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Uploaded on Jan 28, 2009
The National Institute of Standards and Technology (NIST) conducted an extensive three-year scientific and technical investigation of the Sept. 11, 2001, collapse of the 47-story World Trade Center building 7 (WTC 7) in New York City. This video describes the results of this study, which concluded that fires on multiple floors in WTC 7--which were uncontrolled but otherwise similar to fires experienced in other tall buildings--caused an extraordinary event. Heating of floor beams and girders caused a critical support column to fail, initiating a fire-induced progressive collapse that brought the building down.