Tacoma Narrows Aeroelastic Flutter

Aeroelastic Flutter

The Tacoma Narrows Bridge failed due to aeroelastic flutter — a self-excited torsional oscillation, NOT simple resonance.

Wind Speed: 20 mph Structural Damping: 5% Deck Width/Depth: 30

(Tacoma Narrows: ratio ~72, modern bridges: ~30)

Stable

Above the critical flutter speed (~35 mph for Tacoma Narrows), aerodynamic forces couple with torsion to create negative damping — oscillations grow without bound until structural failure.