Civil Engineering Fails

 

CIVIL ENGINEERING FAILS

Construction failures has been a serious issue all around the globe. Errors in structural design and poor construction practices are the major causes leading to the disaster in civil engineering world. Here are some of the examples of devastating construction failures in history and the destruction they caused.

1. Tacoma Narrows Bridge, Washington:

Source: https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge

The basic design principle of any structure is to ensure that the structure is capable of bearing the loads that it may be subjected to. In addition to the human or vehicle loads and the structures’ self weight, the loads also include the rain, snow, flood and even the wind loads.

On 1^st July, 1940, the Tacoma Narrows Bridge was opened to traffic between Tacoma, Washington and the Kitsap Peninsula. Financing being the major problem, the bridge was constructed using two narrow plate girders to stiffen the deck rather than the originally proposed trusses.

Source: https://www.quotemaster.org/suspension+bridge

Even under moderate winds, the bridge was too flexible during the construction because of which the construction workers gave it a name “Galloping Gertie”. On 7^th November, 1940, only after 4 months after it opened, the bridge collapsed.

 

So, what do you think the reason behind it? Yes, it is the resonance that caused the bridge to oscillate so violently. Resonance phenomenon occurs when the frequency of the driving periodic force meets the natural frequency of vibration which results in maximizing the amplitude of vibration. The bridge experienced the vertical oscillation because of the resonance due to “vortex shedding” which says that the vortices are created at back of a body when fluid like air or water flows past the bluff or blunt body.

Aerodynamics of the bridge has a major role in the collapse. The formation of low pressure zones or vortices caused the twisting motion of the bridge resulting in aeroelastic flutter (unstable oscillation due to airstream).

The resulting stress was too much to handle for the suspension cables and the bridge eventually failed. Thankfully, there were no human casualties in the collapse.

2. The Quebec Bridge, Canada:

Source: https://historicbridges.org/

River-way across the Saint Lawrence River was the main route of trade for Quebec. Ferries or ships were used to cross the river during summer but the crossings and the trade would have to be cut off during winter because of frozen path. Knowing the importance of the crossings, local political leaders and businessmen came together to form a Quebec Bridge Committee.

Several experts analyzed the site and probable loadings, they came to the conclusion that the bridge should be the cantilever one, not the suspension.

 

The bridge could connect Quebec city to the city of Levis. The cantilever bridge concepts were new in those days and there were no one much experienced for the construction over 300 ft. There were only four to five cantilever bridges before the Quebec Bridge was undertaken. By that time, Quebec bridge was the longest and the largest cantilever structure to be constructed having the span of about 1800 ft. Canadian Government selected a famous American Civil Engineer Mr. Theodore Cooper as an in charge of the project. He concluded that the design proposed by the Phoenix Bridge Company as the best and the cheapest cantilever superstructure plan. The chief design engineer was Peter L. Szlapka.

The construction work began in 1900 and continued as per plan till 1906 when Cooper realized that the design calculations made by Peter consist of severe mistakes. By that time the construction had progressed a lot. He preferred not to stop the work. Cooper left to New York stating his bad health and never visited the site. Edward Hoare and Norman McLure were now supervising the work.

As the actual load was much heavier than that of the design made by Peter, the chord of south cantilever arm started to bend. McLure repeatedly informed Cooper about it but he told them not to stop. McLaure himself went to New York to let Cooper know about the actual condition of the bridge. After brief discussion, Cooper wired a message saying “Add no more load to the bridge until after due consideration of facts”. He informed to Phoenixville Office rather than directly relaying it to the site because he thought the instant actions would be taken if the message went to the site through Phoenixville. McLure then went to the Phoenixville for in-person discussion. On his way, he assured to wire the information to the site but in his rush to the Phoenixville, he neglected to send the information. In absence of chief engineer, the message from Cooper was ignored at Phoenixville office. When the chief engineer returned, he arranged a meeting with McLure and had a discussion about the circumstances. Meanwhile at the site, the bridge collapsed with a thunderous roar. Out of 86 workers present on the bridge, only 11 were able to survive.

With more strong and accurate design, Canadian Government tried to rebuild the bridge. For the final stage of the work, the last central span was to lift and attached to the projected cantilever arm on both sides.

On 11^th September, 1916, the middle span collapsed again causing the death of 13 workers. In August 1919, after the loss of 88 workers and cost of about 25 million dollars, the construction was finally completed which is still the world’s longest cantilever bridge till date.