[quote]Petedacook wrote:
What is the cause of the collapse of WTC VII according to the “Official Story” and what is the source of that information?
[/quote]
As the North Tower collapsed on September 11, 2001, debris hit 7 World Trade Center, causing heavy damage to the south face of the building.[3] The bottom portion of the building’s south face was heavily damaged by debris, including damage to the southwest corner from the 8th to 18th floors, a large vertical gash on the center-bottom extending at least ten floors, and other damage as high as the 18th floor.[3] The building was equipped with a sprinkler system, but had many single-point vulnerabilities for failure: the sprinkler system required manual initiation of the electrical fire pumps, rather than being a fully automatic system; the floor-level controls had a single connection to the sprinkler water riser; and the sprinkler system required some power for the fire pump to deliver water. Also, water pressure was low, with little or no water to feed sprinklers.[27][28]
After the North Tower collapsed, some firefighters entered 7 World Trade Center to search the building. They attempted to extinguish small pockets of fire, but low water pressure hindered their efforts.[29] A massive fire burned into the afternoon on the 11th and 12th floors of 7 World Trade Center, the flames visible on the east side of the building.[30][31] During the afternoon, fire was also seen on floors 6â??10, 13â??14, 19â??22, and 29â??30.[3] In particular, the fires on floors 7 through 9 and 11 through 13 continued to burn out of control during the afternoon.[32] At approximately 2:00 p.m., firefighters noticed a bulge in the southwest corner of 7 World Trade Center between the 10th and 13th floors, a sign that the building was unstable and might collapse.[33] During the afternoon, firefighters also heard creaking sounds coming from the building.[34] Around 3:30 pm FDNY Chief Daniel Nigro decided to halt rescue operations, surface removal, and searches along the surface of the debris near 7 World Trade Center and evacuate the area due to concerns for the safety of personnel.[33][35] At 5:20 p.m. EDT on September 11, 2001, 7 World Trade Center collapsed. There were no casualties associated with the collapse.
In May 2002, the Federal Emergency Management Agency (FEMA) issued a report on the collapse based on a preliminary investigation conducted jointly with the Structural Engineering Institute of the American Society of Civil Engineers under leadership of Dr. W. Gene Corley, P.E. FEMA made preliminary findings that the collapse was not primarily caused by actual impact damage from the collapse of 1 WTC and 2 WTC but by fires on multiple stories ignited by debris from the other two towers that continued unabated due to lack of water for sprinklers or manual firefighting. According to FEMA, structural elements were exposed to high temperatures for a sufficient period of time to reduce their strength to the point of collapse[6]; nevertheless, it has since been determined that the fires burned out in 20 minutes at any given location as they moved from point to point.[15]
Source found on Wikipedia’s Notes section: 7 World Trade Center - Wikipedia