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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: 19034
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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Begin Trace Mode for Comment # 521.
#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.
Hahahahhaa. More back pedaling after they themselves use 9.22 seconds as evidenced on Rosie's video clip. Where she's obviously parroting something she doesn't understand the least from a CT website.
Rosie is obviously brighter than you. You don't judge collapse time for only PART of the building collapsing, you INCLUDE the ENTIRE building from the very top. Do they give you stupid pills on your job?
You're the people bantering around the "9.22 seconds," "physical impossibility" phrases. You've had over 8 years and still can't come up with coherent, supportable, verifiable versions of events. Take another few years to get your stories straight. It's not like anybody will be holding their breaths.
Yep, the building SHOULD NOT HAVE collapsed as if it were falling through a vacuum, yet buck's expert "calculated" precisely that. Do you and he subscribe to "Junk Science Monthly"? Or do you just make this shit up as you go?
There is a very good reason why real world controlled demolition uses so much time, energy, and materials to create conditions getting as close to free fall speeds as possible. And the consequence of this reason is, if the collapse does not approach free fall speeds, it wasn't done by professional controlled demolition experts. The reason is, it is known with complete certainty that the force of gravity, if unobstructed by other forces, will pull the building straight down into its own footprint. Where it can be neatly disposed of without damage to anything else not intended to be destroyed. When the structure is not sufficiently prepared by getting rid of any and all remaining obstacles in the way of straight down vertical collapse, there are additional uncertainties introduced of timing, and rerouting gravitational forces in lines other than straight up and down. So professional demolitions people take extra time to make sure the fall will be as close to vertical free fall speeds as possible to avoid introducing other variables which may cause unpredicable unmanageable results. If a building doesn't fall at close to free fall speeds, its fall has not been set up by controlled demolition. Fifeeen seconds vs. nine seconds for a collapse is not even close to free fall speeds. The controlled demolition theory is debunked by actual and observed free fall speeds indicating lack of thorough setup for a building collapse many times larger than the largest recorded CD.
Wrong. All the demolition has to do is START the collapse, and with strategically placed charges and computer aided timing, the collapse can take however long they want it to in terms of structural collapse below the initial point of failure. Thing is, it collapsed WAY too fast for gravity to have done it alone, where a falling body meeting resistance slows down, and the resistance may eventually give way, but it takes some finite amount of time for that to happen. You're saying it took 6 seconds to smash and break EVERY iota of resistance, since the 9 seconds of falling through a vacuum doesn't correlate with the time it took to overcome the resistance.
But a demolition did not start the collapses. The jet crashes did.
Er, no buckie. The buildings did NOT start to fall down when they were hit. They did NOT start to fall till the precise time they collapsed.
So there was no debris scattered around immediately after the impacts? Not much time... it was amazing they stood for so long ... but it took time for the central structure to lose stress capability that caused the later crush down phase.
Not amazing at all, what's amazing is that they fell at all, never mind disintegrate into dust while coming down close to free fall speeds.
ROTFL .... no building is designed to withstand that kind of impact.
So what IS your excuse for WT7? Also the architect for those buildings claims they were indeed made to endure the impact of a 747. Also, this architect calls BS on much of the story......he has far more experience in this field than you do Buck.
Your story is FALSE or fabricated. The twins were designed for a 707 as in a FOG with a velocity well below 550mi/hr. (For you, that means much less inertial force as what occurred on 9/11 by the relative impacts caused by terrorist crashes)
You prove, once again, that you don't know wtf you are talking about. Statements by Engineers Engineers who participated in the design of the World Trade Center have stated, since the attack, that the Towers were designed to withstand jetliner collisions. For example, Leslie Robertson, who is featured on many documentaries about the attack, said he "designed it for a (Boeing) 707 to hit it." 2 Statements and documents predating the attack indicate that engineers considered the effects of not only of jetliner impacts, but also of ensuing fires. John Skilling John Skilling was the head structural engineer for the World Trade Center. In a 1993 interview, Skilling stated that the Towers were designed to withstand the impact and fires resulting from the collision of a large jetliner such as Boeing 707 or Douglas DC-8. Our analysis indicated the biggest problem would be the fact that all the fuel (from the airplane) would dump into the building. There would be a horrendous fire. A lot of people would be killed, ... The building structure would still be there. 3 A white paper released on February 3, 1964 states that the Towers could have withstood impacts of jetliners traveling 600 mph -- a speed greater than the impact speed of either jetliner used on 9/11/01.
The twins were designed for a 707 as in a FOG with a velocity well below 550mi/hr. (For you, that means much less inertial force as what occurred on 9/11 by the relative impacts caused by terrorist crashes) You prove, once again, that you don't know wtf you are talking about. No, Tw00fster, you don't know WTF you're talking about. Federal airspace rules prohibit any commercial aircraft from going over 250 KIAS below 10,000 altitude or in "Class B airspace" which surrounds jet airports. New York City is completely covered by both restrictions. There would be no reason to design a building able to withstand a crash whose speed presumably never would be allowed by Air Traffic Control in the first place. Furthermore, structural engineer calculations aren't built in mockups and then tested to make sure the calculations are correct. Last but not least, there is no record of a design specifying a 500 mph impact. This is hearsay unsupported by any files. If you have a file supporting 500 mph impact of a 707/767 the produce it. You lie, you lose.
Well then, you've lost long ago if that's true...
Loser, here is a partial list of deficiencies you cannot answer with any satisfaction. As time goes on the list will get bigger. Just as a partial list, you've been provided explicit proofs of the following phenomena and many others.
Glad you posted that so that some of the folks who think Hani Hanjour actually did what they claimed he did will know that he could NOT have done it. They get quiet when you mention that he allegedly took control somewhere in the skies over Ohio and then flew it back to the Pentagon like a stunt pilot. But at the time the plane was hijacked, even if the weather had been perfect and not a cloud in the sky, he would not have had any idea where he was over the landscape. It all looks pretty much the same from heights greater than the top of Mt. Everest. And it is certain that a man who couldn't fly a Cessna could not fly what they claimed hit the Pentagon.
The most difficult parts of pilot tests are takoffs and landings. Hanjour didn't have to do either when he took over an aircraft already airborne and intended to be crashed, not landed.
The most difficult parts of pilot tests are takoffs and landings. Take-offs and landings in a Cessna are relatively easy, with the take-off being such that just about ANYONE could do it. Flying is the relatively easy part. Hanjour couldn't do any of the above even in a Cessna, never mind a heavy multi-engine airliner with all of the complex systems that need to be set correctly. We are supposed to believe however that he brought the plane down from 35,000 feet to treetop level at 400+ mph, then performed a manuever not any professional pilot could pulloff, and that is to descend to 20 feet off the ground at 530 mph (which is basically performing a landing), defying the laws of aerodynamics (in terms of ground effect), flying straight and level directly into the Pentagon wall. Yeah right. Hanjour didn't have to do either when he took over an aircraft already airborne and intended to be crashed, not landed. Besides LANDING the aircraft short of having his wheels down, AT 530 MPH (which the aircraft basically CAN'T DO), he navigated the plane from Ohio without any navigational aids in terms of ground references, so we must assume he was familiar with IFR (instrument flight rules) procedures using sophisticated flight systems and instruments, where he couldn't even fly a Cessna VFR, (visual flight rules).
Ohio? Why are you bringing up FLT77 on this thread? Don't you remember your "cabin door" thread of FLT77? American Airlines Flight 77 is the plane that is commonly believed to have crashed into the Pentagon. It was a Boeing 757-223 on a scheduled flight from Dulles to Los Angeles, with 58 passengers, four flight attendants, and two pilots.
Your pal AGovShill posted about it, bitch at him. The autopilot was engaged and disengaged multiple times Are you aware of the fact you have to PROGRAM the flight computer for the autopilot to know where to go? Are you aware of the fact YOU HAVE TO KNOW WHERE YOU ARE FIRST in order to do that? Are you aware of the fact it's practically IMPOSSIBLE to land a 757 at 530 mph, yet this "pilot" who couldn't fly AT ALL according to his instructors was able to pull it off ON THE PENTAGON LAWN, without so much as disturbing a blade of grass, then impacting the Pentagon wall straight on?
Hey Half Truther circlejerk. Hanjour got a commercial pilot certificate in 1999. He didn't follow up on it because he didn't care. Not because he was incapable. He spent all his time just prior to 911 with the simulator. That's because that was all he cared about, because he damn well knew his mission would not involve takeoffs and landings.
Provide the following information;
1.Where did he obtain this license? 2.What was the name of his instructor, and the name of the flight school? 3.Where and when did he get his private license? 4.What was the name of that instructor, and that flight school? Go to hell and do your own research, Half Truther. Try to prove I'm lying and once again you'll get clouted. All this documentation is freely available online. I already posted links where you could have followed through and found everything out yourself. But no, you'd much prefer exchanging circlejerk gaybanter with your fellow cultists, than finding out anything real. So you've been putting your priorities where you think they belong- Circlejerk Fairyland instead of the evidence probviding subject matter for this this thred. Not only did Hanjour get a commercial certificate in 1999, he was the longest hijacker in the US, dating back to 1990. So your "fairie" tale of an ignorant half baked rube once again fails the reality test. The part where you swallow hook, line and sinker a clearly hyperbole statement. What exactly does "couldn't fly at all" mean, Half Truther? He couldn't flap his arms and become airborne? Since Hanjour already passed all FAA exams in 1999 needed to get his commercial license, the "at all" is clearly false. A more accurate statement is that in 2001, Hanjour didn't care about demonstrating the required skills needed to keep his 1999 commercial pilot license, because that wasn't what he saw his suicide mission needing. And his instructors noted at the time he was not material to demonstrate valid acceptable commercial pilot skills, because he did not care. Finally, as long as you're getting another boxing around your ears, tell me what's so difficult about navigating by punching 4 digits for a suitable VORTAC/DME station into an instrument installed prominently on the cockpit control panel. Are you and your fellow cultists claiming that's too difficult to do any navigation by... For whom, other than yourselves...
#527. To: AGAviator (#521)
It doesn't exist, bullshit artist. There IS no information on Hanjour, the "certificate" was probably entered into the computer by an "associate". There is no record of what school he took lessons from in terms of either a commericial or private pilot's license. It was fabricated apparently. His instructors at the flight simulator school said he couldn't fly at all, and that was reported by the New York Times.
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)
#252. To: buckeroo (#249)
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.
#256. To: AGAviator (#252)
More back pedaling after they themselves use 9.22 seconds as evidenced on Rosie's video clip.
#260. To: FormerLurker, buckeroo, turtle (#256)
You don't judge collapse time for only PART of the building collapsing, you INCLUDE the ENTIRE building from the very top.
#263. To: AGAviator, buckeroo (#260)
You're the people bantering around the "9.22 seconds," "physical impossibility" phrases.
#309. To: FormerLurker, buckeroo, turtle (#263)
(Edited)
Yep, the building SHOULD NOT HAVE collapsed as if it were falling through a vacuum, yet buck's expert "calculated" precisely that.
#316. To: AGAviator (#309)
If a building doesn't fall at close to free fall speeds, its fall has not been set up by controlled demolition. Fifeeen seconds vs. nine seconds for a collapse is not even close to free fall speeds. The controlled demolition theory is debunked by actual and observed free fall speeds indicating lack of thorough setup for a building collapse many times larger than the largest recorded CD.
#318. To: FormerLurker, AGAviator (#316)
All the demolition has to do is START the collapse
#321. To: buckeroo (#318)
But a demolition did not start the collapses. The jet crashes did.
#323. To: FormerLurker (#321)
The buildings did NOT start to fall down when they were hit.
They did NOT start to fall till the precise time they collapsed.
#328. To: buckeroo (#323)
Not much time... it was amazing they stood for so long ... but it took time for the central structure to lose stress capability that caused the later crush down phase.
#331. To: FormerLurker (#328)
what's amazing is that they fell at all
#337. To: buckeroo (#331)
no building is designed to withstand that kind of impact.
#341. To: abraxas (#337)
Also the architect for those buildings claims they were indeed made to endure the impact of a 747.
#346. To: buckeroo (#341)
The twins were designed for a 707 as in a FOG with a velocity well below 550mi/hr. (For you, that means much less inertial force as what occurred on 9/11 by the relative impacts caused by terrorist crashes)
#355. To: James Deffenbach, buckeroo (#346)
#358. To: AGAviator (#355)
You lie, you lose.
#377. To: FormerLurker, buckeroo (#358)
Well then, you've lost long ago
(1) Two aircraft crashes released gigajoules of kinetic energy into the Twin Tower structures, and within 2 hours both structures collapsed from structural damage,
That's just a partial list of the issues about which you and your cotiere have been batted on from one end of the forum to another. There are plenty of others. Your attempts to evade and make things personal is noted, as well as noted as being unsuccessful.
(2) A fireman is recorded on video saying a third WTC Building, WTC7, will be going down because the building is losing its structural stability from crash damage and uncontrolled fires,
(3) Over 30 calls from hijacked aircraft were logged including several by flight attendants giving seat numbers and descriptions of hijackers,
(4) The false statement that Flight 77's cabin door was not opened has been demonstrated to be a lie, as there is no evidence about any cabin door operation of that aircraft either during or before the September 11 flight,
(5) The lauded "peer review publication" of Tw00ferk00ks Steven Jones and Niels Harrit have been shown to be pay-to- publish articles for which $800 was given to a Dhubai publishing mill, with zero other peer reviewed articles
(6) The phrase "pull" as used by the demolition industry means "pull down with cables," and as used by firefighters means "pull back from site,"
(7) Flight 77 impacted a recently-renovated portion of the Pentagon which was not fully occupied and still had construction equipment in place, and
(8) It's a physical impossibliity for a structure to both be flexible enough to absorb gigajoules of energy, move away from vertical centerline, return to vertical centerline on its own, then be rigid enough to provide a fixed platform for a rotating and falling top section to collapse outside the building footprint and
(9) The actual free fall times of the WTC towers have been conclusively shown as 15+ seconds for 1 tower and 22+ seconds for the other, an order of magnitude above the claimed "free fall time" of 9.22 seconds which is supposed to be evidence of a controlled demolition
#431. To: AGAviator (#377)
(7) Flight 77 impacted a recently-renovated portion of the Pentagon which was not fully occupied and still had construction equipment in place
#450. To: FormerLurker (#431)
(Edited)
#452. To: James Deffenbach, buckeroo (#450)
And it is certain that a man who couldn't fly a Cessna could not fly what they claimed hit the Pentagon.
#454. To: AGAviator, abraxas, James Deffenbach, buckeroo (#452)
#464. To: FormerLurker, AGAviator (#454)
Besides LANDING the aircraft short of having his wheels down, AT 530 MPH (which the aircraft basically CAN'T DO), he navigated the plane from Ohio without any navigational aids in terms of ground references, so we must assume he was familiar with IFR (instrument flight rules) procedures using sophisticated flight systems and instruments, where he couldn't even fly a Cessna VFR, (visual flight rules).
At 8:20 AM, Flight 77 took off from Dulles International Airport, 10 minutes after its scheduled departure time. At 8:46, Flight 77 veered severely off course.
At 8:50, the last radio communication was made from the pilots and air traffic control. At 8:56, the jet's transponder was shut off. 1 The pilots' last transmission was "ah direct FALMOUTH American seventy seven thanks." No radio communications from the flight indicated distress. 2 The NTSB report on Flight 77 describes the plane's maneuvers in detail. It began to turn to the south at 8:55, and by 9:00 it was headed east. Shortly thereafter it began to descend from its altitude of 35,000 feet. The autopilot was engaged and disengaged multiple times. At 9:29 the plane was 35 miles west of the Pentagon flying at 7,000 feet. At 9:34 it was about 3.5 miles west-southwest of the Pentagon and started a 330-degree descending right turn, bringing it to an altitude of about 2000 feet four miles southwest of the Pentagon
#465. To: buckeroo (#464)
Why are you bringing up FLT77 on this thread?
#493. To: FormerLurker, buckereoo (#465)
(Edited)
Are you aware of the fact it's practically IMPOSSIBLE to land a 757 at 530 mph, yet this "pilot" who couldn't fly AT ALL according to his instructors was able to pull it off ON THE PENTAGON LAWN
#516. To: AGAviator (#493)
Hanjour got a commercial pilot certificate in 1999.
#521. To: FormerLurker, buckeroo, turtle (#516)
Provide the following information;
Hanjour got a commercial pilot certificate in 1999.
What part of "HE COULDN'T FLY AT ALL" don't you understand?
Replies to Comment # 521. Go to hell and do your own research, Half Truther.
End Trace Mode for Comment # 521.