by Michael J. Crosbie
London’s Millennium Bridge reopened on February 22, 2002, with its designer, Lord Foster, in attendance, but without its original, notorious wobble. Described by Foster as a "blade of light," the Millennium Bridge was closed just two days after it first opened in June, 2000, because it shimmied and shook uncomfortably.
Two years ago, throngs of pedestrians on the 1050-foot- (320-meter-) long bridge, which arcs between St. Paul’s Cathedral on the north bank of the Thames River and the Tate Modern Gallery on the south bank, helped send the bridge into its swaying state.
More than 150,000 people crossed the bridge that first day, and the engineering firm Arup did not anticipate that the pedestrians would fall into an "unintentional synchronization of walking," according to Tony Fitzpatrick, Arup's chief engineer for the project.
As the 13-foot- (4-meter-) wide bridge swayed, pedestrians compensated by adjusting their gait, which magnified the movement. Officials first tried to limit the number of pedestrians on the bridge, but when that did not seem to help they decided to close the span to allow engineers to study the problem.
Bridge as Art
With or without its bounce, the Millennium Bridge is a breathtaking symbiosis of architecture, art, and engineering. Norman Foster worked closely with sculptor Anthony Caro and Arup to create a thin ribbon of stainless steel and aluminum, raised on just two Y-shaped concrete pylons 36 feet (11 meters) above the Thames.
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