Tocama Narrows Bridge Engineering Disaster

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Jordan N. Gibson September 4, 2011 CEE 2804 Writing Assignment #1 The Galloping Gertie One of the most widely studied failures in the history of engineering, the Tacoma Narrows Bridge is a staple in every physics and engineering textbook across the board. From its humble beginnings in September 1938, it took only nineteen months to construct the third largest suspension span bridge in the world of its time. However, it took a mere four months to fall (Big Tacoma). Designed by one of the world’s foremost bridge engineers and top-ranked engineering consultants, Leon Moisseiff, how could such a spectacular structure fall? After numerous investigations were completed, it was discovered the collapse of the Tacoma Narrows Bridge was due to a combination of: a misconception of extreme flexibility of the structure, use of more economical but weaker materials, and the lack of realization of the strength of aerodynamic forces. The desire for the construction of a bridge between Tacoma and the Kitsap peninsula dates back to 1889 with a Northern Pacific Railway proposal for a trestle, but concentrated efforts began in the mid-1920s. Despite Moisseiff’s reputation, State and Toll Bridge Authority engineers were more than a little nervous about the behavior of the slender two-lane span measuring 2800 feet long and only 39 feet wide (Schlager). And they should have been. Early signs of failure began to rise when the bridge was charted as having small oscillations back and forth due to small wind gusts. Hence, the notorious bridge early on gained its nickname as the “Galloping Gertie” by people who experienced its wavy effects. Also, complaints of seasickness became very common. The twisting bridge deck caused the wind flow separation to increase. This formed a vortex, or swirling wind force, which further lifted and twisted the deck. The coiling caused metal fatigue, and the
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