Manage episode 291326649 series 2862916
Twelve people were hospitalized Saturday May 2, 2009 after the roof of the Dallas Cowboys' indoor practice facility in Frisco, Texas collapsed during a thunderstorm. The giant blue star atop the building lay crumpled on the ground. The storm knocked out power at team headquarters and splintered trees across the property. The roof was a large air- and tension-supported canopy with aluminum frames covering a regulation 100-yard football field. Approximately 70 players, coaches, staff and media were reported inside. Some of the injuries were serious, but none were considered life-threatening. Based on the national standards for determining loads and for designing structural steel buildings, the Commerce Department's National Institute of Standards and Technology researchers studying the Cowboys facility found that the May 2 wind load demands on the building's framework—a series of identical, rib-like steel frames supporting a tensioned fabric covering—were greater than the capacity of the frame to resist those loads. The researchers determined that, at the time of collapse, the wind was blowing predominantly from west to east, perpendicular to the long side of the building. Maximum wind speed gusts at the time of collapse were estimated to be in the range of 55 to 65 miles per hour—well below the design wind speed of 90 miles per hour in the national standard for wind loads. The NIST report recommended building owners, operators and designers inspect all fabric-covered, steel-frame structures, evaluating them to ensure they are designed to handle appropriate wind loads.
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