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9/11 building brought down by fire, not explosives, report says
By Eric Lipton The New York Times
Thursday, August 21, 2008
Fires in the 47-story office tower at the edge of the World Trade Center site undermined floor beams and critical structural columns, federal investigators concluded Thursday, as they attempted to curb still-rampant speculation that explosives or fuel fires had been responsible for the collapse of the building on Sept. 11, 2001.
The long-delayed report by engineers at the National Institute of Standards and Technology in suburban Washington is intended to solve one of the lingering questions about the 2001 attacks: Why did the building at 7 World Trade Center fall, if it was not hit by an airplane?
"Heating of floor beams and girders caused a critical support column to fail," said Shyam Sunder, the lead investigator. "Video and photographic evidence, combined with detailed computer simulations, show that neither explosives nor fuel oils played a role."
No one died when 7 World Trade Center fell, nearly seven hours after the center's twin towers collapsed. But the fall of the adjacent tower - once home to branch offices of the CIA, the Secret Service and the emergency operations center of the New York City mayor - is cited in hundreds of books and Internet sites as perhaps the most compelling evidence that an insider secretly planted explosives, intentionally destroying the tower.
It is the first skyscraper in modern times to collapse primarily as a result of a fire.
Mainstream engineers and government officials have rejected the speculation as ridiculous. But national polls have shown that perhaps as many as one in seven Americans believes that the destruction of the World Trade Center towers was an inside job.
The investigators determined that debris from the falling twin towers ignited fires on at least 10 floors at 7 World Trade Center, which was about 400 feet, or 120 meters, north of where the two tallest buildings in the city once stood. The blazes burned out of control for six hours. The city fire department, devastated by the collapse of the twin towers, abandoned its efforts to extinguish the fire and the sprinkler system was incapacitated.
The heat from these fires, the investigators said, caused the beams on the lower floors of the east side of the tower to expand, ultimately causing a girder on the 13th floor to disconnect from a critical interior column that supported the building's long floor spans. Once the 13th floor gave way, a cascade of floor failures led to the overall collapse of the tower.
Skeptics have questioned whether explosives were planted at 7 World Trade Center, as well as the twin towers and the Pentagon, as the Bush administration was seeking a justification to invade Iraq and Afghanistan. What started as a small number of such conspiracy theorists has ballooned into a movement of sorts, largely fed by Internet sites that promote the theories.
"Seven World Trade Center is one of the key points of evidence, one of the smoking guns," said Richard Gage, a California architect who is leader a group called Architects and Engineers for 9/11 Truth. "There have been much hotter, longer lasting and larger fires in skyscrapers that have not fallen down."
The engineers also examined whether diesel fuel tanks in the building - to power the mayor's emergency operations center and other government offices - might have been a fuel source that caused the collapse. The investigators determined, partly on the basis of computer models and videos of smoke coming from the tower, that the heat generated from any fuel-fed fires would not have been enough to cause the collapse.
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