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Response to Name removed (Reply #15)

Tue Mar 3, 2015, 05:54 PM

16. WTC 7 Damage pic



NIST WTC7 FAQ

8. Why did WTC 7 collapse, while no other known building in history has collapsed due to fires alone?

The collapse of WTC 7 is the first known instance of a tall building brought down primarily by uncontrolled fires.

21. Did debris from the collapse of WTC 1 cause damage to WTC 7's structure in a way that contributed to the building's collapse?

The debris from WTC 1 caused structural damage to the southwest region of WTC 7—severing seven exterior columns—but this structural damage did not initiate the collapse. The fires initiated by the debris, rather than the structural damage that resulted from the impacts, initiated the building's collapse after the fires grew and spread to the northeast region after several hours.

The debris impact caused no damage to the spray-applied fire-resistive material that was applied to the steel columns, girders, and beams except in the immediate vicinity of the severed columns. The debris impact damage did play a secondary role in the last stages of the collapse sequence, where the exterior façade buckled at the lower floors where the impact damage was located. A separate analysis showed that even without the structural damage due to debris impact, WTC 7 would have collapsed in fires similar to those that occurred on Sept. 11, 2001. None of the large pieces of debris from WTC 2 hit WTC 7 because of the large distance between the two buildings.

22. Would WTC 7 have collapsed even if there had been no structural damage induced by the collapse of WTC 1?

Yes. Even without the structural damage, WTC 7 would have collapsed from the fires that the debris initiated. The growth and spread of the lower-floor fires due to the loss of water supply to the sprinklers from the city mains was enough to initiate the collapse of the entire building due to buckling of a critical column in the northeast region of the building.

http://www.nist.gov/el/disasterstudies/wtc/faqs_wtc7.cfm

WTC 7 Fast and Furious


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