Footage from November 7, 1940 showing the collapse of the Tacoma Narrows Bridge and demonstrating the power of the phenomenon of resonance.

Note: On the day of the collapse, the Tacoma Narrows bridge experienced resonance from vortex shedding. Apart from its usual vertical deflections, the bridge experienced a torsional motion and started twisting before 45 minutes of its collapse. Normally in bridges, the wind would pass through the trusses. But the replacement of trusses with narrow H-shaped girders led to flow separation and hence the formation of a vortex. Another possible debate is that the collapse might be caused due to aeroelastic flutter. It is an unstable, self-excited, structural oscillation at a definite frequency and the energy is derived from the motion of the structure itself.

When resonance frequency matches wat happens (bridge frequency =air frequency)=Crash – YouTube