Galloping Gertie: The Bridge That Taught Engineering

The first Tacoma Narrows Bridge opened to traffic on July first, nineteen forty. It was two thousand eight hundred feet of main suspended span across the narrows of Puget Sound, a significant engineering achievement and, as it turned out, a significant engineering failure.

Construction workers had noticed almost immediately that the bridge moved. Not imperceptibly, the way all long-span bridges move, but visibly, rhythmically, in moderate wind. They called it Galloping Gertie. Drivers reported feeling seasick crossing it. Engineers who studied the oscillations noted that the bridge's solid plate girder design, chosen for aesthetics and economy, was presenting the wind with a solid surface rather than an open truss, creating lift forces the structure was not designed to handle.

On the morning of November seventh, nineteen forty, wind entered the narrows at forty-two miles per hour, which was not exceptional for that location. The bridge began twisting. A journalist for the Tacoma News Tribune named Leonard Coatsworth had been crossing when the oscillations began to worsen. He abandoned his car and crawled to safety on the heaving deck. His daughter's cocker spaniel, Tubby, was still in the car. Coatsworth tried to retrieve the dog. Tubby bit a professor who also attempted the rescue. The dog would not move. Coatsworth had to leave without him.

Tubby was the only fatality when the bridge collapsed into the Narrows that morning. The car was eventually appraised at eight hundred fourteen dollars, Tubby included.

The footage of Galloping Gertie's collapse, shot by a camera shop owner who had driven out to film the oscillations, is now among the most-watched engineering films in history. It is shown in physics classrooms around the world as the definitive example of aeroelastic resonance, the phenomenon the bridge's designers had not calculated for. The current bridge, opened in nineteen fifty, has an open truss design.