A Textbook Engineering Failure: The Case of Galloping Gertie

Nov 7, 2017

This story originally aired on February 7, 2015.

In 1940, the Tacoma Narrows Bridge was a state-of-the-art engineering achievement, a dramatic suspension design spanning a strait of Puget Sound. Sure, it had a bit of a "bounce," but the engineers all assured the public that was normal. Only a handful of bridge workers seemed truly alarmed. 

Then one day, on November 7, a storm kicked up 40 mph winds, and the bridge began to contort. Soon its undulations took on a distinctive, twisting-ribbon pattern that got worse and worse as the winds pounded it. 

Because of several design flaws, the rhythm of the winds reinforced twisting. 

"You can sort of liken this to when a child is sitting on a swing and the loving parent is pushing the swing, if you get the pushes at the right time, then you don't have to push it very hard to make the oscillations bigger and bigger," said John Stanton, a professor of Civil and Environmental Engineering at the University of Washington. "As [the bridge] twists, the more the wind pushes it to twist even further. And eventually it just tore itself apart."

Galloping Gertie would become the poster child for failed engineering. It would be taught in classrooms across the world for decades to come -- including to a young undergraduate John Stanton, early in his studies in England. 

"I had no idea where Tacoma was, I didn't even know what continent it was on. But here was an amazing collapse," he said. 

Stanton joined Sound Effect to talk about Gertie's legacy, and a few troubling parallels to modern situations.