A volunteer at Ground Zero of the Sept. 11, 2001 terrorist attacks examined the fall of the World Trade Center towers from a structural perspective at a lecture titled “World Trade Center Collapse: Observations from Ground Zero.”

Kevin Michols, a professional structural engineer who spoke to students Monday, was called out to Ground Zero by the National Council of Structural Engineering Association of New York. Michols spent one week there two weeks after the terrorist attacks.

Michols worked in a quadrant at the site where World Trade Center No.7 had collapsed. The goal of structural engineers is to collect and preserve data, do preliminary analysis, make recommendations for additional study and recommendations to improve buildings, Michols said.

Michols talked about what rescue workers had to deal with at Ground Zero.

“Every time they moved a piece of steel, they didn’t know if others would fall and had to be careful,” Michols said.

Fire often flared up while moving the wreckage, and even a month later steam was still rising from the ground, Michols said.

There were narrow escapes for several rescue workers, Michols said.

“In the Banker’s Trust building, workers walked on a floor, then went down to the next level, looked up, and noticed there were no floor beams supporting the ceiling. The impact of the attacks had caused the floor beams to tear off,” Michols said.

People were on the first and second floors of the Marriott and walked out because of the structural strengthening done in 1993 after terrorists bombed the World Trade Center, Michols said.

The clearing of Ground Zero was a tedious task. Every little thing had to be assessed, Michols said.

“If a manila folder was found, it would have to be examined then handed to the FBI and the Secret Service,” Michols said.

Buildings surrounding the site had to be netted because the wind would blow glass and debris from busted windows, Michols said.

Over 100 excavators were used on the site. Excavators have jaws which pick up steel piece by piece, Michols said.

Workers put markings on pieces of steel to aid in research of the building. For example, a piece of steel with the number 90 would mean it was from the 90th story, and if it was marked with the letter ‘A,’ it would be from the north tower, Michols said.

The steel pieces were put on barges and shipped to two landfills for recycling, Michols said.

The World Trade Center towers were a “marvel of engineering,” Michols said. The structures were modern and unique, the columns around the perimeter were tight, and the floors were comprised of engineered steel trusses and were concrete-filled, Michols said.

There were a few differences between the north and south towers when they were attacked. The north tower was hit higher up, it stood for one hour and 42 minutes, and the plane that hit it was going 470 mph.

The south tower was hit lower, stood 56 minutes and the plane that hit it was going 590 miles per hour, Michols said.

“A fully-loaded 767 (plane) going at those speeds created a tremendous amount of force. They were able to cut right through the buildings,” Michols said.

The towers weren’t blown apart, but they instantly caught on fire, which caused them to collapse.

“Jet fuel fire burns extremely hot,” Michols said.

The Trade Center is not designed for such a catastrophic event, Michols said. There were sprinkler systems in the towers, but they were damaged; thus there was not enough water, Michols said.

Although the towers eventually collapsed, they stood strongly for a decent amount of time.

“(The World Trade Center towers) performed admirably,” Michols said.

An audience member asked if the towers will be rebuilt.

“(Ground Zero) is owned by the city; the owner has a long-term lease on the site,” Michols said. “It’s a sensitive situation; the developer and the city are being sensitive of what should go there.”

Paul Brewer, a firefighter with Lincoln Fire Protection District, attended the lecture and found it very informative.

“As a firefighter, I’m concerned how buildings are put together,” Brewer said.

The report by the American Society of Civil Engineering on its Ground Zero findings can be found at http://www.asce.org.

The lecture was held Monday afternoon as a part of the centennial celebration of Eastern’s School of Technology.