How the Legacy of Historic Engineering Failures Affects Us Today
I was told once that a mark of great engineering is that we take no notice of it. Plumbing, street lights, bridges, and other infrastructure exist all around us, and we rarely stop to appreciate their functionality. Instead, our attention is held by the devices and structures that fail us, whether it is in small or catastrophic ways. As an engineering student, I am often directed to look at footage of the Tacoma Narrows Bridge collapse in 1940. The bridge is seen swaying back and forth, twisting so severely that a driver is forced to leave his car behind and spectators gather to watch as the bridge breaks itself apart and falls into the water. In the nearly eighty years since, it has become one of the most recognizable suspension bridge failures of modern times. All around the world, people drive across bridges and trust they will make it to the other side. Accidents like the Tacoma Narrows Bridge are considered anomalies. As we continue to push the boundaries of engineering and choose to design and build more interesting bridges, buildings, and infrastructure, it is important to consider as many factors as possible that led to such a disaster occurring.
When evaluating footage of the Tacoma Narrows Bridge, the easy conclusion is that the wind put too much stress on the bridge. It was thought by many that the collapse was caused because the wind forced the bridge to vibrate at its resonant frequency. This is the same principle used when people ride swings. By matching the rate at which the rider kicks their legs with the resonant frequency of the swing, the swing moves higher and higher in both directions. In materials and structures, the theory was that vibrating at the resonant frequency causes maximum internal stress and can lead to failure. However, more recent theories have posited the wind was strong and continuous enough that it created vortexes going over the bridge. This caused it to vibrate from side to side, tilting at a larger angle with each tilt. Suspension bridges are designed to handle vertical vibrations, not the violent twisting seen in the Tacoma Narrows incident. At the time, wind was not considered a significant element in suspension bridge design. It was in part through this accident that engineers were forced to reconsider the principles behind stable and safe bridge design.
It is unfortunate to think that only disasters push people to reevaluate their designs and consider additional factors. While there were no human casualties in the Tacoma Narrows Bridge accident, other similar situations have not had such fortunate results. In the United States, hundreds of people have died in major bridge failure accidents in the last fifty years. Even as recently as 2007, a portion of the I-35 W Bridge in Minneapolis failed because its support plates were too thin, resulting in the deaths of thirteen people. While the majority of bridges do not fail, the ones that do are often caused by the designer not taking into account all the factors that cause stress and strain on the bridge. It makes sense that instances like these are put forward as examples before young engineering students. We are often asked to consider what we think happened, as well as other factors that should be considered in order to build safer bridges in the future. This seems like an effective way to encourage the critical thinking skills that inspire better engineers. However, we are still experiencing structural failures in bridges. The question of what we can do about it remains.
An important part of understanding technology in the modern era is recognizing that it is continually changing. Rather than learning every coding language that is currently used or focusing on the technology that exists now, people can be far better off understanding the basic principles of the current technology and learning how to adapt. It is inevitable that in a time of so much technological advancement, it will become increasingly important to do this. It is this principle that could be useful to remember for structural engineering practices. Anticipating problems before they become catastrophic failures is vital to the success of engineering projects. In the 1940s, engineers designed bridges and assumed the wind would never be strong enough to bring them down. Those types of assumptions have cost lives and money, as well as deprived people of necessary infrastructure. Not all problems can be anticipated, but when we fail to understand and publicize the errors that cause engineering disasters, these same mistakes can find their way into new designs. A situation of this nature occurred in 1978 when New York City’s new Citicorp Center was completed, but contained an important design failure that could cause the building to collapse if it faced significant winds. A college student who was learning how to consider some of these elements in structural design was the one who noticed and informed the designer so the building could be fixed before anyone could be hurt.
The Tacoma Narrows Bridge has become an example of what not to do as an engineer. While the designer is not a household name, the bridge is well-known for its failure. The average person remembers it as an accident they hope to never experience. Engineers remember it as an accident they hope to never cause. Either way, it is a reminder that society must continue to question how to create successful designs. People cannot afford to become complacent and assume plans have no significant room for improvement. Human innovation is what drives society forward. As technology advances, engineering should too. By doing so, engineers can continue to improve society with advanced infrastructure, gifting the rest of the world with the privilege to not take much notice of it.
"Citicorp Center Tower: how failure was averted." Engineers Journal, Engineers Ireland, 8 Dec. 2015, www.engineersjournal.ie/2015/12/08/citicorp-centre-tower-failure-averted/. Accessed 20 Jan. 2019.
Penn, Alexandrea. "The deadliest bridge collapses in the US in the last 50 years." Cable News Network, 15 Mar. 2018, www.cnn.com/2018/03/15/us/bridge-collapse-history-trnd/index.html. Accessed 20 Jan. 2019.
Siegel, Ethan, and Starts With A Bang. "Science Busts The Biggest Myth Ever About Why Bridges Collapse." Forbes, Forbes Media, 24 May 2017, www.forbes.com/sites/startswithabang/2017/05/24/science-busts-the-biggest-myth-ever-about-why-bridges-collapse/#19f96da51f4c. Accessed 20 Jan. 2019.
"Tacoma Narrows Bridge." Washington State Department of Transportation, www.wsdot.wa.gov/TNBhistory/Machine/machine3.htm. Accessed 20 Jan. 2019.