Dr. Charles Thornton

Engineer explores structural reasons for WTC collapse

Noted structural engineer and visiting University lecturer, Dr. Charles Thornton, spoke yesterday about the engineering analysis of the September 11 terrorist attacks on the World Trade Center. Thornton, chairman of the engineering firm responsible for assessing the damage at the WTC site, explained the reasons for the catastrophic collapse of the twin towers.

Thornton confirmed the widely reported structural explanation for the towers' collapse. "No aircraft alone will knock over an office building" as massive as a tower at the World Trade Center, he said.

The burning jet fuel weakened the building's structural supports, but as to what specifically failed, he admitted, "I don't know if anybody will ever know for certain."

He noted several measures that could have improved the buildings' chances for survival under such an assault. "I might use a concrete core [rather than the steel in the WTC], or I might encase the beams in concrete," Thornton said.

Reinforced concrete can survive intense heat far better than steel, he said. The beams of the twin towers were made of steel with an applied fire retardant coating.

Thornton referred to the Petronas towers in Malaysia, which his company — the Thornton-Tomasetti Group — designed. Those twin towers, currently the tallest in the world, have concrete beams arranged in a circular pattern, which gives added strength against wind and other stress. "There's no way an aircraft goes through a thirty-inch concrete wall," he added.

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