One For The Road: The 1979 Rosemont Stadium Roof Collapse
By Samantha Abernethy in Arts & Entertainment on Aug 13, 2012 10:30PM
On this date in 1979, the roof of the Rosemont Horizon (which would later become Allstate Arena) collapsed and killing five workers and injuring 16. The wooden roof of the 20,000-seat arena was 90 percent complete when it suddenly collapsed. Shortly after the collapse, officials speculated about a low-flying aircraft causing the collapse, and Rosemont Mayor Donald E. Stephens told the AP that it was probably a gust of wind. However, an Occupational Safety and Health Administration investigation revealed, "The building was in such unstable condition that anything could have set off the collapse. You could have blown on it and knocked it down."
According to an engineering case studies project, shoddy planning and missing bolts are what caused the unfinished roof to collapse.
A post-collapse investigation carried by the Occupational Safety and Health Administration revealed that the cause of the collapse was the unstable condition of the wood roof frame. Over 53 percent of the required connection bolts were missing from the building's roof. Of the 944 girder bolts required for the connections already installed, only 444 were in place. Of these, 338 had no nuts, and some of the nuts in place were only finger-tight. OSHA also discovered that only 27 percent of the "compensating steel plates" were properly installed. Although the missing bolts were found the triggering cause, it was proved that inadequate bracing and the stockpiling of materials in the roof contributed to the collapse. Several other violations were attributed to the roof erector, who was severely fined by OSHA. The project's architect and other subcontractors were also fined for diverse irregularities. Even the independent engineering firm retained by the city to investigate the collapse was fined by OSHA for unnecessarily exposure of their employees to fall hazards during field inspection.In an interesting note, one year after the roof collapse, concrete stands under construction also collapsed at the Rosemont Horizon, dumping 34 tons of concrete to the ground. No fatalities or major injuries resulted from this accident.
The tragedy was featured on the History Channel's Engineering Disasters in 2004, if you'd like to learn more.