NIST releases final report on 9/11 WTC7 collapse

Posted by Rick C. Hodgin

Gaithersburg (MD) - Yesterday, the National Institute of Standards and Technology (NIST) released its final report on the September 11, 2001 collapse of World Trade Center building #7 (WTC7). The report states that a crucial column (number 79) failed due to uncontrolled fires burning on several floors which produced "an extraordinary event." Once column 79 failed, it "initiated a fire-induced progressive collapse that brought the building down."

NIST received comments from "the building community," and conducted an additional computer analysis of the structural failure of column 79 to see if it would still bring the entire building down at free fall speeds without damage caused by the collapse of WTC1 and WTC2. The investigation team concluded that "the column’s failure under any circumstance would have initiated the destructive sequence of events."

The report follows a two-year investigation into the collapse of WTC7 which, approximately 7 hours after the collapse of WTC1 and WTC2, came down at free fall speeds.

NIST reports that a three-year study of the collapse of WTC1 and WTC2 was conducted. It began in August, 2002 and concluded in October, 2005. As a result, more than 20 changes to the U.S. model building and fire codes have been adopted.

Read more about the report on the NIST press release.