case arose from a steady wind that generated periodic vortex shedding off the bridge that ultimately took it down.
I welcome your comments on the class and this website.
Send them to steven.pollock at colorado.edu