The world may never know exactly what happened or the exact sequence of events that took place at the World Trade Center on Sept. 11, 2001. But in the end, the collapse of the center's 110-story Twin Towers was caused by the terrific impacts they sustained by two hijacked jet airliners. That is the observation of one member of the task force that is charged with studying the collapse of the World Trade Center's Twin Towers.
Speaking before structural engineers, fabricators and erectors at the North American Steel Construction Conference in Seattle, Wednesday, April 24, Jon Magnusson, chairman of the local structural engineering firm Skilling, Ward, Magnusson, Barkshire, and a member of the American Society of Civil Engineers (ASCE)/Federal Emergency Management Agency (FEMA) World Trade Center building performance assessment team assembled to study the collapse, said that heavier-duty design of buildings and tougher fire codes are useless unless control of airplanes like the 767s that struck the Twin Towers are secured.
'We can't let airplanes like [those that attacked the Twin Towers] hit our buildings,' said Magnusson, whose firm, then known as Skilling, Halle, Christiansen, Robertson, provided the structural engineering for the Twin Towers in 1972 and 1973. Former partner Les Robertson led that effort.
Other members of the ASCE/FEMA task force, including Chairman W. Eugene Corley, are to testify about the task force's findings today on Capitol Hill in Washington, D.C., before the House Committee on Science.
Stronger designs and more stringent fire codes won't matter if airplane security is not greatly improved, said Magnusson. 'Design load condition: That's the wrong place to put our resources. We can provide the design capacity to meet the building demands. But if we don't solve the problem of airplane security, then our society will continue to face these problems,' Magnusson said, adding that other buildings, such as sports venues, are at risk of attack from the air by airplanes, which continue to be made larger. For example, the Air Bus A 380 airplane, which is four times larger than the 767s that hit the Twin Towers, will be flying by 2006, Magnusson said.
The task force's report, 'World Trade Center: Building Performance,' which will be released in about two weeks, will show that the Twin Towers performed well, but simply were unable to resist the impact from the 767s that have a wing span of 156 feet, were loaded with fuel and were traveling at 586 mph. 'The fact that the towers withstood the initial impacts created false expectations of their ability to stand. Ninety-nine percent of all buildings, if hit by a plane like that would not withstand the impact,' said Magnusson.
While the fires, which resulted from the crashes, damaged and eventually weakened the towers, Magnusson said that their ultimate collapse was a result of the impacts. 'There is really nothing about the event that says our fire codes were good or bad,' he said.
During his presentation, Magnusson showed a compelling video of the towers' collapse filmed by someone in the New York office of the architecture firm of Skidmore Owings & Merrill, whose offices on in a building nearby Ground Zero.
