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Context of 'March 12, 2002: Structural Engineer Criticizes Decision to Destroy WTC Steel'

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Leslie Robertson.Leslie Robertson. [Source: Publicity photo]Leslie Robertson, one of the two original structural engineers for the World Trade Center, is asked at a conference in Frankfurt, Germany what he had done to protect the Twin Towers from terrorist attacks. He replies, “I designed it for a 707 to smash into it,” though does not elaborate further. [Chicago Tribune, 9/12/2001; Knight Ridder, 9/12/2001] The Twin Towers were in fact the first structures outside the military and nuclear industries designed to resist the impact of a jet airplane. [Robertson, 3/2002; Federal Emergency Management Agency, 5/1/2002, pp. 1-17] The Boeing 707 was the largest in use when the towers were designed. Robertson conducted a study in late 1964, to calculate the effect of a 707 weighing 263,000 pounds and traveling at 180 mph crashing into one of the towers. He concluded that the tower would remain standing. However, no official report of his study has ever surfaced publicly. [Glanz and Lipton, 2004, pp. 138-139, 366] A previous analysis, carried out early in 1964, calculated that the towers would handle the impact of a 707 traveling at 600 mph without collapsing (see February 27, 1993). In 2002, though, Robertson will write, “To the best of our knowledge, little was known about the effects of a fire from such an aircraft, and no designs were prepared for that circumstance.” [Robertson, 3/2002] The planes that hit the WTC on 9/11 are 767s, which are almost 20 percent heavier than 707s. [Scientific American, 10/9/2001; New Yorker, 11/19/2001]

Entity Tags: Leslie Robertson, World Trade Center

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Dr. Abolhassan Astaneh-Asl examines steel from the World Trade Center.Dr. Abolhassan Astaneh-Asl examines steel from the World Trade Center. [Source: University of California, Berkeley]An engineer investigating the remains of the World Trade Center sees melted girders and other evidence that the towers experienced extreme temperatures on 9/11. Dr. Abolhassan Astaneh-Asl is a professor of civil and environmental engineering at the University of California, Berkeley. He specializes in studying structural damage done by earthquakes and terrorist bombings. [Chronicle of Higher Education, 12/7/2001; CBS News, 3/11/2002] He arrives in New York on September 19 to conduct a two-week scientific reconnaissance of the collapsed towers, hoping to gain an understanding of how they had come down. His project is one of eight financed by the National Science Foundation to study the WTC disaster. [New York Times, 10/2/2001; Berkeleyan, 10/3/2001; US Congress. House. Committee on Science, 3/6/2002] He examines numerous pieces of steel taken from Ground Zero. [Chronicle of Higher Education, 12/7/2001] Astaneh-Asl will describe the WTC as “the best-designed building I have ever seen.” [San Francisco Chronicle, 10/22/2001] Yet he notices unusual warping and other damage in its remaining steel:
bullet At a recycling center in New Jersey, he sees 10-ton steel beams from the towers that look “like giant sticks of twisted licorice.” [Chronicle of Higher Education, 12/7/2001] He shows the San Francisco Chronicle a “banana-shaped, rust-colored piece of steel” that has “twisted like toffee during the terrorist attack.” [San Francisco Chronicle, 10/22/2001]
bullet He later recalls, “I saw melting of girders in [the] World Trade Center.” [PBS, 5/10/2007]
bullet He notes that steel has bent at several connection points that had joined the floors of the WTC to the vertical columns. He describes the connections as being smoothly warped, saying, “If you remember the Salvador Dali paintings with the clocks that are kind of melted—it’s kind of like that.” He adds, “That could only happen if you get steel yellow hot or white hot—perhaps around 2,000 degrees.” [Chronicle of Higher Education, 12/7/2001]
bullet Astaneh-Asl says that steel flanges have been reduced “from an inch thick to paper thin.” [Berkeleyan, 10/3/2001]
bullet He finds a foot-long twisted shard of steel that is “like a piece of bread, but it was high-strength steel.” He comments, “I haven’t seen anything like this [before].” [Berkeley Daily Planet, 10/20/2001]
bullet He finds “severely scorched [steel] members from 40 or so floors below the points of impact [by the planes].” He believes this is the result of the planes having destroyed the elevator walls, thereby allowing burning jet fuel to pour down into the building, igniting fires hundreds of feet below the impact floors. [CBS News, 3/12/2002]
bullet He says that, in some places, the fireproofing used to protect the WTC steel has “melted into a glassy residue.” [New York Times, 10/2/2001]
bullet Astaneh-Asl sees a charred I-beam from WTC Building 7, which collapsed late in the afternoon of 9/11. “The beam, so named because its cross-section looks like a capital I, had clearly endured searing temperatures. Parts of the flat top of the I, once five-eighths of an inch thick, had vaporized.” [New York Times, 10/2/2001]
Other individuals will report seeing molten metal in the remains of the World Trade Center in the weeks and months after 9/11 (see September 12, 2001-February 2002), and data collected by NASA reveals dozens of “hot spots” (some over 1,300 degrees Fahrenheit) at Ground Zero (see September 16-23, 2001). But Thomas Eagar—an engineering professor at the Massachusetts Institute of Technology—later comments that the “temperature of the fire at the WTC [on 9/11] was not unusual, and it was most definitely not capable of melting steel.” [Eagar and Musso, 12/2001] Yet Astaneh-Asl will later put forward the “tentative” conclusion, “The collapse of the [Twin Towers] was most likely due to the intense fire initiated by the jet fuel of the planes and continued due to burning of the building contents.” [Astaneh-Asl, 11/30/2003 pdf file] Astaneh-Asl is a member of the team assembled by the American Society of Civil Engineers to investigate the World Trade Center site after 9/11 (see September 12, 2001), though he will resign from this because he disagrees with its decision to keep findings secret until the initial inquiry has been completed. [New York Times, 10/2/2001; Associated Press, 9/6/2002]

Entity Tags: World Trade Center, Thomas Eagar, Abolhassan Astaneh-Asl

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

A structural engineer who was a member of the team assembled by the American Society of Civil Engineers to investigate the World Trade Center site after 9/11 complains about the decision to rapidly destroy the remaining structural steel from the collapsed WTC buildings. Dr. Abolhassan Astaneh-Asl is a professor of civil and environmental engineering at the University of California at Berkeley, and specializes in studying structural damage done by earthquakes and terrorist bombings. [Chronicle of Higher Education, 12/7/2001; CBS News, 3/11/2002; Associated Press, 9/6/2002] He had come to New York a week after 9/11 to examine the collapsed towers, hoping to gain an understanding of how they had come down (see September 19-October 2001). [New York Times, 10/2/2001; US Congress. House. Committee on Science, 3/6/2002] However, New York City officials had decided early on to quickly transport the remaining structural steel to scrap yards, to be shipped abroad and melted down for reuse (see Shortly After September 11, 2001). As CBS News now reports, “As a result, Astaneh has almost certainly missed seeing crucial pieces before they were cut up and sent overseas.” Astaneh-Asl complains: “When there is a car accident and two people are killed, you keep the car until the trial is over. If a plane crashes, not only do you keep the plane, but you assemble all the pieces, take it to a hangar, and put it together. That’s only for 200, 300 people, when they die. In this case you had 3,000 people dead.” He says: “My wish was that we had spent whatever it takes, maybe $50 million, $100 million, and maybe two years, get all this steel, carry it to a lot. Instead of recycling it, put it horizontally, and assemble it. You have maybe 200 engineers, not just myself running around trying to figure out what’s going on. After all, this is a crime scene and you have to figure out exactly what happened for this crime, and learn from it.” However, he adds, “My wish is not what happens.” [CBS News, 3/12/2002] Astaneh-Asl previously told the New York Times that the scrap steel from the WTC was “worth only a few million dollars, a tiny fraction of the billions of dollars the cleanup will cost.” Yet the knowledge that could be gained from it “could save lives in a future disaster.” [New York Times, 10/2/2001]

Entity Tags: World Trade Center, Abolhassan Astaneh-Asl

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


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