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Context of '(Shortly Before 8:46 a.m.) September 11, 2001: Boston Center Controller Predicts Flight 11 Will Crash into WTC'

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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

One of the key variables in the computer simulations used by the National Institute of Standards and Technology (NIST) (see (October 2002-October 2005)) to explain the WTC collapses is the speed of the aircraft that hit the towers. However, there is no consensus on how fast the planes were traveling. The first estimate was contained in an initial research paper by engineers Zdenek Bazant and Yong Zhou, who stated that the planes were traveling at 342 miles per hour. [Bazant and Zhou, 1/2002 pdf file] However, the Federal Emergency Management Agency (FEMA) and American Society of Civil Engineers (ASCE) report said that the plane that hit the North Tower was traveling at 470 miles per hour, whereas the plane that hit the South Tower was traveling at 590 miles per hour (see May 1, 2002). [Federal Emergency Management Agency, 5/1/2002, pp. 31] NIST initially estimates speeds of 435 miles per hour for the plane that hit the North Tower and 497 miles per hour for the plane that hit the South Tower. These estimates closely match figures produced by the Massachusetts Institute of Technology, which finds speeds of 429 miles per hour and 503 miles per hour for the two planes. However, NIST is dissatisfied with these results and does a second study, which finds speeds of 466 and 545 miles per hour. It then uses speeds of 472 and 570 miles per hour in its severe case model, on which its final report is based. In this model, the simulation of the planes traveling faster means greater damage to the towers’ structure, making them more unstable. [Kausel, 5/2002 pdf file; National Institute of Standards & Technology, 9/2005, pp. 152-165 pdf file; National Institute of Standards and Technology, 9/2005, pp. 109]

Entity Tags: Zdenek Bazant, National Institute of Standards and Technology, World Trade Center, Yong Zhou, Massachusetts Institute of Technology, American Society of Civil Engineers, Federal Emergency Management Agency

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

At the end of a two-day meeting to discuss the progress of their investigation of the WTC collapses on 9/11, National Institute of Standards and Technology (NIST) investigators say that early tests on steel beams recovered from the World Trade Center showed they met or were stronger than design requirements. NIST has collected 236 pieces of steel from the wreckage of the towers. Tests have found that the steel beams exceeded requirements to bear 36,000 pounds per square inch, and were often capable of bearing around 42,000 pounds per square inch. Lead investigator Shyam Sunder says that if further testing corroborates these findings, this will rule out weak steel as a factor in the collapses. [National Institute of Standards and Technology, 8/26/2003; Associated Press, 8/28/2003] The final report of the NIST investigation, released in 2005, will corroborate this finding: “Overall, approximately 87 percent of all perimeter and core column steel tested exceeded the required minimum yield strengths specified in design documents. Test data for the remaining samples were below specifications, but were within the expected variability and did not affect the safety of the towers on September 11, 2001.” It also will point out: “Of the more than 170 areas examined on 16 perimeter column panels, only three columns had evidence that the steel reached temperatures above 250°C.… Only two core column specimens had sufficient paint remaining to make such an analysis, and their temperatures did not reach 250°C.… Using metallographic analysis, NIST determined that there was no evidence that any of the samples had reached temperatures above 600 °C.” [National Institute of Standards and Technology, 9/2005, pp. 89-90]

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

The National Institute of Standards and Technology (NIST), which is conducting an investigation into the WTC collapses on 9/11, releases three new reports. Investigators say that the Twin Towers would probably have remained standing if the fireproofing material that surrounded the buildings’ structural steel had not been stripped away when the planes hit. Their report states that “[t]he jet fuel, which ignited the fires, was mostly consumed within the first few minutes after impact. The fires that burned for almost the entire time that the buildings remained standing were due mainly to burning building contents and, to a lesser extent, aircraft contents, not jet fuel.” However, they claim, without the loss of fireproofing during the planes’ impacts, the heat from the fires would have been insufficient to cause the buildings to collapse. They say that although the architects had in 1964 tested the impact of a Boeing 707 airplane crashing into the 80th floor of one of the towers, they never envisioned the intense fires that ensued. NIST also reports that the time taken by survivors from the North Tower to descend a flight of stairs was about double the slowest evacuation speed estimated in a standard fire engineering text. They state: “approximately 87 percent of the WTC tower occupants, including more than 99 percent below the floors of impact, were able to evacuate successfully.” However, they say, if each tower had been full when they were hit, as many as 14,000 people could have died. [National Institute of Standards and Technology, 4/5/2005; Associated Press, 4/5/2005; New York Times, 4/5/2005; Associated Press, 4/6/2005]

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

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

National Institute of Standards and Technology (NIST) releases a 12-page appendix to its final reports on the WTC collapses (see October 26, 2005) detailing tests it conducted on samples of the type of fireproofing used in the WTC. An earlier NIST report had concluded that loss of fireproofing was a major factor in the collapses (see April 5, 2005). The appendix was not included in earlier drafts of the report (see June 23, 2005) [National Institute of Standards and Technology, 6/23/2005 pdf file; National Institute of Standards & Technology, 9/2005, pp. 263-274 pdf file; National Institute of Standards and Technology, 9/2005, pp. 149] NIST conducted a series of fifteen tests. In the tests projectiles were fired at fireproofing mounted on 12 inch x 12 inch plates, and steel bars with a one inch diameter. The fireproofing used in the tests was Blazeshield DC/F, one of the two grades of fireproofing used on the impact floors. In thirteen of the tests the projectiles were buckshot, which was fired at the steel samples from a modified shotgun at a distance of 29.5 ft. The other two tests used steel bolts and hexagon nuts, fired with less velocity and at closer range. According to NIST, “The test results support the assumption that, within the debris field created by the aircraft impact into WTC 1 and WTC 2, the SFRM [i.e., fireproofing] used for thermal insulation of structural members was damaged and dislodged.” [National Institute of Standards & Technology, 9/2005, pp. 83, 263-274 pdf file]

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

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Former 9/11 Commission co-chair Lee Hamilton.Former 9/11 Commission co-chair Lee Hamilton. [Source: CBC]Lee Hamilton, the former co-chair of the 9/11 Commission, gives a wide-ranging interview to the CBC about Without Precedent, a book he recently co-authored about his time on the 9/11 Commission (see August 15, 2006). In the interview he discusses the various “conspiracy theories” surrounding the events of 9/11. The interviewer, Evan Solomon, mentions to him a recent Zogby poll (see May 17, 2006) that found that 42% of Americans agreed that “the US government, and its 9/11 Commission, concealed or refused to investigate critical evidence that contradicts the official explanation of September 11th.” Hamilton calls this lack of trust in the Commission’s report “dispiriting,” but attacks the “conspiracy theory people,” saying, “when they make an assertion they do it often on very flimsy evidence.” He addresses some of the various “conspiracy theories” that have been put forward about 9/11:
bullet In order to contradict the allegation that the Twin Towers were brought down deliberately with pre-planted explosives, Hamilton says the WTC collapsed (see 8:57 a.m. September 11, 2001) because “the super-heated jet fuel melted the steel super-structure of these buildings and caused their collapse.” He adds, “There’s a powerful lot of evidence to sustain that point of view, including the pictures of the airplanes flying into the building.”
bullet With regard to the collapse of WTC Building 7 (see (5:20 p.m.) September 11, 2001), which some people claim was also caused by explosives, he argues, “[W]e believe that it was the aftershocks of these two huge buildings in the very near vicinity collapsing. And in the Building 7 case, we think that it was a case of flames setting off a fuel container, which started the fire in Building 7, and that was our theory on Building 7.” However, the interviewer points out that the 9/11 Commission’s final report does not actually mention the collapse of Building 7, and Hamilton says he does not recall whether the Commission made a specific decision to leave it out.
bullet In reply to a question about why the debris of Building 7 were moved quickly from the scene without a thorough investigation, even though nobody died in Building 7 and there was no need for rescue operations there, Hamilton responds, “You can’t answer every question when you conduct an investigation.”
bullet When asked whether Saeed Sheikh sent Mohamed Atta $100,000 for the 9/11 plot (see Early August 2001 and Summer 2001 and before), Hamilton replies, “I don’t know anything about it.” When the interviewer presses him about whether the Commission investigated a possible Pakistani Secret Service (ISI) connection to the attacks, Hamilton replies, “They may have; I do not recall us writing anything about it in the report. We may have but I don’t recall it.”
bullet Asked about Secretary of Transportation Norman Mineta’s claim that Vice President Dick Cheney was in the presidential bunker beneath the White House at 9:20 a.m. on 9/11 (see (Between 9:20 a.m. and 9:27 a.m.) September 11, 2001), almost 40 minutes earlier than the Commission claimed he had arrived there, Hamilton replies, “I do not recall.” When pressed, he expands, “Well, we think that Vice President Cheney entered the bunker shortly before 10 o’clock. And there is a gap of several minutes there, where we do not really know what the Vice President really did. There is the famous phone call between the President and the Vice President. We could find no documentary evidence of that phone call.”
bullet When the interviewer points out that Richard Clarke’s account conflicts with the Commission’s over what time authorization was received from Dick Cheney to shoot down Flight 93 (see (Between 9:45 a.m. and 9:56 a.m.) September 11, 2001 and (Between 10:00 a.m. and 10:15 a.m.) September 11, 2001), Hamilton retorts, “Look, you’ve obviously gone through the report with a fine-toothed comb, you’re raising a lot of questions—I can do the same thing.”
The interviewer also asks Hamilton whether he has any unanswered questions of his own about 9/11. Hamilton’s response is: “I could never figure out why these 19 fellas did what they did. We looked into their backgrounds. In one or two cases, they were apparently happy, well-adjusted, not particularly religious - in one case quite well-to-do, had a girlfriend. We just couldn’t figure out why he did it. I still don’t know.” [Canadian Broadcasting Corporation, 8/21/2006]

Entity Tags: Saeed Sheikh, World Trade Center, Richard (“Dick”) Cheney, Pakistan Directorate for Inter-Services Intelligence, Lee Hamilton, 9/11 Commission, Richard A. Clarke, Mohamed Atta, Norman Mineta

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

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