Assessments of structural catastrophes—even if preliminary—can be excellent classroom resources.
By Henry Petroski
A number of tragic structural failures have occurred in the past couple of years. These incidents—euphemistically called accidents—have taken place in locations across the country and throughout the world.
The most highly visible failures were widely reported when they happened. And often within days, if not hours, of an incident, theories about what caused it abounded. There always seem to be engineers and scientists willing to give their opinion or describe their hypothesis about how and why a bridge or building collapsed.
Early blame is usually diffuse, ranging from design error to poor maintenance. This analysis is often, but not always, only partly correct. Still, even pending an official announcement of cause by investigators, preliminary assessments presented critically can be excellent resources for the classroom.
Among the most widely reported and discussed of recent structural failures was the 2018 catastrophic collapse of a cable-stayed bridge in Italy. The viaduct known as Ponte Morandi—named in honor of its engineer—stood for half a century, carrying a motorway high over a low-lying area of Genoa. The failure was attributed to unforgiving design details, corrosion, and poor maintenance.
In the same year, a pedestrian bridge was under construction across a busy thoroughfare in Miami, Florida. The first segment of this bridge, which was being built on an accelerated construction schedule, had been in place for only about five days when it suddenly collapsed, crushing vehicles beneath it at the time. The National Transportation Safety Board, which investigates such accidents, blamed the design itself, poor peer review of design calculations, and underestimation of the significance of cracks that were developing in the reinforced-concrete span.
Even more recently, the Hard Rock Hotel under construction in New Orleans suffered a partial collapse that damaged two tower cranes being used in erecting it. The weakened cranes were brought down quickly—a hurricane was about to hit the city—but the building structure itself was considered too unstable to be demolished without careful planning. Months after the accident, an official cause of the collapse was still to be determined.
Although these three structural failures did receive a lot of media attention when they took place, as time passed the events ceased to be news. This is typical of reaction to a disaster; it is in the news only until displaced by newer news. The professional trade press typically follows progress on the way to reaching a studied conclusion about the causes and implications of a failure, but those articles tend only to be read in engineering offices.
Tragic as such accidents are, they should always be described and discussed in engineering classrooms, with the most pedagogically useful of them becoming part of the canon of case studies. Root causes and lessons learned should be highlighted and incorporated into every student engineer’s educational experience. Failures are generally more instructive than success stories, but students may not even be aware of them.
My recent experience with college students is that only a small fraction of them keep up with the news. Whenever I have taught in a seminar setting, where discussion is not only encouraged but expected, I often have asked how many of the participants had heard of the latest widely reported failure. It may have happened as little as a day or a week earlier, but typically only one or two students out of 18 can even name the disaster, let alone discuss, meaningfully, early theories about it.
It behooves us to allow enough flexibility in a syllabus for an ad hoc description and discussion of a relevant failure that may have occurred just yesterday. In my experience, students welcome the connection with the real world and the opportunity to learn that catastrophes can often be traced to carelessness, error, or downright ignorance in applying theory to design. Students should know and remember examples of failure that make this clear.
Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University.
Image Courtesy of Catherine Petroski