Cohen, Arianne
World Trade Center 7 Report Puts 9/11 Conspiracy Theory to Rest
Conspiracy theorists have long claimed that explosives downed World Trade Center 7, north of the Twin Towers. The long-awaited report from the National Institute of Standards and Technology (NIST) conclusively rebuts those claims. Fire alone brought down the building, the report concludes, pointing to thermal expansion of key structural members as the culprit. The report also raises concerns that other large buildings might be more vulnerable to fire-induced structural failure than previously thought.
GAITHERSBURG, Maryland -- The National Institute of Standards and Technology (NIST) has released its long-awaited report on the collapse of World Trade 7 following the attacks of Sept. 11, 2001. "Our take-home message today is that the reason for the collapse of World Trade Center 7 is no longer a mystery," NIST lead investigator Shyam Sunder told journalists at this morning's press conference in Gaithersburg, Md. "WTC 7 collapsed because of fires fueled by office furnishings. It did not collapse from explosives or from diesel fuel fires."
Conspiracy theorists have long pointed to the collapse of the 47-story structure as key evidence that the U.S. government orchestrated or abetted the 9/11 attacks. No planes struck the building, and the commonly available views of the exterior didn't show significant damage. Yet, at 5:20 pm, 7 hours after the collapse of the Twin Towers (WTC 1 and 2), WTC 7 rapidly fell in on itself. Since WTC 7 housed Secret Service and CIA offices, conspiracy theorists claimed that the building was destroyed in a controlled demolition in order to obliterate evidence of the U.S. government's complicity in the terrorist attacks. "It is impossible for a building to fall the way it fell without explosives being involved," stated actress and TV personality Rosie O'Donnell of ABC's The View in March 2007. "For the first time in history, steel was melted by fire. It is physically impossible," she said.
Today's report confirms that a fire was, indeed, the cause. "This is the first time that we are aware of, that a building taller than about 15 stories has collapsed primarily due to fires," Sunder told reporters at the press conference. "What we found was that uncontrolled building fires--similar to fires experienced in other tall buildings--caused an extraordinary event, the collapse of WTC7." The unprecedented nature of the event means that understanding the precise mechanism of the collapse is important not just to answer conspiracy theorists' questions, but to improve safety standards in the engineering of large buildings.
The final report describes how debris from the collapse of WTC 1 ignited fires on at least 10 floors of WTC 7 at the western half of the south face. Fires on Floors 7 through 9 and 11 through 13 burned out of control, because the water supply to the automatic sprinkler system had failed. The primary and backup water supply to the sprinkler systems for the lower floors relied on the city's water supply. Those water lines were damaged by the collapse of WTC 1 and 2. These uncontrolled fires in WTC 7 eventually spread to the northeast part of the building, where the collapse began.
After 7 hours of uncontrolled fires, a steel girder on Floor 13 lost its connection to one of the 81 columns supporting the building. Floor 13 collapsed, beginning a cascade of floor failures to Floor 5. Column 79, no longer supported by a girder, buckled, triggering a rapid succession of structural failures that moved from east to west. All 23 central columns, followed by the exterior columns, failed in what's known as a "progressive collapse"--that is, local damage that spreads from one structural element to another, eventually resulting in the collapse of the entire structure.
The report clarifies a number of widely debated issues concerning the collapse, particularly the role of the building's many diesel fuel tanks and the importance of structural damage from falling WTC 1 debris. Both of those factors have been cited by investigators as possibly contributing to the collapse; the 2006 Popular Mechanics book Debunking 9/11 Myths: Why Conspiracy Theories Can't Stand Up to the Facts mentions both hypotheses. However, the final NIST report downplays both scenarios, concluding that the diesel fuel stored in tanks (and intended to power backup generators) did not burn long enough or hot enough to account for structural failures. And, while debris damage to WTC 7's southern exterior was considerable (and initiated the destructive fires), the collapse originated in the northeast portion of the building. In fact, the report concludes: "Even without the structural damage, WTC 7 would have collapsed from fires."
The report determines that the actual culprit in the collapse was the combustion of ordinary building furnishings: "These uncontrolled fires had characteristics similar to those that have occurred previously in tall buildings." If the sprinkler system in WTC 7 had been working, it is likely that "the fires in WTC 7 would have been controlled and the collapse prevented." The report also suggests that current engineering standards for coping with fire-induced thermal expansion need to be re-examined, particularly for buildings like WTC 7 that have long, unsupported floor spans. A key factor in the collapse, NIST concluded, was the failure of structural "connections that were designed to resist gravity loads, but not thermally induced lateral loads." According to Sunder: "For the first time we have shown that fire can induce a progressive collapse."
Spurred by conspiracy theorists' questions, investigators did look specifically at the possibility that explosives were involved. "Hypothetical blast events did not play a role in the collapse of WTC 7," the report states, adding that investigators "found no evidence whose explanation required invocation of a blast event." Moreover, the smallest charge capable of initiating column failure "would have resulted in a sound level of 130 dB [decibels] to 140 dB at a distance of at least half a mile." Witnesses did not report hearing such a loud noise, nor is one audible on recordings of the collapse.
NIST will accept public comment on the final report until Sept. 15, 2008.
NIST's press release and other material on the report can be found here. Click here to download the full report in pdf form.
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another piece by A. Cohen
http://www.popularmechanics.com/technology/engineering/architecture/4278...
6 Debunked 9/11 Conspiracy Claims From NIST's New WTC 7 Report
Shyam Sunder, the lead investigator on the National Institute of Standards and Technology (NIST) report, responded directly to many conspiracy claims this morning at his press conference in NIST headquarters in Gaithersburg, Md.
By Arianne Cohen
GAITHERSBURG, Maryland -- Shyam Sunder, the lead investigator on the National Institute of Standards and Technology (NIST) report, responded directly to many conspiracy claims here this morning at his press conference in NIST headquarters in Gaithersburg, Md., which was attended by mainstream media and a handful of conspiracy theorist media, including a representative from InfoWars.com, a Web site that puts forward9/11 conspiracy theories. Sunder specifically addressed conspiracy claims linked to WTC 7. "Before I tell you what we found, I'd like to tell you what we did not find," Sunder told reporters. "We did not find any evidence that explosives were used to bring the building down. The collapse was also not due to fires from the substantial amount of diesel fuel stored in the buildings."
Here is a summary of some common 9/11 conspiracy theory claims regarding WTC 7, along with NIST's response:
Claim: "No combination of debris damage, fuel-tank explosions and fires could inflict the kind of simultaneous damage to all the building's columns required to make the building implode," says WTC7.net, a Web site dedicated to conspiracy theories. "The precision of such damage required to bring Building 7 down into its footprint was especially great, given the ratio of its height to its width and depth."
NIST report and press conference: Fire did indeed inflict enough column damage to destroy the building through a previously undocumented collapse sequence of thermal expansion. "Anyone who has run a tight jar lid under water to help loosen it knows that the metal expands when it gets hot," Sunder said. "Heat also causes steel to lose strength and stiffness. Thermal expansion occurs at temperatures much lower than those required to reduce steel strength and stiffness." The report found that as WTC 7's steel beams expanded in the heat, numerous structural connections throughout the building failed. That weakened the structure even before the collapse of any vertical columns.
Claim: The shape of the building's tidy pile of wreckage is consistent with a demolition, conspiracy theorists say.
NIST report and press conference: Sunder agrees that the wreckage was tidy and explained why. "If you look at columns 79, 80 and 81 [three of the building's central columns], the floor area that they're carrying is very large--particularly column 79, which was carrying about 2000 sq. ft. of floor area." Column 79 was the first column to fail. "It was an interior column that failed, followed by two more interior columns [80 and 81], then east to west. So what you're seeing is an interior collapse, then to the outside. What you're getting is an impression of a controlled demolition, but it's not."
Claim: The way the building fell was caused by demolition or thermate. (Thermate is thermite mixed with sulfur and sometimes other chemicals, which produces brief but intense and highly localized incendiary effects.)
NIST report and press conference: Sunder said that his team investigated these hypothetical causes and ruled them out. "We asked ourselves what is the minimum amount of charge we could use to bring the building down," he said. "And we found that even the smallest charge would release an extremely loud sound heard half a mile away." There were no reports of such a sound; numerous observers and video recordings found the collapse to be relatively quiet.
Prominent conspiracy theorist Steven Jones and others have suggested that thermate could have been inserted into a column, exploding the column without the loud boom of a demolition. Sunder said his team considered that theory. "In order for the thermate reaction to melt steel to take place, there has to be materials. If you look at the amount needed--at least 100 pounds for one column--you need someone to get that amount in the building, and place it, and for the reaction to take place. It is unlikely."
Claim: At the press conference, theorists questioned why NIST had just now found a previously undocumented cause of building collapse.
NIST report and press conference: The particulars of WTC 7's design contributed to the thermal expansion. WTC 7 had floor spans up to 54 ft. long. "Longer beams can be subject to proportionally greater expansion effects," Sunder noted. "Other tall buildings have burned for as long or longer in similar fires without collapsing--when sprinklers either did not exist or were not functional. So we knew from the beginning of our study that understanding what happened to Building 7 on 9/11 would be difficult. It did not fit any textbook description that you could readily point to and say, yes, that's why the building failed." The issue, Sunder said, was that buildings are not typically tested for their structural response to fire.
Claim: The minimal wreckage available for later investigation has generated speculation. Some conspirators point to the fast removal of debris as evidence of a government coverup.
NIST report and press conference: Compared to WTC 1 and 2, NIST had very little WTC 7 wreckage to study. The site was cleared quickly in a search-an- rescue effort, and much of the debris was transported to salvage yards. "There was no loss of life," Sunder noted. "In hindsight, we knew that the building was evacuated. But we didn't know that on that day." Hundreds of investigators at the salvage yards later found that the Twin Towers' steel columns were labeled and numbered, while the columns from Towers 5, 6 and 7 were not. "I am not surprised that there wasn't a lot of identifiable debris," Sunder said. "But at the time, we were concerned about terrorists who attacked our country and search and rescue. I think the fact that they [invesigators] didn't collect [wreckage] was the least important activity that happened that day."
Claim: Many theorists have suggested that the long delay in an explanatory report is further proof of a government coverup.
NIST and press conference: NIST first had to complete the investigation on the collapse of the Twin Towers and publish its report before turning to WTC 7. The Twin Towers report was released in September 2005. "We thought we might be able to do things much quicker and faster because of our tower experience," Sunder said. "I think we underestimated the amount of effort that would be required to answer the questions that we raised." In addition, new computer models of the collapse had to be created. "A typical fire simulation for a single floor of the building took up to two days with a state-of-the-art cluster of Linux computers. We had computer programs that took six to eight months to get a correct run, and we wanted to make sure we got this right. And three years is not an unusual length of time." Sunder emphasized that previous reports were preliminary and provisional. "We didn't have the insight that thermal expansion could have happened until early last year," Sunder said. "After that it was smooth sailing." Until last year, NIST was still investigating other hypotheses, including whether the building's location on top of an electric substation played a critical role and whether 6000 gal. of diesel fuel used to power backup generators in the building directly weakened the columns. Both hypotheses were abandoned.
Sunder classified the report's conclusions as "simple, straightforward, elegant and going along with what was observed. I would say that the findings we have are incredibly conclusive that fire is why WTC 7 collapsed."
http://www.popularmechanics.com/technology/engineering/architecture/4278...
contributed to the pop mech book...
http://books.google.com/books?id=3C7JSfnMsbIC&pg=PR9&lpg=PR9&dq=arianne+...
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