NIST: Fire caused the collapse of WTC 7

Issue 10 and Volume 161.

“Uncontrolled building fires—similar to fires experienced in other tall buildings—caused an extraordinary event, the collapse of World Trade Center 7 (WTC 7),” S. Shyam Sunder, lead investigator for the National Institute of Standards and Technology (NIST), reported at a news conference in August. This conclusion was reached, Sunder said, “by reconstructing the building, beam by beam, column by column, connection by connection into a computer model.” The investigation results are included in a draft of the report and recommendations available online at; NIST was accepting comments on the document up to September 15, 2008. The study took three years to complete. Among the findings contained in the report are the following: The collapse was not caused by explosives or fuel oil fires. Fires, which undermined floor beams and a critical structural column, led to the eventual collapse. The fires on Floors 7 through 9 and 11 through 13 were…

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