A week before the Sept. 11 terrorist attacks on the World Trade Center, structural engineers met at a conference in Frankfurt, Germany, and wondered aloud about how to build taller skyscrapers.
Today, they will join architects and other building experts in Chicago for a far more sober discussion: Will such high-profile symbols of power and prestige be built any time soon -- and, if so, what can be done to make them safer and more secure?
Chicago is an appropriate choice for debating these issues, and not just because the city is home to Sears Tower, the nation's tallest building.
Even as others argue that supertall buildings will forevermore be prime terrorist targets, New York City developer Donald Trump is still planning a Chicago office-condominium tower that could rise as high as 1,300 feet -- only about 65 feet shorter than the destroyed trade center towers.
But no U.S. developer, not even one as successful as Trump, will be able to get financing for such a prominent skyscraper today, predicts Eugene Kohn, a partner in the New York City architectural firm of Kohn Pedersen Fox.
"There is an emotional reaction to the tall building," Kohn says, citing World Trade Center survivors who have told him they have no desire to work again in a high-rise.
Kohn will be among the experts prognosticating the future of the skyscraper Monday as the Council on Tall Buildings and Urban Habitat, an international group of architects, engineers and other building experts based at Lehigh University in Bethlehem, Pa., holds an all-day session on the skyscraper's future.
To gauge the sentiments of the experts speaking at the meeting, to be held at O'Hare International Airport, the Tribune interviewed several of them beforehand. Some, like Kohn, say it could be a decade before another supertall tower is built in the U.S. Others, like Trump's architect, Adrian Smith of Skidmore, Owings & Merrill, forecast that such a project could get under way in just two or three years.
Yet in light of the World Trade Center's stunning collapse, all the experts agreed, it would be wise to rethink the design and construction of skyscrapers, especially those that top 1,000 feet and are therefore considered supertall.
"Whenever a building falls down, there's a lesson to be learned," says William Baker, a structural engineer at Skidmore, Owings & Merrill and a member of an engineering team that is studying the New York City disaster.
Citing examples in Europe and Asia, the architects and engineers suggested everything from wider fire stairs that will enable people to get out of buildings more quickly to "refuge floors," heavily fireproofed floors where people can gather below a fire.
Skyscrapers might be equipped with special elevators for firefighters, they said, while underground parking garages at skyscrapers could be banned, eliminating a spot from which terrorists can strike. New structural techniques, such as heavyweight concrete cores, also might save lives.
The big question underlying all the proposals is whether a new set of assumptions -- and thus, a new set of building codes -- should govern the design of supertall skyscrapers.
Currently, codes assume emergency conditions requiring escape from a fire confined to one or two floors of a skyscraper. Now, should codes reflect the danger posed by the much larger fires and structural damage that results when a jetliner hits a building? Or was Sept. 11 a one-time event?
Everything depends, Smith says, "on whether you are planning for a terrorist attack. If you're planning for that, then there are a whole host of things you have to do."
Many of the experts said it would be foolish to place too much responsibility on building design and management, because the chief cause of the World Trade Center's collapse was the hijacking of two jetliners and the transformation of those planes into flying bombs.
"I think security has to start on the airplane," says Thomas Fridstein, director of design for the New York-based developer and building owner Tishman Speyer.
Above all, the experts are warning people against overreacting. Historically, they say, skyscrapers have been very safe places, with only a small number of deaths resulting from fires and structural collapses.
Moreover, they point out, the U.S. has only eight supertall buildings to worry about: Sears Tower, the John Hancock Center and the Aon Center (the former Amoco Building) in Chicago; the Empire State and Chrysler Buildings in New York; and one supertall tower each in Los Angeles, Houston and Atlanta. And some of these skyscrapers seem to be unlikely targets.
Experts' goal: To make buildings terror-proof
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