|
|
Sears Tower:
A Public Radio Commentary
by Bill Hammack
Listen using RealAudio
Recently I took my nephew to Chicago's Sears Tower to show him a
true American artform: Egypt has its pyramids, Europe its grand
cathedrals, America its skyscrapers. They embody the American
ideals of progress, of newness, of building a nation from
scratch. Here's the most American of actors, Jimmy Stewart,
spelling out this ideal in Its a Wonderful Life:
"Mary, I know what I'm gonna do tomorrow, and the next day, and
next year, and the year after that. I'm shakin' the dust of this
crummy little town off my feet and I'm gonna see the world! ...
and then I'm gonna build things. I'm gonna build airfields, I'm
gonna build skyscrapers a hundred stories high, I'm gonna build
bridges a mile long!"
The Sears Tower, a skyscraper over a hundred stories tall, was
designed by the American engineer Fazlur Khan. That doesn't sound
very blue-blooded, but this Bangladesh-born engineer followed a
very American tradition: He immigrated here.
In 1955, newly graduated from the University of Illinois, he
began working in Chicago designing the bridges, airfields, and
skyscrapers dreamed of by Jimmy Stewart. 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 strong 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
began in an age 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 2000 William S. Hammack Enterprises
|
|
