All models are wrong − a computational modeling expert explains how engineers make them useful

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Zachary del Rosario, Olin College of Engineering

(THE CONVERSATION) Nicknamed “Galloping Gertie” for its tendency to bend and undulate, the Tacoma Narrows Bridge had just opened to traffic on July 1, 1940. In a now infamous failure, in the face of moderate winds the morning of Nov. 7, 1940, the bridge started to repeatedly twist. After an hour of twisting, the bridge collapsed. One fatal engineering assumption led the bridge to shake itself apart.

At the time, many designers believed that wind could not cause bridges to move up and down. That may seem like an obvious fact now, but that incorrect assumption cost about US$65 million in today’s dollars and a dog’s life.

Small vertical movements allowed the bridge to twist. Near the end, the bridge twisted in ways the designers had never anticipated. This twisting stressed the bridge until the Tacoma Narrows Bridge collapsed.

By assuming no vertical movement from wind, the engineers didn’t study how parts of the bridge would flutter in the wind before they built the bridge. This oversight ultimately doomed the bridge.

This failure illustrates an idea that many engineering students learn during their coursework: All engineering calculations are based on models. Safe...