Most of the experts who examined her thought she was safe. In fact, most thought that her movements were little more than an annoyance and that those who lived or worked in her area should just ignore the undulations. Some felt that perhaps her shaking would just stop eventually as she settled in.
But, they were wrong. Eventually Galloping Gertie, as she was known, fell to her demise. It was during a windstorm. Windstorms had always affected her in this way, but this time it was different. Maybe the wind was stronger than usual on that day in 1940. The recorded wind speed of 42 miles per hour meant strong gusts. Gusts strong enough to bring Gertie crashing down.
Galloping Gertie had shaken until she fell. Who was this extraordinary mover and shaker? And why is Gertie an engineering
disaster to be remembered?
The Tacoma Narrows Bridge began to carry traffic over the Narrows of Puget Sound from Tacoma to Bremerton, Washington, on July 12, 1940. The bridge, designed by Leon Moisseiff, was the second longest bridge at the time of its construction. Only New Yorks George Washington Bridge was longer.
A cable-supported suspension bridge with two steel-plate girder bridges used as the approaches, the Tacoma Narrows Bridge was a sight to see. It was even more spectacular when she began to sway in the wind. In fact she shook and swayed so much that she earned the name Galloping Gertie.
Engineers attempted to steady Gertie with cables tied-down to 50-ton cement blocks. Stiffening girders were connected to the main cables. Nothing could keep Gerties movement in check.
Regardless, expert engineers pronounced the bridge safe and told the public that the movements were merely an annoyance. The undulations were merely a bad habit of Galloping Gertie.
In November 1940, just months after opening, Gertie proved the experts wrong as she tumbled in the 42 mile per hour winds. Fortunately, no one was fatally injured since there was adequate warning for those traveling on the bridge to move to safety.
While Gerties fall was a tragic mistake, Moisseiff was generally not faulted for poor design as this was the first structure of its kind and no standards for this sort of bridge had yet been developed.
The collapse of Galloping Gertie was captured on film, which was used as the basis of aerodynamic research for the new Tacoma Narrows Bridge that opened in 1950.
Actual
footage of Galloping Gertie including her fall
