Images from the collapse of the Dallas Cowboys' practice facility at Valley Ranch on May 2, 2009.
The National Institute of Standards and Technology released its final report on the Cowboys indoor practice facility collapse.
The NIST reported the structure collapsed under wind loads significantly less than those required under applicable design standards. The group recommended that other fabric-covered frame structures be evaluated for safety.
The NIST came to its conclusions after recreating the covered facility in a two-dimensional computer model. The group analyzed the frame of the structure under various wind conditions. NIST said it worked with the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory to estimate the wind conditions at the time of collapse. The researchers determined that, at the time of collapse, the wind was blowing 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 as specified in the national standard for wind loads.
NIST and NOAA analyzed the available wind data and concluded that a microburst, a small, intense downdraft which results in a localized area of strong winds, was centered about one mile southwest of the structure at the time of collapse.
NIST said it is with public and private groups to implement changes to practice, standards, and building codes based on the findings from the study.