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In a video, it appears that WTC 7 is descending in free fall, something that would not occur in the structural collapse that you describe. How can you ignore basic laws of physics?In the draft WTC 7 report (released Aug. 21, 2008; available at http://wtc.nist.gov/media/NIST_NCSTAR_1A_for_public_comment.pdf [Links inactive - To make links active and clickable, login or click here to register]), NIST stated that the north face of the building descended 18 stories (the portion of the collapse visible in the video) in 5.4 seconds, based on video analysis of the building collapse. This time period is 40 percent longer than the 3.9 seconds this process would have taken if the north face of the building had descended solely under free fall conditions. During the public comment period on the draft report, NIST was asked to confirm this time difference and define the reasons for it in greater detail.To further clarify the descent of the north face, NIST recorded the downward displacement of a point near the center of the roofline from first movement until the north face was no longer visible in the video. Numerical analyses were conducted to calculate the velocity and acceleration of the roofline point from the time-dependent displacement data. The instant at which vertical motion of the roofline first occurred was determined by tracking the numerical value of the brightness of a pixel (a single element in the video image) at the roofline. This pixel became brighter as the roofline began to descend because the color of the pixel started to change from that of the building façade to the lighter color of the sky.The approach taken by NIST is summarized in Section 3.6 of the final summary report, NCSTAR 1A (released Nov. 20, 2008; available at http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201A.pdf [Links inactive - To make links active and clickable, login or click here to register]) and detailed in Section 12.5.3 of NIST NCSTAR 1-9 (available at http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201-9%20Vol%202.pdf [Links inactive - To make links active and clickable, login or click here to register]).The analyses of the video (both the estimation of the instant the roofline began to descend and the calculated velocity and acceleration of a point on the roofline) revealed three distinct stages characterizing the 5.4 seconds of collapse: * Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall). * Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall) * Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravityThis analysis showed that the 40 percent longer descent time—compared to the 3.9 second free fall time—was due primarily to Stage 1, which corresponded to the buckling of the exterior columns in the lower stories of the north face. During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below. This is consistent with the structural analysis model which showed the exterior columns buckling and losing their capacity to support the loads from the structure above. In Stage 3, the acceleration decreased as the upper portion of the north face encountered increased resistance from the collapsed structure and the debris pile below.
I have to ask What JP, Hero Member means that "conspiracy theories refuse to accept this"?
Ok...I watched all 3 videos.
As far as I could tell, one big issue was the start and end time in the analysis. David Chandler seemed to only look at the video until the center of the building was obscured, while NIST apparently continued until none of the building was visible.
See discussion around minute 2:22 on second video. A large portion of the building to the right is still clearly visible after David Chandler stopped his measuring.
There may have been a period near the start of the collapse where the acceleration was high, approaching 1G. However, the rest of the collapse appeared to fall at constant velocity (nearly zero acceleration).
Sorry, I have no demolition experience. I do find it interesting that the roof comes down nearly evenly, parallel to the ground, except for the center section that comes crashing down first (and may even completely disappear from view).
Many of these skyscrapers depend on a central columnar support (perhaps around the so-called penthouse). If that central column buckled, then it might take the rest of the building down pretty much stepwise as apparently happened.
As far as what happened to the concrete and steel...These are huge, massive buildings. I'm showing:200,000 tons of steel425,000 cubic yards of concrete.12,000 miles of power lines.Anybody volunteer to store that in their backyard?
At 1¢ to 4¢ per pound, for scrap steel... that is $20 to $80 per ton. That gives somewhere between $4 Million and $16 Million in scrap steel. I suppose just a drop in the bucket when compared to the entire value of the buildings and cleanup, but should the government seize it?
How about a chunk of land designated to holding the evidence one of the greatest crimes this nation has every incurred?