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Sears Tower

November 16, 2004

A public radio commentary

Last month an architectural organization officially declared a skyscraper in Taiwan as the world's tallest building. So, today I celebrate America's entry in the skyscraper contest: The Sears Tower, the tallest building in North America at over 1,450 feet.

This American masterpiece came from a very American tradition: An engineer named Fazlur Khan designed the tower. That doesn't sound very blue-blooded, but this Bangladesh-born engineer followed a very American custom: He immigrated here.

In 1955, newly graduated from the University of Illinois, he began working in Chicago ushering in a renaissance in skyscraper construction. This immigrant gave the most American of cities, Chicago, its distinctive landscape, including the John Hancock Building, and, eventually in the early 1970s the Sears Tower.

Sears, a retail colossus at that time, was outgrowing their headquarters and needed bigger ones. Unwilling to move to the suburbs and unable to buy blocks of downtown real estate they decided to reach for the sky. They turned, of course, to engineer Fazlur Khan to build them the world's tallest building.

Khan faced two significant problems in designing the Sears Tower: wind and money. As a building gets taller it becomes more flexible in the wind. To see this, think of a skyscraper as a diving board: If you stand at the end of the diving board: Your weight, like the wind on a building, causes it to flex. If the board is made longer, it will flex more under your weight, unless the board is made thicker. A skyscraper is just like this: The taller it is, the stronger it has to be to resist the wind. And here is where money enters: As a building gets taller, the amount of material needed increases more quickly than its height, and thus the costs escalate - at least by conventional methods. Fazlur Khan found a clever way to cheaply build a skyscraper: make it from square tubes.

To illustrate his idea Khan would take nine cigarettes and squeeze them into a bundle, from the end it looked a bit like a honeycomb. Each tube was a building in itself, but bundling the nine together created great rigidity - and uses less material than conventional ways: Khan's Sears Tower uses about 2/3 the steel of the Empire State Building.

You can see these nine tubes in the Sears Tower. The first fifty floors are nine tubes laced together, following by floors made of seven tubes, then five tubes shaped like a cross, until the final ten floors of two tubes. This gives the Sears Tower its layered structure, which one critic called "a driftwood carving by some giant."

A carving that might well be from a dying breed. Skyscrapers first appeared when corporate giants built self-named monuments to house their workers - New York's Chrysler Building, Chicago's Sears Tower, San Francisco's TransAmerica Pyramid - but will they thrive in this new digital economy? Maybe not. Compare these corporate skyscrapers to the headquarters of today's financial colossus: In Redmond Washington, Microsoft's headquarters is only sixty-five feet tall.

Copyright 2004 William S. Hammack Enterprises