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Context of 'August 21, 2008: NIST Announces Conclusions of WTC 7 Investigation, Presents New Theory for Collapse'

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Numerous witnesses, including firefighters and other rescue workers, hear explosions at the start of, and during, the collapse of the south WTC tower. Some of them report hearing a single explosion:
bullet Jeff Birnbaum: “There was an explosion and the whole top leaned toward us and started coming down.” [Electrical Wholesaling, 2/1/2002]
bullet Battalion Chief John Sudnik: “[W]e heard a loud explosion or what sounded like a loud explosion and looked up and I saw Tower Two start coming down.” [City of New York, 11/7/2001]
bullet Firefighter Edward Kennedy hears “a tremendous boom, explosion… and the top of the building was coming down at us.” [City of New York, 1/17/2002]
bullet Firefighter Edward Sheehey hears “an explosion, looked up, and the building started to collapse.” [City of New York, 12/4/2001]
bullet Battalion Chief Thomas Vallebuona: “I heard ‘boom,’ an exploding sound, a real loud bang. I looked up, and I could see the Trade Center starting to come down.” [City of New York, 1/2/2002]
bullet EMT Julio Marrero: “I heard a loud bang. We looked up, and we just saw the building starting to collapse.” [City of New York, 10/25/2001]
Other witnesses report hearing multiple explosions:
bullet Journalist Pete Hamill: “We heard snapping sounds, pops, little explosions, and then the walls bulged out, and we heard a sound like an avalanche.” [New York Daily News, 9/11/2001]
bullet Police officer Sue Keane, who is an Army veteran, is located in the north WTC tower: “[I]t sounded like bombs going off. That’s when the explosions happened.… It started to get dark, then all of a sudden there was this massive explosion.” [Hagen and Carouba, 2002, pp. 65]
bullet Firefighter Keith Murphy, who is in the lobby of the North Tower: “[T]he first thing that happened, which I still think is strange to me, the lights went out.… I had heard right before the lights went out, I had heard a distant boom boom boom, sounded like three explosions.… At the time, I would have said they sounded like bombs, but it was boom boom boom and then the lights all go out.… I would say about 3, 4 seconds, all of a sudden this tremendous roar.” [City of New York, 12/5/2001]
bullet Firefighter Craig Carlsen hears “explosions coming from building two, the South Tower. It seemed like it took forever, but there were about ten explosions.… We then realized the building started to come down.” [City of New York, 1/25/2002]
bullet Firefighter Thomas Turilli, who is in the lobby of the North Tower: “[A]ll of a sudden you just heard like it almost actually that day sounded like bombs going off, like boom, boom, boom, like seven or eight, and then just a huge wind gust just came… It just seemed like a huge explosion.” [City of New York, 1/17/2002]
bullet Firefighter Stephen Viola: “[T]hat’s when the South Tower collapsed, and it sounded like a bunch of explosions. You heard like loud booms.” [City of New York, 1/10/2002]
bullet Firefighter Lance Lizzul: “[W]e heard some bangs. That made us look up, and that’s when the first Trade Center came down.” [City of New York, 12/10/2001]
bullet Paramedic Kevin Darnowski: “I heard three explosions, and then we heard like groaning and grinding, and Tower Two started to come down.” [City of New York, 11/9/2001]
However, the National Institute of Standards and Technology, which conducts a three-year study of the WTC collapses, will subsequently claim it found “no corroborating evidence for alternative hypotheses suggesting that the WTC towers were brought down by controlled demolition using explosives” (see October 26, 2005). [National Institute of Standards and Technology, 9/2005, pp. 146]

Entity Tags: Julio Marrero, Stephen Viola, John Sudnik, Craig Carlsen, Ed Kennedy, Keith Murphy, Kevin Darnowski, Pete Hamill, Edward Sheehey, World Trade Center, Lance Lizzul, Thomas Vallebuona, Sue Keane, Jeff Birnbaum, Thomas Turilli

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

World Trade Center Building 7 (WTC 7) suffers fires on several floors, some of which last until 5:20 p.m., when the building collapses. [National Institute of Standards and Technology, 8/21/2008] WTC 7 is a 47-story office building located just north of the Twin Towers. It is damaged when the north WTC tower (WTC 1) collapses at 10:28 a.m. (see 10:28 a.m. September 11, 2001). [National Institute of Standards and Technology, 11/2008, pp. 2, 16]
Fires Started by Collapse Debris - Two official reports on the collapse of WTC 7 will tentatively conclude that fires in this building are initiated by debris that is ejected when the North Tower collapses (see 10:28 a.m. September 11, 2001). In a 2002 report (see May 1, 2002), the Federal Emergency Management Agency (FEMA) will state, “It is likely that fires” in WTC 7 “started as a result of debris from the collapse of WTC 1.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-20] In a 2008 report (see November 20, 2008), the National Institute of Standards and Technology (NIST) will state, “Most likely, the WTC 7 fires began as a result of burning debris from the collapse of WTC 1.” However, NIST will add, “visual evidence of fires in the building was not available until around noon.” [National Institute of Standards and Technology, 11/2008, pp. 18]
Fires Spread in WTC 7 - According to NIST, fires are ignited “on at least 10 floors” of WTC 7, but “only the fires on floors 7 through 9 and 11 through 13 grew and lasted until the time of the building collapse.” [National Institute of Standards and Technology, 11/2008, pp. xxxvi] NIST will state, “Early fires were seen on the southwest corner of floors 19, 22, 29, and 30 shortly after noon,” but “These were short-lived.” [National Institute of Standards and Technology, 11/2008, pp. 51] The fires on floors 7 to 9 and 11 to 13, however, “grew and spread, since they were not extinguished either by the automatic sprinkler system or by [the New York City Fire Department], because water was not available in WTC 7.” Fires are “generally concentrated on the east and north sides of the northeast region beginning at about 3 p.m. to 4 p.m.” [National Institute of Standards and Technology, 11/2008, pp. 21] The fires on floors 7 to 9 and 11 to 13 have “characteristics similar to those that have occurred previously in tall buildings,” according to NIST, and “Their growth and spread [are] consistent with ordinary building contents fires.” [National Institute of Standards and Technology, 11/2008, pp. xxxvi] These fires are “fed by combustibles (e.g., desks, chairs, papers, carpet) that were ordinary for commercial occupancies.” However, NIST will point out, there is “no evidence that the fires spread from floor to floor, except, perhaps, just prior to the collapse of the building.” [National Institute of Standards and Technology, 11/2008, pp. 51-52]
Limited Evidence Available - Both FEMA and NIST will admit that their accounts of the fires in WTC 7 are based upon imperfect evidence. In its report on the WTC collapses, published in May 2002, FEMA will note, “Currently, there is limited information about the ignition and development of fires at WTC 7.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-20] In the final report of its investigation of the collapse of WTC 7, NIST will point out that “available images showing fires in WTC 7 did not allow the detailed description of fire spread that was possible for the WTC towers.” The report will add: “It must be kept in mind that [NIST’s] fire observations were based on images of the exterior faces, which provided little indication about the behavior of fires well removed from the exterior walls. It is likely that much of the burning took place beyond the views of the windows.” But, the report will state, “[T]here was sufficient information to derive general descriptions of fire ignition and spread on various floors of the building.” [National Institute of Standards and Technology, 11/2008, pp. 18]
NIST Blames Fires for Collapse - WTC 7 collapses at 5:20 p.m. this afternoon (see (5:20 p.m.) September 11, 2001). In late 2008, at the end of its investigation into WTC 7’s collapse, NIST will blame the fires WTC 7 suffers for causing its collapse (see August 21, 2008 and August 21, 2008). NIST will state: “The heat from the uncontrolled fires caused steel floor beams and girders to thermally expand, leading to a chain of events that caused a key structural column to fail. The failure of this structural column then initiated a fire-induced progressive collapse of the entire building.” [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 11/2008, pp. xxxvi-xxxvii] However, critics will dispute this conclusion, instead blaming explosives for the collapse (see August 21, 2008). [New York Times, 8/21/2008] FEMA will offer no firm conclusions about the possible role fires play in causing WTC 7 to collapse. In its 2002 report it will state, “The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-31]

Entity Tags: World Trade Center, National Institute of Standards and Technology, Federal Emergency Management Agency

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Jeffrey Scott Shapiro.Jeffrey Scott Shapiro. [Source: University of Florida]Larry Silverstein, who recently took over the lease of the World Trade Center complex (see July 24, 2001), discusses possibly bringing down WTC Building 7 in a controlled demolition in a telephone conversation with his insurance carrier, according to a reporter who is at the WTC site this afternoon. [Fox News, 4/22/2010] WTC 7 is a 47-story office building located just north of the Twin Towers. The National Institute of Standards and Technology (NIST) will say it suffered some structural damage (see 10:28 a.m. September 11, 2001) when the North Tower collapsed (see 10:28 a.m. September 11, 2001) and it has fires on several floors (see (10:28 a.m.-5:20 p.m.) September 11, 2001). It will collapse at 5:20 p.m., apparently becoming the first tall building ever to come down primarily as a result of fire (see (5:20 p.m.) September 11, 2001). [National Institute of Standards and Technology, 11/2008, pp. xxxv-xxxvi]
Silverstein Allegedly Wants WTC 7 Demolished - Investigative reporter Jeffrey Scott Shapiro, who is at the scene of the attacks in New York, will later recall: “Shortly before [WTC 7] collapsed, several NYPD officers and Con Edison workers told me that Larry Silverstein… was on the phone with his insurance carrier to see if they would authorize the controlled demolition of the building, since its foundation was already unstable and expected to fall. A controlled demolition would have minimized the damage caused by the building’s imminent collapse and potentially save lives.” Shapiro will add: “Many law enforcement personnel, firefighters, and other journalists were aware of this possible option. There was no secret.” [Fox News, 4/22/2010] Preparing a large building for demolition usually takes weeks, or even months. This time is spent on operations such as wrapping concrete columns to ensure pieces do not fly off. [Baltimore Sun, 2/26/1995; PBS NOVA, 12/1996; Construction Equipment Guide, 2/24/2005]
Discussion of Demolition Later Denied - Silverstein will later recall discussing WTC 7 over the phone with the commander of the New York Fire Department, and telling him, “We’ve had such terrible loss of life, maybe the smartest thing to do is pull it” (see After 12:00 Noon September 11, 2001), but a spokesman will subsequently claim that Silverstein was referring to withdrawing firefighters from the building, not bringing WTC 7 down with explosives. [US Department of State, 9/16/2005; BBC, 7/4/2008] At the end of a three-year investigation into the building’s collapse, NIST will say WTC 7 “did not collapse from explosives,” but critics will dispute this conclusion (see August 21, 2008). [Associated Press, 8/21/2008; New York Times, 8/21/2008]

Entity Tags: Jeffrey Scott Shapiro, New York City Police Department, Con Edison, World Trade Center, Larry Silverstein

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

A four-image progression of photos showing World Trade Center Building 7 collapsing down into its footprint.A four-image progression of photos showing World Trade Center Building 7 collapsing down into its footprint. [Source: unknown] (click image to enlarge)Building 7 of the World Trade Center complex, a 47-story tower, collapses. No one is killed. [CNN, 9/12/2001; Washington Post, 9/12/2001; MSNBC, 9/22/2001; Associated Press, 8/21/2002] It collapses in 6.6 seconds, which is just 0.6 of a second longer than it would have taken a free-falling object dropped from its roof to hit the ground. [Deseret Morning News, 11/10/2005] Many questions will arise over the cause of its collapse in the coming months and years. Building 7, which was not hit by an airplane, is the first modern, steel-reinforced high-rise to collapse because of fire. [Chicago Tribune, 11/29/2001; Stanford Report, 12/5/2001; New York Times, 3/2/2002] Some will later suggest that the diesel fuel stored in several tanks on the premises may have contributed to the building’s collapse. The building contained a 6,000-gallon tank between its first and second floors and another four tanks, holding as much as 36,000 gallons, below ground level. There were also three smaller tanks on higher floors. [Chicago Tribune, 11/29/2001; New York Times, 3/2/2002; New York Observer, 3/25/2002; Federal Emergency Management Agency, 5/1/2002, pp. 1-17] However, the cause of the collapse is uncertain. A 2002 government report will conclude: “The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence.” [Federal Emergency Management Agency, 5/1/2002, pp. 1-17] Some reports indicate that the building may have been deliberately destroyed. Shortly after the collapse, CBS News anchor Dan Rather comments that the collapse is “reminiscent of… when a building was deliberately destroyed by well-placed dynamite to knock it down.” [CBS News, 9/11/2001] And moments after the collapse, MSNBC’s Brian Williams joins David Restuccio, an FDNY lieutenant, by phone to ask him about the collapse. “You guys knew this was coming all day?” asks Williams. Restuccio replies: “We had heard reports that the building was unstable, and that it would eventually need to come down on its own, or it would be taken down. I would imagine it came down on its own.” Restuccio does not explain what he means by “it would be taken down.” [MSNBC, 9/11/2001]

Entity Tags: Dan Rather, World Trade Center, David Restuccio

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Steel beams from the WTC were already being removed and recycled on September 20, 2001.Steel beams from the WTC were already being removed and recycled on September 20, 2001. [Source: Associated Press]In the month following 9/11, a significant amount of the steel debris from the WTC collapses is removed from the rubble pile, cut into smaller sections, and either melted at a recycling plant or shipped out of the US. [US Congress, 3/6/2002] Each of the Twin Towers contained 78,000 tons of recyclable steel. Much of this is shipped to India, China, and other Asian countries, where it will be melted down and reprocessed into new steel products. Asian companies are able to purchase the steel for just $120 per ton, compared, for example, to a usual average price of $150 per ton in China. Industry officials estimate that selling off the steel and other metals from the WTC for recycling could net a few tens of million dollars. [New York Times, 10/9/2001; Reuters, 1/21/2002; Reuters, 1/22/2002; Eastday, 1/24/2002; CorpWatch, 2/6/2002] 9/11 victims’ families and some engineers are angered at the decision to quickly discard the steel, believing it should be examined to help determine how the towers collapsed. A respected fire fighting trade magazine comments, “We are literally treating the steel removed from the site like garbage, not like crucial fire scene evidence.” [Fire Engineering, 1/2002] Rep. Joseph Crowley (D-NY) will later call the loss of this evidence “borderline criminal.” By March 2002, 150 pieces of steel from the WTC debris will have been identified by engineers for use in future investigations (see March 6, 2002). [Federal Emergency Management Agency, 5/1/2002, pp. D-13] A study by the National Institute of Standards and Technology (NIST), which commences in August 2002 [National Institute of Standards and Technology, 8/21/2002; Associated Press, 8/21/2002] , will have 236 pieces of recovered steel available to it. Of these, 229 pieces are from WTC 1 and 2, representing “roughly 0.25 percent to 0.5 percent of the 200,000 tons of structural steel used in the construction of the two towers.” [National Institute of Standards and Technology, 9/2005, pp. 85 pdf file] New York Mayor Mike Bloomberg defends the decision to quickly get rid of the WTC steel, saying, “If you want to take a look at the construction methods and the design, that’s in this day and age what computers do. Just looking at a piece of metal generally doesn’t tell you anything.” Officials in the mayor’s office decline to reply to requests by the New York Times regarding who decided to have the steel recycled. [New York Times, 12/25/2001; Eastday, 1/24/2002]

Entity Tags: Joseph Crowley, World Trade Center, Michael R. Bloomberg

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

FEMA’s World Trade Center Building Performance Study.FEMA’s World Trade Center Building Performance Study. [Source: FEMA]FEMA releases its report of the WTC collapses. It concludes, “[W]ith the information and time available, the sequence of events leading to the collapse of each tower could not be definitively determined.” On Building 7: “The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time.” [Federal Emergency Management Agency, 5/1/2002]

Entity Tags: World Trade Center, Federal Emergency Management Agency

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

The National Institute of Standards and Technology (NIST)—an agency of the US Commerce Department’s Technology Administration—announces details of its forthcoming investigation into the collapses of the World Trade Center Twin Towers and Building 7 on 9/11. The NIST investigation aims “to investigate the building construction, the materials used, and the technical conditions that contributed to the outcome of the World Trade Center (WTC) disaster.” It also aims to examine the activities of building occupants and emergency responders on 9/11, studying such issues as emergency communications within the WTC, the movement of people during the evacuations, and issues around persons with disabilities. Leading technical experts from industry, academia, and other laboratories, alongside NIST’s own expert staff, will participate in the investigation. Expert professionals from the private sector will also be involved. Glenn Corbett, a fire science professor at John Jay College, says, “This is going to be the most extensive building disaster investigation ever performed.” [Associated Press, 8/21/2002; National Institute of Standards and Technology, 8/21/2002; National Institute of Standards and Technology, 8/3/2005] The investigation is formally authorized in October 2002, when the National Construction Safety Team Act is signed into law. The act, which gives NIST authorization to investigate major building failures in the US, is written largely as a result of the World Trade Center collapses. [National Institute of Standards and Technology, 10/2/2002; New York Times, 5/8/2003] NIST’s investigation is originally proposed to last two years, with a budget of $16 million. [National Institute of Standards and Technology, 8/21/2002] However, it eventually will last three years, with its final report into the collapses of the Twin Towers being released in October 2005 (see October 26, 2005). A previous analysis of the WTC collapses conducted by FEMA and the American Society of Civil Engineers (ASCE) was completed earlier in 2002 (see May 1, 2002), but this had a budget of just $1.1 million. By the time NIST starts its investigation, much of the crucial steel debris from the WTC collapses has already been destroyed (see September 12-October 2001). They later refer to there being a “scarcity of physical evidence that is typically available in place for reconstruction of a disaster.” [National Institute of Standards and Technology, 9/2005, pp. xxxvi]

Entity Tags: World Trade Center, National Institute of Standards and Technology, Glenn Corbett

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

During the course of its three-year investigation of the World Trade Center collapses, the National Institute of Standards and Technology (NIST) performs computer simulations of the behavior of each WTC tower on 9/11. In its final report, released in October 2005 (see October 26, 2005), it will describe having determined which variables most affected the outcome of its various simulations. Then, “[f]or each of the most influential variables, a central or middle value and reasonable high and low values were identified.” However, “[u]pon a preliminary examination of the middle cases, it became clear that the towers would likely remain standing. The less severe cases were discarded after the aircraft impact results were compared to observed events. The middle cases… were discarded after the structural response analysis of major subsystems were compared to observed events.” Therefore, the “more severe case… was used for the global analysis of each tower.” But, to “the extent that the simulations deviated from the photographic evidence or eyewitness reports, the investigators adjusted the input, but only within the range of physical reality.” [National Institute of Standards and Technology, 9/2005, pp. 143-144]

Entity Tags: National Institute of Standards and Technology, World Trade Center

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Matthys Levy.Matthys Levy. [Source: PBS]A report is made publicly available, which the Engineering News-Record calls the “most comprehensive study yet on the destruction of the World Trade Center.” The study was commissioned by WTC leaseholder Silverstein Properties Inc. to support a $7 billion insurance claim, and conducted by a team of engineers from several leading firms, including Weidlinger Associates, LZA Technology/Thornton-Tomasetti, and ARUPFire. It is intended to build on a previous study sponsored by FEMA (see May 1, 2002). The report’s findings are based on an analysis of original structural drawings, thousands of photos, and dozens of videos. Investigators used fire evaluation techniques and powerful computer software to simulate the condition of each tower at critical times between the planes’ impacts and the towers’ collapses. The earlier FEMA investigators had no access to such computer modeling. Matthys Levy, the chairman of Weidlinger Associates and one of the engineers on the study team, says, “The buildings had tremendous reserve capacity and that was reflected in all of the elements we analyzed. In fact, because there were so much excess capacity, the columns even in the impact floors did not buckle immediately, but failed as the result of the fire.” The report states that failure of the WTC’s steel floor supports (“trusses”) did not contribute to the collapses. Instead, the collapses were caused by the failure of steel structural columns that were either destroyed when the planes hit or lost fireproofing, leaving them vulnerable to the weakening effects of the ensuing fires. It says that debris and dust distributed by the plane crashes inhibited the fires, such that the average air temperatures on the impact floors were between 400 and 700°C (750-1,300°F): significantly lower than those associated with typical “fully developed” office fires. However, says Matthys Levy, “By the time the temperature inside the buildings reached 400 degrees, the steel would have lost approximately 50% of its strength. Eventually, gravity took over and the towers began to fall.” Then, according to the analysis led by researchers from LZA Technology/Thornton-Tomasetti, “Once collapse initiated in each tower, essentially all of the interior structure of the tower fell straight down with floors pancaking on top of one another. The network of perimeter steel columns and spandrels acted like a chute to funnel the interior contents into the tower footprint.” According to the computer simulations, the damage to the South Tower’s steel core columns was so severe that the tower should have collapsed immediately after the plane hit. Civil engineer John Osteraas says this incorrect result casts doubt upon some of the study’s predictions. The report concludes that the collapse of the South Tower did not cause or contribute to the subsequent collapse of the North Tower, thus supporting Silverstein Properties’ claim that the terrorist attack represented two occurrences, entitling it to two $3.5 billion insurance policy limits. A separate study commissioned by the insurers contradicts this (see October 23, 2002). The Silverstein report apparently does not examine the collapse of WTC Building 7, a 47-story skyscraper that also collapsed on 9/11 (see (5:20 p.m.) September 11, 2001). It has been passed on to the National Institute of Standards and Technology (NIST), which is undertaking its own investigation of the WTC collapses (see August 21, 2002). [New York Times, 9/30/2002; Business Insurance, 10/23/2002; Silverstein Properties, Inc., 10/23/2002 pdf file; Engineering News-Record, 10/25/2002; New York Times, 10/29/2002; Engineering News-Record, 11/4/2002; Real Estate Weekly, 4/30/2003]

Entity Tags: World Trade Center, Silverstein Properties, Thornton-Tomasetti Engineers, Weidlinger Associates, Matthys Levy

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Insulated trusses in the World Trade Center.
Insulated trusses in the World Trade Center. [Source: Gilsanz Murray Steficek]At a press briefing in New York City, the National Institute of Standards and Technology (NIST) releases a 122-page progress report on its investigation into the WTC collapses. NIST began its study in August 2002 (see August 21, 2002). Investigators say they believe that the Port Authority of New York and New Jersey, who built the Twin Towers, failed to carry out vital tests to establish how the buildings would cope with a major fire. They have been unable to find evidence that tests were conducted on the fireproofing material used in the buildings. Their report also states that in 1969, builders directed contractors to coat the WTC floor supports with half an inch of spray-on fireproofing. In 1999, the Port Authority issued guidelines to triple the thickness of the fireproofing, and by 9/11, about 30 floors in the upper areas of the two towers had been upgraded. Almost all the floors in the impact zone of the North Tower had their fireproofing upgraded, while in the South Tower just the 78th floor—the lowest in its impact zone—had been upgraded. As the New York Times states, though, “investigators took great care… to say they were nowhere close to definitively determining how and why the towers collapsed after they were struck by hijacked airliners.” [National Institute of Standards and Technology, 5/2003, pp. 81; National Institute of Standards and Technology, 5/7/2003; Guardian, 5/8/2003; New York Times, 5/8/2003]

Entity Tags: National Institute of Standards and Technology, Port Authority of New York and New Jersey, World Trade Center

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

The National Institute of Standards and Technology (NIST) issues a progress report on its investigation into the World Trade Center collapses. Since 2002, NIST has been investigating the collapses of the Twin Towers and WTC Building 7 (see August 21, 2002). The progress report includes its “working hypothesis” for the collapse of WTC 7. This was a 47-story building, located about 350 feet from the north side of WTC 1, which collapsed completely at around 5:20 in the afternoon of 9/11. The report claims that “fire appears to have played a key role” in the collapse, though it points out, “No fire was observed or reported in the afternoon on floors 1-5, 10, or above Floor 13.” It also says, “there may have been some physical damage on the south side of the building.” NIST summarizes its working hypothesis of the WTC 7 collapse as follows:
bullet “An initial local failure at the lower floors (below Floor 13) of the building due to fire and/or debris induced structural damage of a critical column (the initiating event), which supported a large span floor bay with an area of about 2,000 square feet.”
bullet “Vertical progression of the initial local failure up to the east penthouse, as large floor bays were unable to redistribute the loads, bringing down the interior structure below the east penthouse.”
bullet “Horizontal progression of the failure across the lower floors… triggered by damage due to the vertical failure, resulting in the disproportionate collapse of the entire structure.”
NIST claims this hypothesis “is consistent with all evidence currently held by NIST, including photographs and videos, eyewitness accounts and emergency communication records,” but says it “will be revised and updated as results of ongoing, more comprehensive analyses become available.” [National Institute of Standards and Technology, 6/2004, pp. L1, L3, L17, L34, L38, L51-L52; National Institute of Standards and Technology, 6/18/2004] NIST will release its final reports on the collapses of the Twin Towers in October 2005 (see October 26, 2005). As of mid-2007, it has yet to release a final report on the collapse of WTC 7. In early 2006, Dr. S. Shyam Sunder, who is the lead investigator for NIST’s WTC investigation, will admit, “truthfully, I don’t really know” what caused WTC 7 to collapse. He will add, “We’ve had trouble getting a handle on building no. 7” (see March 20, 2006). [New York Magazine, 3/20/2006] An earlier report on the WTC collapses, released by the Federal Emergency Management Agency (FEMA) in May 2002, had been inconclusive on what caused WTC 7 to collapse, and stated that “Further research, investigation, and analyses” were necessary (see May 1, 2002). [Federal Emergency Management Agency, 5/1/2002, pp. 5-31]

Entity Tags: World Trade Center, National Institute of Standards and Technology

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Shyam Sunder.Shyam Sunder. [Source: NIST]The National Institute of Standards and Technology (NIST) releases nearly 500 pages of documents, detailing the latest findings of its investigation of the WTC collapses on 9/11. These include its hypotheses for the collapse sequences of each of the Twin Towers; details of their analysis of interviews with nearly 1,200 building occupants, emergency responders, and victims’ relatives; and information from their analysis of the emergency response and evacuation procedures. Their investigation into the collapses is based upon an analysis of thousands of photos and videos, examination of many of the elements used to construct the towers, and computer-enhanced modeling of the plane impacts and the spreading of the fires. Their hypothesis is that the towers collapsed ultimately due to the fires they suffered: As the fires burned, the buildings’ steel core columns buckled and shortened. This shifted more load to the buildings’ perimeter columns, which were already affected by the heat of the fires, and caused them to give way under the increased stress. Investigators have conducted a test with a reconstructed section of the WTC floor, and found that the original fireproofing was sufficient to meet the New York City building code. They say that had a typical office fire occurred in the towers, without the structural damage and the loss of some fireproofing caused by the plane impacts, it is likely the buildings would have remained standing. Lead investigator Dr. Shyam Sunder says, “The buildings performed as they should have in the airplane impact and extreme fires to which they were subjected. There is nothing there that stands out as abnormal.” NIST’s theories of why the WTC buildings collapsed conflict with an earlier investigation by FEMA, which claimed the collapse of the North Tower had begun in its core, rather than its perimeter columns (see May 1, 2002). [National Institute of Standards and Technology, 10/19/2004; New York Times, 10/20/2004]

Entity Tags: Shyam Sunder, National Institute of Standards and Technology, World Trade Center

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Based upon its three-year investigation of the WTC collapses, the National Institute of Standards and Technology (NIST) calls for changes in the planning, construction, and operation of skyscrapers. NIST releases 43 draft reports, totaling about 10,000 pages, for public comments. These include 25 pages of recommendations, intended to learn from 9/11 and make building occupants and emergency responders safer in any future disasters. NIST’s inquiry has been conducted by more than 200 technical experts and contractors, and had two main parts: to look at the causes of the collapses and to identify weaknesses in building codes. Their recommendations include specific improvements to building standards, codes and practices; changes to evacuation and emergency response procedures; and research to help prevent future building failures. NIST does not have the authority to change building codes, but hopes to influence the policies of local authorities. The cost of implementing their recommended changes would add an estimated extra 2 to 5 percent to the development costs of buildings. Some are critical of their recommendations. Structural engineer Jon Magnusson, whose firm is the descendant of the company that designed the Twin Towers, says, “They are leading the public down the wrong path. They are saying we are going to fix the codes in order to deal with Sept. 11th. The physics say that you can’t do that.” [New York Times, 6/22/2005; National Institute of Standards and Technology, 6/23/2005; Associated Press, 6/24/2005] The New York Times points out that between 1989 and 1999, only five civilians had been killed in some 6,900 reported high-rise office building fires within the US. [New York Times, 6/24/2005] NIST will release its final report on the Twin Towers collapses four months later (see October 26, 2005).

Entity Tags: National Institute of Standards and Technology, World Trade Center, Jon Magnusson

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Both towers of the World Trade Center tilted to one side before beginning to fall on 9/11 (see 9:59 a.m. September 11, 2001 and 10:28 a.m. September 11, 2001). The National Institute of Standards and Technology, which investigated the collapses (see August 21, 2002), states that the South Tower, which was hit on its south side, tilted about 7-8 degrees to the east and 3-4 degrees to the south, and the North Tower, which was hit on its north side, tilted about 8 degrees to the south, before starting to fall. [National Institute of Standards and Technology, 9/2005, pp. 300, 308 pdf file] However, these findings are criticized by Canadian scientist Frank Greening. After examining photo and video evidence, Greening says that the South Tower tilted by no more than two degrees and the North Tower by no more than three degrees before collapse initiation. Greening also says that the tilt angles NIST gives cannot correspond to the downward movement of the towers’ walls NIST claims before they started to fall, and points out that the tilt angles NIST uses are inconsistent throughout its reports. Though Greening agrees with NIST that the towers were destroyed by the plane impacts and fire damage, he concludes that its computer model is “highly inaccurate and therefore of no value in explaining the demise of the Twin Towers.” [Greening, 11/2005 pdf file] Greening is a leading figure in the post-9/11 dispute over why the WTC collapsed and publishes a series of papers dealing with various aspects of the Twin Towers’ collapse. For example, a CBC documentary uses Greening for analysis of the WTC’s fall. [Canadian Broadcasting Corporation, 8/25/2005]

Entity Tags: World Trade Center, Frank Greening, National Institute of Standards and Technology

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

The 43 NIST reports ran to over 10,000 pages.The 43 NIST reports ran to over 10,000 pages. [Source: NIST]The National Institute of Standards and Technology (NIST) issues the final report of its three-year, $16 million study into the WTC collapses on 9/11. NIST has produced over 10,000 pages of findings, and its report includes 30 recommendations for improving building safety, such as having wider stairwells and structurally hardened elevators for use in emergencies. The recommendations are mostly the same as those outlined in an earlier draft of the report (see June 23, 2005). [Engineering News-Record, 10/27/2005; New York Times, 10/27/2005] NIST has made some amendments and clarifications, though, based upon nearly 500 comments received during a six-week public review period. [National Institute of Standards and Technology, 10/26/2005] NIST’s theory about what caused the Twin Towers to collapse remains the same as that described in its previously released findings (see October 19, 2004). However, the NIST’s account only examines events up to the initiation of each collapse; the investigation “does not actually include the structural behavior of the tower after the conditions for collapse initiation were reached and collapse became inevitable.” [National Institute of Standards and Technology, 9/2005, pp. 82] NIST makes no mention of molten metal found at the collapse site in the weeks and months after 9/11, which has been described in numerous reports (see September 12, 2001-February 2002). The “NIST found no corroborating evidence for alternative hypotheses suggesting that the WTC towers were brought down by controlled demolition using explosives planted prior to September 11, 2001.” [National Institute of Standards and Technology, 9/2005, pp. 146] Members of Congress are critical of NIST’s recommendations, saying they are not detailed enough, or adequately documented, to be rapidly incorporated into standard building code publications. [New York Times, 10/27/2005] According to Glenn Corbett, a technical adviser to NIST and fire science professor at John Jay College, NIST is not aggressive enough to carry out major forensic investigations. He says, “Instead of a gumshoe inquiry that left no stone unturned, I believe the investigations were treated more like research projects in which they waited for information to flow to them.” [Associated Press, 10/26/2005; US Congress, 10/26/2005 pdf file] NIST will release its final report on the collapse of Building 7 of the WTC separately, at a later date. [National Institute of Standards and Technology, 9/2005, pp. xiii]

Entity Tags: World Trade Center, Glenn Corbett, National Institute of Standards and Technology

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

In a reply to criticisms of its World Trade Center investigation, the National Institute of Standards and Technology (NIST) admits that it is unable to fully explain the total collapse of the Twin Towers on 9/11. NIST’s letter is a response to a “request for correction” letter sent to it five months earlier by Bob McIlvaine and Bill Doyle, who both lost family members on 9/11, along with scientists Kevin Ryan and Steven E. Jones, architect Richard Gage, and the group Scholars for 9/11 Truth and Justice. This letter made several assertions about NIST’s final reports of its WTC investigation, and suggested they had violated the Data Quality Act and NIST’s information quality standards. NIST’s reply denies the requests for corrections. However, it also mentions, “[W]e are unable to provide a full explanation of the total collapse” of the World Trade Center. [National Institute of Standards and Technology, 9/27/2007 pdf file] In its final report on the Twin Towers collapses, released in October 2005, NIST admitted that its investigation did “not actually include the structural behavior of the tower after the conditions for collapse initiation were reached and collapse became inevitable” (see October 26, 2005). [National Institute of Standards and Technology, 9/2005, pp. 82]

Entity Tags: National Institute of Standards and Technology, World Trade Center

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

The National Institute of Standards and Technology (NIST) publishes a fact sheet responding to 14 “frequently asked questions” about its investigation into the collapse of the Twin Towers on September 11. Some of the key questions and answers are as follows:
bullet Regarding the question, “Why was the collapse of WTC 1 and 2 not arrested by the intact structure below the floors where columns first began to buckle?” NIST replies, “The vertical capacity of the connections supporting an intact floor below the level of collapse was adequate to carry the load of 11 additional floors if the load was applied gradually and 6 additional floors if the load was applied suddenly (as was the case).” As the number of floors above the points where the collapses initiated exceeded six (12 in the case of the North Tower, 29 for the South), NIST says, “[T]he floors below the level of collapse initiation were unable to resist the suddenly applied gravitational load from the upper floors of the buildings.”
bullet In answer to the question of “Why was physical evidence not collected immediately following the collapse of the WTC towers,” NIST says, “In the initial days and weeks following the WTC disaster, the emphasis was on rescue and later on recovery, necessitating the removal of steel and disturbing the collapse site.” It adds, “NIST did not receive the legal authority to collect and preserve physical evidence from a disaster/failure site until the National Construction Safety Team Act became law in October 2002.” The decision to rapidly scrap the remaining steel from the WTC was made shortly after 9/11 (see Shortly After September 11, 2001), but the destruction of this steel was strongly protested by some within the engineering and firefighting communities (see December 25, 2001 and January 4, 2002).
bullet In response to a question about why it did not use its subpoena authority during its investigation, NIST states that its “experience during the investigation was that it was able to obtain all essential documentary and visual evidence without the need to invoke subpoena authority.”
bullet In answer to the question, “Why didn’t NIST fully model the collapse initiation and propagation of WTC towers?” NIST says, “Once the collapse had begun, the propagation of the collapse was readily explained without the same complexity of modeling” as was used to determine the sequence of events leading up to the collapse initiation.
bullet During its investigation, NIST had selected several variables for its computer simulations, and then experimented with different possible values (see (October 2002-October 2005)). But it has been asked: “Why didn’t NIST consider the ‘base’ and ‘less severe’ cases throughout its analysis of the WTC towers? What was the technical basis for selecting only the ‘more severe’ case for its analyses?” Its answer is that, “Of the three [possible values], the more severe case resulted in the closest agreement with the visual and physical evidence.” [National Institute of Standards and Technology, 12/14/2007]
NIST published its final report on the Twin Towers collapse in October 2005 (see October 26, 2005). It released an earlier fact sheet answering previous “frequently asked questions” in August 2006 (see August 30, 2006). [National Institute of Standards and Technology, 8/30/2006]

Entity Tags: National Institute of Standards and Technology

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

NIST lead investigator Shyam Sunder answering questions about NIST’s three-year study of the collapse of WTC 7.NIST lead investigator Shyam Sunder answering questions about NIST’s three-year study of the collapse of WTC 7. [Source: Don Berkemeyer / National Institute of Standards and Technology]The National Institute of Standards and Technology (NIST) announces the findings of its study of the collapse of World Trade Center Building 7, and says the 47-story tower fell late in the afternoon of 9/11 primarily due to fires. [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 8/21/2008] NIST releases its findings as part of a 915-page report, which is the result of three years’ work by over 50 federal investigators and a dozen contractors (see August 21, 2008). [New York Times, 8/21/2008]
Collapse Is 'No Longer a Mystery' - In a news conference at NIST’s headquarters in Gaithersburg, Maryland, lead investigator Shyam Sunder admits: “[W]e 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.” But, he says, “[T]he reason for the collapse of World Trade Center 7 is no longer a mystery.” [National Institute of Standards and Technology, 8/21/2008; New York Times, 8/21/2008]
'New Phenomenon' Caused Collapse - Sunder says the “critical factor” that initiated the collapse was “thermal expansion of long-span floor systems located in the east side of the building,” and adds that NIST’s study “has identified thermal expansion as a new phenomenon that can cause structural collapse. For the first time we have shown that fire can induce a progressive collapse.”
Collapse Sequence - Sunder describes the sequence of events NIST believes led to the collapse of WTC 7. He says debris from the collapse of the north WTC tower “started fires on at least 10 floors of the building. The fires burned out of control on six of these 10 floors for about seven hours. The city water main had been cut by the collapse of the two WTC towers, so the sprinklers in Building 7 did not function for much of the bottom half of the building.” He continues: “Fires on floors 7 through 9 and 11 through 13 were particularly severe.… Eventually, a girder on floor 13 lost its connection to a critical interior column.” Floor 13 collapsed, beginning a cascade of floor failures down to the fifth floor. “With the support of these floors gone, column 79 buckled, which initiated the fire-induced progressive collapse of the building.… This in turn caused the failure of nearby columns 80 and 81 and floor failures up to the roof line.… As the roof line begins to fall adjacent columns buckle as well. In quick succession, the remaining interior columns failed from east to west across WTC 7, until the entire core began moving downward. Finally, the remaining outer shell or fa├žade of the building fell.”
NIST Created 'Virtual WTC 7' Model - Sunder says that NIST reached its conclusions about the collapse “by reconstructing the entire building, beam by beam, column by column, connection by connection into a computer model, a virtual WTC 7 building. We then filled that virtual building with as much detail as possible about exactly what types of furnishings were on each floor. Then we set fire to those virtual offices on the floors where video and other visual evidence told us the fires burned.” The investigators “used a well-validated computer program developed at NIST, for studying the growth and spread of fires, to calculate temperatures throughout the building.… And we used well-established data on the properties of structural steel, the sprayed fire resistive material or fireproofing, and other building materials to determine how those temperatures affected the structure.”
Explosives Not Used - Sunder says that the investigators “did not find any evidence that explosives were used to bring the building down” (see August 21, 2008), nor was the collapse “due to fires from the substantial amount of diesel fuel stored in the building” (see August 21, 2008). NIST commenced its investigation of the WTC collapses in 2002 (see August 21, 2002) and issued its findings on the collapses of the Twin Towers in October 2005 (see October 26, 2005). Since then it has been focused on WTC 7. [Government Computer News, 8/21/2008; National Institute of Standards and Technology, 8/21/2008]
Final Report to Be Released - After suggestions are made by members of the public in response to its current report, NIST will release a finished version of the same report in November 2008, thereby completing its WTC investigation (see November 20, 2008). [National Institute of Standards and Technology, 11/20/2008]

Entity Tags: World Trade Center, National Institute of Standards and Technology, Shyam Sunder

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

NIST’s ‘Final Report on the Collapse of World Trade Center Building 7.’NIST’s ‘Final Report on the Collapse of World Trade Center Building 7.’ [Source: National Institute of Standards and Technology.]The National Institute of Standards and Technology (NIST) releases the final report of its three-year investigation of the collapse of World Trade Center Building 7, the 47-story skyscraper which collapsed late in the afternoon of 9/11 (see (5:20 p.m.) September 11, 2001). This is the completed version of the report, and comes three months after a draft version was released for public comment (see August 21, 2008). NIST states that the new report “is strengthened by clarifications and supplemental text suggested by organizations and individuals worldwide in response to the draft WTC 7 report.” NIST conducted an additional computer analysis in response to comments from the building community, and made several minor amendments to the report. But, it says, “the revisions did not alter the investigation team’s major findings and recommendations, which include identification of fire as the primary cause for the building’s failure.” With the release of this report, NIST has completed its six-year investigation of the World Trade Center collapses, which it commenced in August 2002 (see August 21, 2002). The final report of its investigation of the Twin Towers’ collapses was published in October 2005 (see October 26, 2005). [National Institute of Standards and Technology, 11/20/2008; Occupational Health and Safety, 11/25/2008]

Entity Tags: World Trade Center, National Institute of Standards and Technology

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

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