Tacoma Narrows Bridge, 1940

 by Victoria de Bruijn

On the 1st July 1940, the Tacoma Narrows Bridge opened to traffic, however, it dramatically collapsed into Puget Sound that same year - earning the nickname “Galloping Gertie”. Throughout its short existence, the suspension bridge, which spanned the Tacoma Narrows strait in Washington, was the world’s third-longest suspension bridge - following the Golden Gate Bridge and the George Washington Bridge. The bridge’s collapse has been regularly described as spectacular and a phenomenon, gaining the attraction of engineers and mathematicians. 

The only victim of the collapse was a three-legged dog. Woefully, a black Cocker Spaniel was left in the backseat of a lone car, abandoned on the galloping bridge, which could not be saved. Leonard Coatsworth was attempting to drive across the four-month-old Tacoma Narrows Bridge when he was forced to vacate his car 500 metres from the Toll Plaza due to the extreme wind storm. Three people attempted to save the dog: Coatsworth; a friend of his, Howard Clifford; and finally Professor F.B. Farquharson, who had arrived to observe the bridge’s motion. Each potential hero was met with aggressive-presenting fear from the dog, thus, they were unable to save him without bearing physical torment.

Despite several damping measures, the bridge began to move up and down in windy conditions - even after being opened to the public. The main span finally collapsed in 42 mph winds on the morning of 7th November as the deck oscillated in an alternating twisting motion that gradually increased in amplitude. Due to the steady wind speed, Professor Farquharson deduced that the resonant frequency of the bridge was 0.2 Hz. Such a phenomenon, now titled resonance, occurs when the driving frequency - for example the wind - matches the resonant frequency of the bridge causing a spike in the amplitude of oscillations and the bridge to suddenly collapse. 

The portions of the bridge still standing following the collapse, including the towers and cables, were dismantled and sold as scrap metal and the portion in the water now serves as an artificial reef. In 1950, a new Tacoma Narrows Bridge opened in the same location using the original bridge’s tower pedestals and cable anchorage. Resonance continues to serve as a dangerous phenomenon for engineers today, however, more effective damping measures have been fabricated to reduce the probability of such a collapse. Thus, the new Tacoma Narrows bridge still stands today.