by Enver Masud
Two World Trade Center, the South Tower, collapsed at 9:59 a.m. One World Trade Center, the North Tower, collapsed at 10:28 a.m. At 10:03 a.m., CNN reported: “Third explosion SHATTERS World Trade Center in New York”. At 10:06 a.m., CNN reported: “Third explosion COLLAPSES World Trade Center in New York”.
According to U.S. government reports, aircraft impact would not have caused the Twin Towers to collapse.
The National Institute of Standards and Technology (NIST), the U.S. government agency responsible for analyzing the collapse of the Twin Towers, included a memo dated February 3, 1964 in Appendix A of their report Baseline Structural Performance and Aircraft Impact Damage Analysis of the World Trade Center Towers (April 26, 2006) that states:
The buildings have been investigated and found to be safe in an assumed collision with a large jet airliner (Boeing 707 – DC 8) traveling at 600 miles per hour. Analysis indicates that such collision would result only in local damage which would not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact.
The memo further states:
The structural analysis carried out by the firm of Worthington, Skilling, Helle & Jackson is the most complete and detailed of any ever made for any building structure.
Executive Summary, Table E-8 of the NIST report estimates aircraft impact speeds at 443 mph plus or minus 30 for AA 11 (WTC 1), and 542 mph plus or minus 24 for UAL 175 (WTC 2).
The Boeing 767s that hit the North and South Towers were slightly heavier than a Boeing 707-. Calculations show that they would have caused less damage than the Boeing 707 travelling at 600 mph in Worthington, Skilling, Helle & Jackson’s structural analysis (Griffin, Debunking 9/11 Debunking, p146) .
Executive Summary, Finding 18 states: “the tower still had reserve capacity after losing a number of columns and floor segments due to aircraft impact.”
Despite the preceding statements, in an August 30, 2006 Fact Sheet, NIST stated:
NIST concluded that the WTC towers collapsed because: (1) the impact of the planes severed and damaged support columns, dislodged fireproofing insulation coating the steel floor trusses and steel columns, and widely dispersed jet fuel over multiple floors; and (2) the subsequent unusually large jet-fuel ignited multi-floor fires (which reached temperatures as high as 1,000 degrees Celsius) significantly weakened the floors and columns with dislodged fireproofing to the point where floors sagged and pulled inward on the perimeter columns. This led to the inward bowing of the perimeter columns and failure of the south face of WTC 1 and the east face of WTC 2, initiating the collapse of each of the towers.”
NIST’s evidence and conclusions are challenged by other experts, and NIST appears to concede to their criticism.
Thomas Eager, professor of materials engineering at MIT, who contributed to the official account of 9/11 says the impact of the airplanes would not have been significant.
Kevin Ryan, a division director who was terminated by Underwriters Laboratories for challenging the NIST analysis, wrote:
Of course, those of us who have actually followed NIST’s investigation know that they could not produce any ‘robust criteria’ to establish that fireproofing was lost through forces of vibration. Instead, NIST performed a shotgun test to see if the fireproofing could have been lost through shearing forces.
The shotgun test not only failed to support NIST’s predetermined conclusions, as was the case for all of their other physical tests, but it actually proved that the fireproofing could not have been sheared off because too much energy would be needed.
The Twin Towers had 240 perimeter columns, and 47 massive, box columns in the core. NIST’s damage assessment for the towers was as follows (Griffin, Debunking 9/11 Debunking, p146):
North Tower: 35 exterior columns severed, 2 heavily damaged; 6 core columns severed, 3 heavily damaged; 43 of 47 core columns stripped of insulation on one or more floors.
South Tower: 33 exterior columns severed, 1 heavily damaged; 10 core columns severed, 1 heavily damaged; 39 of 47 core columns stripped of insulation on one or more floors.
Engineering News-Record explained in 1964:
one could cut away all the first story columns on one side of the building, and part way from the corners of the perpendicular sides, and the building could still withstand design live loads, and a 100 mph wind force from any direction.
To make the Commission’s theory appear plausible, The 9/11 Commission Report claims (541), falsely, that the core of the towers “was a hollow steel shaft.”
In response to an April 12, 2007 “Request for Correction,” NIST’s Catherine S. Fletcher, Chief, Management and Organization Division, appears to concede—at least partially—to the critics.
In her letter dated September 27, 2007, she states:
NIST Computer Simulations: NIST has used an extensive database of photographic and video evidence to validate the models used to analyze the behavior of the towers up to the point of initiation of collapse. . . .
The WTC Steel Temperature: While NIST did not find evidence that any of the recovered core columns experienced temperatures in excess of 250° C, it is not possible to extrapolate from such a small sample size to state that none of the core columns on the fire affected floors reached temperatures in excess of 250° C. . . .
The Goal of the WTC Report and Its Overall Analysis: NIST has stated that it did not analyze the collapse of the towers. NIST carried its analysis to the point where the buildings reached global instability. . . . we were unable to provide a full explanation of the total collapse.
NIST’s analysis ends with the “initiation of collapse.” NIST admits that “it did not analyze the collapse of the towers.”
In room fires (Dr. Vytenis Babrauskas, 2006)
the maximum value which is fairly regularly found . . . turns out to be around 1200°C, although a typical post-flashover room fire will more commonly be 900~1000°C. The time-temperature curve for the standard fire endurance test, ASTM E 119 goes up to 1260°C, but this is reached only in 8 hr.
NIST also admits that physical evidence does not support their conclusion of fire temperatures as high as 1,000 degrees Celsius. In the samples taken from the site, there’s no evidence that any core column experienced temperatures in excess of 250° C.
Since steel loses 50% strength at 650° C, and melts at 1500° C, if one were to assume—for the sake of argument only—that the fire was large enough, the fire was neither hot enough, nor long-lasting enough (major fires lasted less than15 minutes), to significantly weaken the towers
Richard Gage, founder of Architects and Engineers for 9/11 Truth—with 400-plus members, makes the following points regarding the NIST report:
The destruction occurred with rapid onset, at virtually free-fall speed, and with radial symmetry.
One hundred eighteen first responders described hearing, seeing and feeling explosions and seeing flashes of light at the onset of destruction.
The concrete floors were almost completely pulverized into dust and gravel.
The structural steel framework was largely dismembered into shippable lengths. Much of it was hurled outside the Twin Towers’ perimeters, some as far as 500 feet away.
Tons of molten metal were seen by FDNY and others, and was described as “flowing like lava” for weeks after 9/11, yet its existence was denied by NIST.
Proven chemical evidence of thermate, an incendiary material which produces molten iron as its by-product, found on the columns and beams, previously molten metal, and iron-rich micro-spheres in the dust by Dr. Steven Jones (and corroborated by the U.S. Geological Survey, but never explained).
“These features are characteristic of controlled demolitions, and not office or jet fuel fires”, writes Gage.
And explosions were reported on television news.
MSNBC Reporter: At 10:30 I tried to leave the building, but as soon as I got outside, I saw [sic] the second explosion, an another rumble, and more dust. I ran inside the building . . . and then a fire marshall came in and said we had to leave because if there was a third explosion this building might not last.
CBS Channel 2 Reporter: New York’s bravest never had a chance.
Firefighter on CBS Channel 2: We never got that close to the building. The explosion blew, and it knocked everybody over.
Fox News Reporter: The FBI is here as you can see . . . they were taking photographs and securing this area just prior to that huge explosion that we all heard and felt.
NBC Reporter: Most of the victims so far were outside the blownup building.
Witness on NBC: It sounded like gunfire—bang, bang, bang, bang. Then all of a sudden three big explosions.
Among those who testified to explosions at the 9/11 Commission hearings was William Rodriguez, “honored by the White House” for his rescue efforts.
Since the force exerted by the impact of the aircraft was within the Twin Towers’ design criteria, and the fires were neither hot enough, large enough, nor long-lasting enough to have caused the collapse, there had to have been another source of energy to cause collapse.
Leslie Robertson, structural engineer responsible for the design of the World Trade Center, is reported to have said at the National Conference of Structural Engineers on October 5, 2001: “As of 21 days after the attack, the fires were still burning, and molten steel was still running.”
In their investigation, both the 9/11 Commission and NIST, ignored testimony and evidence not consistent with their collapse theory.
NIST says (FAQ, August 30, 2006):
The condition of the steel in the wreckage of the WTC towers (i.e., whether it was in a molten state or not) was irrelevant to the investigation of the collapse since it does not provide any conclusive information on the condition of the steel when the WTC towers were standing.
The molten steel may not provide “any conclusive information on the condition of the steel when the WTC towers were standing”, but it is very relevant to the evaluation of hypotheses of why the towers collapsed. The steel at the bottom of the debris pile did not spontaneously get hot and melt after collapse.
NIST did not evaluate the use of explosives.
NIST rejects the “pancake theory” for the collapse (August 30, 2006 Fact Sheet) popular in some circles, but NIST lead investigator Shyam Sunder contradicts NIST.
Sunder says that the squibs (puffs or jets of smoke and dust caused by the detonation of explosives) seen in videos of the collapse are caused by the “floor pancaking” (Popular Mechanics, March 2007).
In September 2006, Mete Sozen and Christoph M. Hoffmann, professors at Purdue University, claimed to have an answer.
Sozen and Hoffman concluded that
the weight of the fuel acted like a flash flood of flaming liquid, knocking out essential structural columns within the building and removing fireproofing insulation from other support structures.
These researchers simulated the “top 20 stories” for “3/4 seconds real-time”. Their simulation, like NIST’s, says nothing about the collapse itself—it stops at the initiation of collapse.
By extrapolation, a simulation of the 102 real-time minutes from impact to collapse—which would have to make many arguable assumptions—could take 652,800 hours or about 75 years.
Even though the “criminal code requires that crime scene evidence be kept for forensic analysis. FEMA had steel recovered from the building rubble destroyed or shipped” to India and China before it could be examined for traces of explosives (sourcewatch.org).
A paper by Niels H. Harrit and others (The Open Chemical Physics Journal) has confirmed the presence of thermitic material in dust samples from the WTC.