OREGON STATE UNIVERSITY

OSU ENGINEERS TO DISCUSS TWIN TOWER DESIGN, COLLAPSE

11/02/2001

CORVALLIS - Two researchers in the College of Engineering at Oregon State University will make a presentation as part of the OSU Over Lunch lecture series in Portland to discuss how the twin towers were designed, constructed and ultimately collapsed, and how the cleanup operation under way faces unfathomable challenges and staggering costs.

John Gambatese and Christopher Higgins, OSU assistant professors of civil, construction, and environmental engineering, will co-host the two-part slide presentation on Thursday, Nov. 15, at the Portland Marriott, 1401 S.W. Naito Parkway, on the riverfront.

The free presentation begins at noon, preceded by a reservations-only luncheon at 11:30 a.m. The general public is invited to attend both events, but seating is limited so reservations are requested. To make reservations or get more information, call the OSU Alumni Association at 877-305-3759. Higgins will discuss the original design and construction of the buildings, as well as engineering aspects of the collapse after being struck by the aircraft.

Gambatese will analyze the $10 million-per-day cleanup effort that has been complicated by media attention, volunteer workers, search and rescue work stoppages, fatigue, emotional stress, an unstable site surrounded by the most densely populated real estate in the U.S., fires, and the potential collapse of surrounding structures.

Les Robertson, who designed the World Trade Center twin towers in the late 1960s, invented the viscoelastic dampers used on the buildings to minimize wind vibrations and dissipate earthquake energy. As a doctoral student at Lehigh University in the mid-1990s, Higgins studied with Robertson and did extensive research in the design of buildings with viscoelastic dampers.

Higgins says the impact of a Boeing 707, the largest commercial aircraft of that time, was an original design consideration. But the designers did not anticipate a terrorist attack, or the intense heat generated by the burning jet fuel, which contributed to the collapse of the towers.

"I don't think anybody could have expected this," Higgins said. "Sometimes there are things you just can't design for."

Gambatese calculates the energy of the burning jet fuel to have been the equivalent of 2.4 million sticks of dynamite. By comparison, the implosion of the Kingdome in Seattle was achieved with approximately 1 percent of that energy.

Every floor in each of the 110-story, 1,360-foot towers housed almost an acre of rentable space, Gambatese says. The towers were reduced to 1.2 million tons of debris in a very confined area, presenting a cleanup challenge unlike any undertaken anywhere else in the world.

"Not only do the magnitude and intensity of the cleanup effort create a challenge for the construction crews, but the hazardous site conditions create logistic and resource problems as well," Gambatese said.

Higgins, who cites the World Trade Center as an example of structural art in his teaching, maintains that the twin towers will be long remembered. "They're still considered one of the engineering marvels of the world," he said.

Higgins also has a personal connection to the twin towers. His sister lives just two blocks from the World Trade Center, and witnessed both planes striking the towers.

 

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