This bridge started to turn on itself under the effect of the wind

The Tacoma Narrows Bridge opened in July 1940. His apron has already shown movement during construction. Workers can observe vertical ripples: the structure is flexible, and this flexibility is visible even before the arrival of the first motorists.

On November 7, the behavior changed. The apron begins to twist: one edge rises while the other goes down. The movements become huge, and then part of the bridge collapses. The filmed images of the event made these oscillations famous.

The Washington Department of Transportation’s historical study describes an instability in the interaction between wind and structure. Air accompanies and amplifies torsion movements. It is not simply a bridge blown like an object on a table, nor is it a complete explanation summed up by the single word “resonance.”

Certain specific aspects remain discussed between specialists. The main phenomenon is documented: the movements of the structure and the flow of air have strengthened each other. The wind didn’t have to look like a hurricane to make this particular form of bridge difficult.