Since the YouTube video is of WTC 7 collapsing, perhaps the easiest way to answer your question would be to detail how IT collapsed:

"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. 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. 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.

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. 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. During the afternoon, fire was also seen on floors 6–10, 13–14, 19–22, and 29–30. In particular, the fires on floors 7 through 9 and 11 through 13 continued to burn out of control during the afternoon. 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. During the afternoon, firefighters also heard creaking sounds coming from the building. 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. At 5:20 p.m. EDT on September 11, 2001, 7 World Trade Center collapsed." -- http://en.wikipedia.org/wiki/Wtc7#Collapse

Helpful Answer?  (1)   (0)    Tip clarusvisum for this answer