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Robertson, WTC Designer, Lectures on Center, Future

By Jennifer L. Wong


Leslie E. Robertson, one of the two engineers who designed New York’s World Trade Center, gave the Felix Candela Lecture Tuesday evening, discussing buildings he has designed around the world and the future of the Trade Center site.

The Felix Candela Lecture is an annual event honoring a leading structural engineer and is organized by MIT, Princeton University, and the Structural Engineers Association of New York.

Robertson, a 1952 graduate of the University of California at Berkeley, has been instrumental for the structural design of hundreds of buildings. His firm, Leslie E. Robertson Associates, is responsible for three of the six tallest buildings in the world.

Robertson discusses construction

Robertson began his lecture by recognizing the skills and diligence of the people who worked with him on his projects all these years. “In order to do great work, it takes many wonderfully talented people,” Robertson said.

A civil engineering graduate, Robertson and his then-business partner John Skilling were the original structural engineers for the Twin Towers. Robertson was just thirty-four years old when he headed the design for the WTC.

In his lecture, he discussed many of his innovative ideas that were used in this major project. Prefabricated steel columns and wall panels were dominant factors in the building process.

Robertson and his team were able to construct the 110-story structure by developing mechanical damping units to reduce wind-induced swaying motion.

He also conducted the first comprehensive environmental studies of boundary layer wind tunnel technology as well as human sensitivity to building movements.

“There was no symmetry in the buildings -- one was designed to shield the other,” Robertson said.

Documenting the construction process with numerous photographs, he displayed how the WTC was pieced together, with each section three columns wide and three stories high. Conveying the complexity of the project, he said “the steel work was done by thirty-nine different fabricators.”

The Twin Towers under attack

Robertson discussed the 1993 terrorist bombing, when an explosion occurred in Tower One’s lower-parking levels.

He showed how five floors of the building collapsed and the “debris landed on the refrigeration machines.”

“The rubble pile helped to prevent the walls of the structure from completely collapsing,” Robertson said.

Robertson continued his lecture by showing schematic diagrams and talking about the extensively detrimental effects of the jet fuel in the collapse of the towers after the 2001 terrorist attack.

As a basis of comparison, the bomb that destroyed the Oklahoma City Federal Building in 1995 was equivalent to 192 liters of jet fuel, Robertson said.. The Boeing 767 that struck the first tower in the Sept. 11 attacks carried 45,600 liters.

The towers were “designed to withstand the accidental impact of a Boeing 707,” the largest aircraft flying in 1966, when the project broke ground, he said.

Robertson said that the towers could have survived that fateful Tuesday morning, but “the fires that were ignited by the fuel were the real problem.”

Despite the circumstances, Robertson said “the World Trade Center had performed admirably” in standing as long as it did and allowing those who had the opportunity to evacuate to do so.

Robertson shows other buildings

Robertson continued by highlighting various buildings he was commissioned to do as well as mentioning experiences with notable architects.

He worked with architect Philip Johnson in designing the AT&T corporate headquarters, now the Sony Building, in New York City.

Robertson collaborated with highly-esteemed I.M Pei ’40 to design the Bank of China Tower in Hong Kong. “It was the tallest building in the world outside of New York and Chicago when it was constructed,” he said.

Robertson is currently working on the Shanghai World Financial Center in China, which is slated to be the world’s tallest building when completed.

Thinking about the future

At the conclusion of the lecture, Robertson fielded many questions from the PhD candidates in the audience about what engineers were thinking about for the future.

When Gabrielle E. Rieckhof, a postdoctoral fellow, asked what Robertson thought should replace the World Trade Center, Robertson said he hoped for a “commercial shopping district to liven the area and a new underground transportation system.”

“I would like to see at least one very tall building,” he said.