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Title: 9/11 demolition theory challenged
Source:
BBC
URL Source: http://news.bbc.co.uk/2/hi/science/nature/6987965.stm
Published: Sep 11, 2007
Author: staff
Post Date: 2010-07-17 17:31:29 by buckeroo
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Keywords: None
Views: 39287
Comments: 1209
An analysis of the World Trade Center collapse has challenged a conspiracy theory surrounding the 9/11 attacks. The study by a Cambridge University engineer demonstrates that once the collapse of the twin towers began, it was destined to be rapid and total. One of many conspiracy theories proposes that the buildings came down in a manner consistent with a "controlled demolition". The study suggests a different explanation for how the towers fell. Over 2,800 people were killed in the devastating attacks on New York. After reviewing television footage of the Trade Center's destruction, engineers had proposed the idea of "progressive collapse" to explain the way the twin towers disintegrated on 11 September 2001. This mode of structural failure describes the way the building fell straight down rather than toppling, with each successive floor crushing the one beneath (an effect called "pancaking"). Resistance to collapse Dr Keith Seffen set out to test mathematically whether this chain reaction really could explain what happened in Lower Manhattan six years ago. The findings are to be published in the Journal of Engineering Mechanics. Previous studies have tended to focus on the initial stages of collapse, showing that there was an initial, localised failure around the aircraft impact zones, and that this probably led to the progressive collapse of both structures. Man stands amid rubble of the World Trade Center, AFP/Getty Once the collapse began, it was destined to be "rapid and total" In other words, the damaged parts of the tower were bound to fall down, but it was not clear why the undamaged building should have offered little resistance to these falling parts. "The initiation part has been quantified by many people; but no one had put numbers on the progressive collapse," Dr Seffen told the BBC News website. Dr Seffen was able to calculate the "residual capacity" of the undamaged building: that is, simply speaking, the ability of the undamaged structure to resist or comply with collapse. His calculations suggest the residual capacity of the north and south towers was limited, and that once the collapse was set in motion, it would take only nine seconds for the building to go down. This is just a little longer than a free-falling coin, dropped from the top of either tower, would take to reach the ground. 'Fair assumption' The University of Cambridge engineer said his results therefore suggested progressive collapse was "a fair assumption in terms of how the building fell". "One thing that confounded engineers was how falling parts of the structure ploughed through undamaged building beneath and brought the towers down so quickly," said Dr Seffen. The south tower of the World Trade Center collapses, AP Conspiracy theorists see evidence of a "controlled detonation" He added that his calculations showed this was a "very ordinary thing to happen" and that no other intervention, such as explosive charges laid inside the building, was needed to explain the behaviour of the buildings. The controlled detonation idea, espoused on several internet websites, asserts that the manner of collapse is consistent with synchronised rows of explosives going off inside the World Trade Center. This would have generated a demolition wave that explained the speed, uniformity and similarity between the collapses of both towers. Conspiracy theorists assert that these explosive "squibs" can actually be seen going off in photos and video footage of the collapse. These appear as ejections of gas and debris from the sides of the building, well below the descending rubble. Other observers say this could be explained by debris falling down lift shafts and impacting on lower floors during the collapse. Dr Seffen's research could help inform future building design.
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#237. To: buckeroo (#0)
This is just a little longer than a free-falling coin, dropped from the top of either tower, would take to reach the ground. Actually a free fall from the 110th floor would have taken 9.22 seconds. Wow, the towers fell FASTER than free falling objects, like being sucked into a huge vacuum cleaner. Amazing.
Show me your calculation and/or source material.
Oh man, are you REALLY that stupid? Besides it being stated in virtually every report that exists in terms of free fall comparisons, here's the basic physics, which you apparently never learned in school. You can look up the formula, it's t = SQRT(2d/g) t = time, d = distance, g = acceleration due to gravity (32.2 feet per second/second) The roof heights of the WTC towers were 1368 ft for WTC1, 1362 feet for WTC2. Acceleration due to gravity is (32.17 feet per second)/second For WTC1; t = SQRT(2*1368/32.17) = 9.222 seconds For WTC2; t = SQRT(2*1362/32.17) = 9.202 seconds So there you go buck, try looking things up yourself next time before you make a fool of yourself.
Why do you think that your height measurement for the "top" of each of the WTC towers is correct? The towers were hit on the 96th and 81st floors, this means that "free fall" time values were 8.61 and 7.91 seconds respectively because this is the location of initial forces (de plane! de plane!) that buckled the upper floors. So, you are incorrect by throwing your silly brick off the 110th floor... for a publick demonstration of your astounding assumptions to thwart otherwise serious study and investigation into and about a tragic issue. This notion of "free fall" has always been used by the TWOOFERS and it is an incorrect assumption for the top of either of the building for the calculation; it is utter nonsense.
The towers were hit on the 96th and 81st floors, this means that "free fall" time values were 8.61 and 7.91 seconds respectively because this is the location of initial forces (de plane! de plane!) that buckled the upper floors. Oh, so you're saying the TOPS OF THE BUILDING JUST VANISHED INTO NOTHING? Man you people are really something. (Well you would be PARTIALLY correct in that they DID turn into dust). The TOPS of the building ALSO HAD TO FALL, and it is THAT we are talking about, for the top of the building to come to rest, not skipping the part of the collapse that had to occur PRIOR to the BOTTOM structure collapsing.
Can you explain that particular pulverizing phenomena?
Maybe your fellow shyster can explain it to you. Most rational people understand that EXPLOSIVES are more than likely to blame, or some other form of weapon. The pulverization is obvious if you watch the collapse videos, where there would NOT have been enough solid mass to "pancake" the floors, since there WERE no floors left of the upper structure.
But no known acoustic energy of tremendous quantities occurred until the final floors collapsed. Here is a diagram that shows it: If we had EXPLOSIONS ... those would have been recorded throughout and/or prior actual the collapse.
So even though there were TRILLIONS of JOULES of energy being absorbed into the ground during the collapse, there was no seismic record of that till the last few floors hit, ok then, so it would have been impossible to detect explosives.
In fact here is a pdf file about the seismic records from columbia university: www.ldeo.columbia.edu/LCS...0911_WTC/WTC_LDEO_KIM.pdf .... look it over ..... where are the explosions?
There are no replies to Comment # 278. End Trace Mode for Comment # 278.
Top • Page Up • Full Thread • Page Down • Bottom/LatestHis calculations suggest the residual capacity of the north and south towers was limited, and that once the collapse was set in motion, it would take only nine seconds for the building to go down.
#246. To: FormerLurker (#237)
Actually a free fall from the 110th floor would have taken 9.22 seconds.
#247. To: buckeroo (#246)
Show me your calculation and/or source material.
#249. To: FormerLurker, AGAviator (#247)
#255. To: buckeroo (#249)
Why do you think that your height measurement for the "top" of each of the WTC towers is correct?
#258. To: FormerLurker (#255)
(Well you would be PARTIALLY correct in that they DID turn into dust).
#261. To: buckeroo (#258)
Can you explain that particular pulverizing phenomena?
#268. To: FormerLurker (#261)
Most rational people understand that EXPLOSIVES are more than likely to blame, or some other form of weapon.
#271. To: buckeroo (#268)
But no known acoustic energy of tremendous quantities occurred until the final floors collapsed. Here is a diagram that shows it:
#278. To: FormerLurker (#271)
Replies to Comment # 278.