6 Modern Engineering Miscalculations
Although engineering practices have evolved significantly to accommodate humanity’s need to build safe structures and develop critical infrastructural systems, the overall process isn’t perfect and errors do occur. In an effort to help prevent mistakes from occurring and to avoid miscalculations, civil engineers have gradually expanded their knowledge to develop practices and techniques that reduce human errors. By reviewing some of the most notable modern incidents of engineering miscalculations, civil engineers can glean valuable insight, effectively gaining an understanding of how to avoid repeating engineering mistakes of the past.
Soon after being completed in 1940, the Tacoma Narrows Bridge in Washington suffered a fatal collapse due to several design flaws. The most notable design flaw was the unusually slender frame of the bridge, measuring just 39 feet wide and only accommodating two lanes of traffic. Excessive side-to-side swaying and vertical flapping earned the Tacoma Bridge its nickname, Galloping Gertie. Though tourists and residents saw the bridge as a pseudo-roller-coaster ride, civil engineers and government officials recognized the danger and quickly made attempts to stabilize the volatile structure.
Unfortunately, all attempts to stabilize the bridge were made in vain, as on November 7, 1940, the Tacoma Bridge began to violently twist, shake, and undulate uncontrollably. Fortunately, nobody was atop the main section of the bridge when the center span broke off and fell into the Tacoma Narrows Strait below. While the bridge was designed to withstand winds of up to 120 mph, it collapsed in 42 mph winds. After investigation, civil engineers concluded that the collapse was caused by resonance, a phenomenon that hinged on the wind vibrating at the same frequency as the structure itself, causing a gradual increase in stress on the bridge until it eventually gave out under the pressure. Today, as a result of this event, engineers have implemented mandates that demand wind tunnel testing of bridge designs and the incorporation of complex structural frequencies when designing new bridges in order to prevent the recurrence of this dangerous phenomenon.
The Hubert H. Humphrey Metrodome in Minneapolis, Minnesota first opened in 1982 as a venue to serve Minnesota’s major league baseball and football teams. The Metrodome is notorious for suffering catastrophic failures, as the domed inflatable roof of the structure has collapsed five times, most recently in December 2010. The first three failures, occurring annual between 1981 and 1983, were attributed to the accumulation of snow and debris. While the fourth event in 1986 was considered a casualty of strong winds, the most recent collapse was, again, caused by a massive accumulation of snow.
The 2010 collapse was the result of a severe winter storm dumping upwards of seventeen inches of snow in the region. This record snowfall overtook the facility’s snow removal crew. Though an emergency team led by a civil engineer attempted to use steam heated water and heat redirection to overcome the snowfall, this crew was unsuccessful in their efforts. Eventually, once the roof threatened to collapse, all workers were evacuated. Prior to the 2010 collapse, the two-layer roofing system had been inspected by its installer, Birdair, and though they had recommended taking immediate action for repairs, management of the facility decided to hold off on efforts to replace or repair the structure. In the end, tearing caused by massive amounts of snow and ice, coupled with the roof’s old age, spurred global failure by deflation and inversion of the 28-year-old dome. Air-supported roof structures are now being reconsidered, as they require professionally coordinated maintenance, like expensive heating, insulation, and constant monitoring by civil engineers to prevent sudden failures.
The Oroville Dam is seated in the foothills of the Sierra Nevada in the city of Oroville, Nevada. The dam was constructed in 1968 to prevent flooding and other water-related incidents, while also providing the state with water for personal and recreational use. In February 2017, engineers recognized that the Oroville Dam’s main spillway was damaged and water had begun to flow into the auxiliary spillway, which had over time suffered from erosion damage.
As a result of the damaged spillway, officials evacuated 200,000 residents, noting that if the auxiliary spillway broke apart, a 30-foot wall of water could rush from the lake and inundate the surrounding communities. Dam operators and engineers were able to lower water levels successfully, but only time will tell what impact future precipitation will have on this vital infrastructure. Civil engineers will continually monitor the Oroville Dam for potential risk factors that may impact human life in the future. By routinely examining the overall safety, stability, and integrity of the dam’s foundational structures, civil engineers can help to ensure that the Oroville Dam continues to remain stable.
St. Francis Dam
The collapse of the St. Francis Dam in Los Angeles was a devastating event that resulted in nearly 400 deaths—the second highest loss of life caused by a natural disaster in California’s history. The incident occurred on March 12, 1928, only two years after the dam’s completion and was attributed to poor engineering decisions and unchecked human errors that occurred during the planning phases of the project’s construction.
Several of the specific instances of poor judgment made during the planning and building process has been documented, namely the disregard for site-specific investigations when preparing plans for the engineering of the dam. After construction had already begun, plans were made to raise the height of the dam to accommodate additional reservoir space, but no changes were made to the base of the dam. This and several other oversights, including a lack of review of the construction plans by an independent engineering party, resulted in the dam failing. From this event, civil engineers have learned that due diligence in the form of cross-referencing and verifying the reliability of construction plans with third-party sources is important for maximizing the preservation of human life.
Minneapolis I-35W Bridge
The I-35W highway bridge, which ran over the Mississippi River in Minneapolis, Minnesota, collapsed on August 1, 2007. This incident resulted in 111 vehicles being dropped into the water, 145 people being injured and 13 lives lost. The bridge, which was opened to traffic in 1967, had been extended and renovated several times prior to its collapse. Immediately after this event, investigations began on the cause of the bridge failure in order to gain information that could help prevent similar events in the future. The investigations found that high volumes of construction materials located on the bridge the day of the collapse played a significant role in the failure of the bridge.
The addition of the construction materials was a perfect storm for failure, because several hundred thousand pounds of building materials were staged on the bridge to accommodate plans for repaving certain sections of the structure. This additional weight, combined with the weight of usual traffic, triggered bending instability in several gusset plates, which were later determined to only be half as thick as the design specifications required. Had the civil engineers working on renovating, auditing, and repairing the bridge taken notice of this detail, such tragic loss of life may have been prevented. Civil engineers are now trained to take into account all of a structure’s attributes—especially existing design flaws—when planning an extensive renovation or redesign. Engineers are now also trained to account for how added reconstruction stresses, such as added weight from construction vehicles, may impact the original design.
Hyatt Hotel Walkway
On July 17, 1981, the Hyatt Regency Hotel in Kansas City, Missouri suffered from a structural failure, as the second and fourth floor walkways collapsed from use during an event. Rods were connected to the ceiling supporting these walkways; however, under the weight of people standing and dancing on the walkways, these rods failed. This event is regarded as the most catastrophic structural failure in United States history, with 114 recorded deaths and approximately 200 injuries.
Investigations of the event showed that this devastating collapse could have been prevented if the involved parties had taken more proactive preventative measures. For instance, prior to the hotel opening for business, the walkways’ roof connections failed. An engineering firm reached out to offer on-site representation, which would have allowed them to step in to acknowledge and reconcile design flaws, but the principle of the hotel refused due to the anticipated additional costs. The owner of the Hyatt Hotel property cut corners in a failed attempt to save money, resulting in many expensive lawsuits against his personal company, bankruptcy and the loss of engineering licenses among several of the engineering firms involved, and worst of all, a massive number of casualties. In response to this engineering miscalculation, civil engineers immediately reformed the design review phase, and engineering designs are now often thoroughly reviewed by a third party for potentially concerning risk factors.
From the above examples of engineering miscalculations, civil engineering students and professionals can learn a variety of lessons regarding professional integrity, due diligence, and accountability. Civil engineering coursework is designed to inform students of overall best engineering practices, helping to prevent such engineering incidents from occurring. Using knowledge gained from advanced civil engineering coursework, practicing civil engineers can help societies expand their infrastructure with minimal danger to human life.
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Tearing into the Metrodome: Are Other Air-Pressurized Stadiums Unsafe and Outmoded?, Scientific American
Tacoma Bridge collapses, History.com
Case Study: St. Francis Dam (California, 1928), Association of State Dam Safety Officials
Bridge Collapse in Minneapolis Kills at Least 7, The New York Times
Hyatt Regency Walkway Collapse, Engineering.com