09-19-2006, 05:15 AM
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#584 (permalink)
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Devils Cabana Boy
Location: Central Coast CA
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Quote:
Originally Posted by fastom
Remarkable similarity, no? And the buildings in Vegas were not hit with airplanes at all. You don't s'pose somebody blowed 'em up?
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free fall speeds:
Quote:
Originally Posted by http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm
6. How could the WTC towers collapse in only 11 seconds (WTC 1) and 9 seconds (WTC 2)—speeds that approximate that of a ball dropped from similar height in a vacuum (with no air resistance)?
NIST estimated the elapsed times for the first exterior panels to strike the ground after the collapse initiated in each of the towers to be approximately 11 seconds for WTC 1 and approximately 9 seconds for WTC 2. These elapsed times were based on: (1) precise timing of the initiation of collapse from video evidence, and (2) ground motion (seismic) signals recorded at Palisades, N.Y., that also were precisely time-calibrated for wave transmission times from lower Manhattan (see NCSTAR 1-5A).
As documented in Section 6.14.4 of NIST NCSTAR 1, these collapse times show that:
“… the structure below the level of collapse initiation offered minimal resistance to the falling building mass at and above the impact zone. The potential energy released by the downward movement of the large building mass far exceeded the capacity of the intact structure below to absorb that energy through energy of deformation.
Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos. As the stories below sequentially failed, the falling mass increased, further increasing the demand on the floors below, which were unable to arrest the moving mass.”
In other words, the momentum (which equals mass times velocity) of the 12 to 28 stories (WTC 1 and WTC 2, respectively) falling on the supporting structure below (which was designed to support only the static weight of the floors above and not any dynamic effects due to the downward momentum) so greatly exceeded the strength capacity of the structure below that it (the structure below) was unable to stop or even to slow the falling mass. The downward momentum felt by each successive lower floor was even larger due to the increasing mass.
From video evidence, significant portions of the cores of both buildings (roughly 60 stories of WTC 1 and 40 stories of WTC 2) are known to have stood 15 to 25 seconds after collapse initiation before they, too, began to collapse. Neither the duration of the seismic records nor video evidence (due to obstruction of view caused by debris clouds) are reliable indicators of the total time it took for each building to collapse completely.
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Quote:
Originally Posted by fastom
I don't think it was 1500 F at all. I'm not sure how NIST figures 1832 degrees how did they sample that?
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Quote:
Originally Posted by http://wtc.nist.gov/pubs/NISTNCSTAR1-5FDraft.pdf page 39
…Six experiments were performed within the compartment, of which five were simulated because Tests 1 and 2 were replicate tests. Figures 4–6 and 4–7 show pictures of an actual test and a corresponding simulation. Both the heat release rate and the compartment temperatures were compared. Figure 4–8 displays comparison plots of measured and predicted heat release rates. Figure 4–9 displays the upper layer temperature for Test 1 at four locations (clockwise from upper left: near window, between workstations, behind workstations, rear wall). The measured and predicted temperatures for all the tests were similar to those shown in Fig. 4–9. Peak temperatures near the compartment opening were about 1,000 °C, decreasing to 800 °C at the very back of the compartment. The trend was captured in the simulations. The decrease in temperature was important because in the simulations of the WTC fires, the only basis of comparison was the visual observations of fires around the exterior of the buildings. It was important to demonstrate that the model not only predicted accurately the temperature near the windows, but also the decrease in temperature as a function of distance from the windows. The temperature predictions for the other tests were similar and are included in NIST NCSTAR 1-5E….
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They know the temperatures reached 1000C because they ran test to simulate the conditions, both physically and through computer simulations, both came up with a high bound of 1000C. instead of saying ‘I don’t know so they musty be lying about it’ try doing some real reassearch findng how they knew it
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