Sample Essay On The Tacoma Narrows Bridge Disaster

The 1940 Tacoma Narrows Bridge was the first United States suspension bridge constructed in the state of Washington. Specifically, its construction started in the 1930s, and opened to the public on July 1, 1940. It spanned the Puget Sound from Tacoma to Gil Harbour. On the areas where the bridge crossed, it was about a mile wide. During its construction and destruction, the bridge was the third longest suspension bridge worldwide, after the George Washington Bridge and Golden Gate Bridge. Specifically, it covered 5959 feet.
The bridge collapsed because of high winds as well as its high levels of flexibility. In the ensuing tragedy, only a dog was killed. According to Billah and Scanlan, there were high weeds blowing across the bridge, which caused the bridge to sway considerably (119). It collapsed at around 11 A.M. after the concrete dropped from the surface of the road. After a few minutes, a section of the bridge, covering about 600 feet, broke free. The bridge towers were constructed using strong structural carbon steel. However, the strong wind subjected it to violent movements, which eventually led to its collapse.
After the collapse, the state formed an immediate investigation Carmody Board, to establish the factors responsible for the tragedy. In March 1941, the Board released its finding. Essentially, the report indicated that the random action of the turbulent wind was the reason behind the collapse of the bridge. In explanation of the wind-induced motion of the suspension bridge, the report identified several main points. The first point indicated that its flexibility was the fundamental weakness, which made it vulnerable to the wind. It had a great flexibility, both in torsion and vertically. There were several factors, which contributed to its flexibility. It had a light deck, which was also too shallow, approximately 8 feet. In addition, its side spans were also too long as compared to the centre span length. Further, the deck has an extremely narrow width, as compared to its centre span length.
Another reason behind its collapses was the structure of the bridge. Billah and Scanlan indicated that the bridge caught and blocked the wind, instead of letting wind pass through (120). Additionally, during construction, engineers had not considered the effect of the aerodynamic forces, which was little understood. They did not test the designs suspension bridge using wind tunnel models.

Engineers’ Contribution to the Collapse

Engineers that constructed the bridge had a significant contribution to bridge construction. Engineer Leon Moisseiff designed the bridge, and it is the most flexible bridge ever constructed (Billah and Scanlan 121). The engineers believed that the bridge was completely safe, even though it exceeded the standard ratios of length, width and depth. However, after the collapse, it emerged that the designers and engineers failed to consider the effects of aerobic forces, which occurred in the area, during the periods of high winds. During construction, engineers and designers did not consider those forces.
The government of United States commenced the process of constructing a replacement bridge, which took more than two years of construction. It was launched on October 14, 1950. The replacement bridge is currently the fifth largest suspension bridge in the United States. It has 40 more feet in length than the original bridge. The construction of the replacement bridge took into account the lessons, which were learned from the collapse of the Tacoma Narrows Bridge.

Work Cited

Billah, K. Yusuf, and Robert H. Scanlan. "Resonance, Tacoma Narrows bridge failure, and
undergraduate physics textbooks." Am. J. Phys 59.2 (2010): 118-124.