Engineering Disasters: Applying Lessons Learned from Failure
The infamous crash of the Tacoma Narrows Bridge in 1940 and the world's largest oil spill in the Gulf of Mexico in 2010 are just 2 examples of engineering disasters that have occurred throughout history. Design failures involved in such catastrophes have changed our approach to civil, structural, and mechanical engineering projects. In the wake of grim tragedy, development of safer methods occurs in the hope of preventing history from repeating.
Students are likely familiar with the trial-and-error method of solving algebra problems, but they might not think that the same method applies to solving engineering problems. When the Tacoma Narrows Bridge—the world's third-longest suspension bridge at the time—failed, no one thought of not trying to build a suspension bridge again. Following the Deepwater Horizon oil spill, deepwater drilling continued after a short suspension. (The event also caused tightening of drilling regulations.) In the bridge collapse and the oil spill, engineers sought to discover what went wrong and how to correct it.
As students attempt to build their own structures or inventions, they will begin to see that their first design rarely works. It is the process of design, testing, failure, and redesign that leads to innovation. When we consider the large number of engineering endeavors undertaken, it is incredible how few failures actually occur. This is because tedious planning and testing behind the scenes prevent most potential failures.
Building models is an important aspect of predicting and avoiding problems that might occur with full-scale applications. Models are generally smaller, more quickly built, less-expensive versions of the final project. Modern engineering methods rely on computational models to predict the stress on and resilience of various materials and designs. Specialized software can generate 3-D computer models that engineers can manipulate to test simulations without ever building a tangible object. Some elements of these methods were the result of analyzing past engineering failures.
Tacoma Narrows Bridge collapse
The Tacoma Narrows Bridge twisting shortly before its collapse in 1940.
In July 1940 the suspension bridge over the Tacoma Narrows opened. Even during the bridge's construction, something was obviously wrong. The undulating movement of the structure's deck was so strong during windy conditions that the span was nicknamed “Galloping Gertie.” Only 4 months after opening, the bridge gave way, crashing into Puget Sound.
This engineering disaster has become 1 of the most studied examples of structural design failure. Physics, mathematics, and engineering professionals and students alike applied their knowledge of forces and aerodynamics to evaluate what went wrong. Forced resonance from the continuous wind often receives blame for the failure, but further studies point to a phenomenon called aeroelastic flutter. Due to the bridge's solid sides and narrow length, the wind could violently vibrate the structure. The vibration, acting in a kind of positive feedback for itself, escalated to dangerous levels. The lessons from this failure have influenced the design of the great suspension bridges built since. Modern suspension decks are wider and of greater mass to reduce vibrations, and these decks also have an open design so that wind can pass through.
Deepwater Horizon oil spill
In February 2010, the Deepwater Horizon oil rig was drilling an exploratory well 41 miles off the southeast coast of Louisiana. Numerous safety mechanisms were in place to keep the flow of oil under control. But just 2 months later, on April 20, as the rig's crew prepared to seal and leave the well, a number of things went wrong and mistakes were made.
The Deepwater Horizon oil-drilling rig burning in the Gulf of Mexico in 2010.
A blowout preventer—a giant piece of safety equipment designed to shut the entire system down and cut off the flow of gas and oil between the well and the Gulf in case of an emergency—was in place on the seafloor. The standard procedure for abandoning a well was to fill it with special cement that sealed gases and oil in the earth. Questions remain about the composition of the cement used as the sealant for the Deepwater Horizon well and whether or not that cement was capable of withstanding the pressure deep inside the well.
Rushing through the process of sealing the well, the crew failed to conduct certain safety checks and ignored signs of problems. A giant mass of mud, methane, and water surged up from the well and erupted at the surface. The change in pressure from the bottom of the well to the water’s surface caused the crystalline methane to become gaseous. Sparks on the rig ignited the methane, causing a series of explosions that killed 11 crew members.
An effort to shut off the flow of oil and gas via the blowout preventer failed because the explosions had rendered the device ineffective. There were additional attempts, using various backup methods, to stop the flow of oil from the ruptured well. Over the course of the next 6 months an estimated 200 million gallons of oil poured into the Gulf of Mexico, and it didn't stop until the well was finally sealed in September 2010. The spill caused extensive damage to marine wildlife and the Gulf’s fishing and tourism industries.
Many engineering and regulatory issues came to light following the Deepwater Horizon disaster. The composition of the cement sealant, effectiveness of the blowout preventers, and contingency methods for recovery all required engineering fixes. In the coming years we will no doubt hear continued debate about the human and environmental safety issues connected to deepwater drilling and the industry changes and equipment improvements intended to alleviate related concerns.
Discussing engineering disasters with your students might ignite their interest in design, innovation, and problem solving. If nothing else, it will highlight human perseverance and the tendency of engineers to develop better, safer structures in the wake of failure. When students understand how many trials it takes professionals to create a working model, they may be more willing to keep trying after their first brush with failure.