A Cautionary Tale for Lightweight Structures
Interior of the Metrodome showing the collapsed roof. Photo by Craig Lassig/European Pressphoto Agency. Courtesy of The New York Times.
One of the primary means to mitigate architecture's environmental footprint is to reduce its physical mass. Buckminster Fuller's frequent query, "How much does your building weigh?" placed special emphasis on this criterion, and Fuller advocated the use of lightweight structures to contain maximum volume with minimal material. Architectural textiles have provided one means of accomplishing Fuller's goal, and the soft, inflatable, easily transportable structures that emerged in the latter half of the 20th century presented an image of a nimble, low impact future.
The use of architectural textiles in sports arenas has served as a particularly visible demonstration of their application, although the outcome has not always been positive. This weekend, for example, the Minneapolis-based Hubert R. Humphrey Metrodome fabric roof deflated under the weight of heavy snow. According to Metropolitan Sports Facilities Commission executive director Bill Lester, two of the triangular Teflon panels were damaged in the collapse. Although no one was injured as a result, the accident forced the relocation of Monday’s football game to Detroit.
According to a recent article in The New York Times, the Metrodome is covered in 10 acres of 1/16-inch thick Teflon-coated panels. The roof weighs approximately 580,000 pounds, which for 10 acres is surprisingly lightweight. To put things in context, the 17 inches of snow that fell on Minneapolis last Saturday exerted a weight of roughly 620,000 pounds on the roof (based on a typical snow weight of 15 pounds per cubic foot), more than its own weight. Luckily, the collapse did not create any lasting structural damage, and the roof will likely be repaired by midweek—a repeat experience of two prior collapses during the 1980s that were repaired in similar timeframes.
Thus, it is a testament to the resilience of textile-based structures that they can rebound quickly from such calamities—a fact that would likely make Fuller proud—although it would seem practical for lightweight structures to be designed such that they withstand such heavy, if infrequent, loading conditions (especially in Minnesota).