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Old 11-05-2008, 04:36 PM  
hershie
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Join Date: Jun 2002
Posts: 4,642
It's very obvious what caused WTC 7 to collapse. What did the NIST studies miss? Why ignore the evidence and just post a stupid youtube video instead.

From http://en.wikipedia.org/wiki/7_World_Trade_Center

In its progress report, NIST released a video and still-photo analysis of 7 World Trade Center before its collapse that appears to indicate a greater degree of structural damage from falling debris than originally assumed by FEMA. Specifically, NIST's interim report on 7 World Trade Center displays photographs of the southwest façade of the building that show it to have significant damage. The report also highlights a 10-story gash in the center of the south façade, toward the bottom, extending approximately a quarter of the way into the interior.[41][3] A unique aspect of the design of 7 World Trade Center was that each outer structural column was responsible for supporting 2,000 sq ft (186 m²) of floor space, suggesting that the simultaneous removal of a number of columns severely compromised the structure's integrity.[42] Consistent with this theory, news footage shows cracking and bowing of the building's east wall immediately before the collapse, which began at the penthouse floors.[3] In video of the collapse, taken from the north by CBS News and other news media, the first visible sign of collapse is movement in the east penthouse 8.2 seconds before the north wall began to collapse, which took at least another 7 seconds.[3][43]

The working hypothesis, released in the June 2004 progress report and reiterated in a June 2007 status update, was that an initial failure in a critical column occurred below the 13th floor, caused by damage from fire and/or debris from the collapse of the two main towers. The collapse progressed vertically up to the east mechanical penthouse. The interior structure was unable to handle the redistributed load, resulting in horizontal progression of the failure across lower floors, particularly the 5th to 7th floors. This resulted in "a disproportionate collapse of the entire structure."[40][44][3]

On August 21, 2008, NIST released its draft report on the causes of the collapse of 7 World Trade Center, beginning a period for public comments.[33] In its investigation, NIST utilized ANSYS to model events leading up to collapse initiation and LS-DYNA models to simulate the global response to the initiating events.[45] NIST determined that diesel fuel did not play an important role, nor did the structural damage from the collapse of the twin towers. But the lack of water to fight the fire was an important factor. The fires burned out of control during the afternoon, including on floor 13, where a critical interior column buckled. With the buckling of that column, adjacent columns also failed along with the floor structure above. This triggered a vertical progression of floor failures to the roof. The collapse then progressed east-to-west across the structure, and ultimately the entire structure collapsed. The fires, fueled by office contents, along with the lack of water, were the key reasons for the collapse.[46]

Conspiracy theorists believe the building collapses on September 11, including that of building seven, were the result of controlled demolition.[54][55][56][57] The draft NIST report rejected this hypothesis, as the window breakages and blast sound that would have occurred if explosives were used were not observed.[58]
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