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London's Millenium Footbridge

 

The unexpected result of the bridge’s opening caused huge publicity and the bridge closed two days later! Londoners nicknamed it the “Wobbly Bridge.”

The bridge opened on 10th June, 2000 and was Central London’s first pedestrian crossing over the River Thames for more than a century. The 325 m steel structure linked St Paul’s Cathedral in the City of London on the North Bank with the Tate Modern Gallery at Bankside on the South Bank.

Over 1000 pedestrians crossed the bridge immediately upon its opening. The bridge began to sway in an alarming manner, making those crossing cling to the structure for safety. The bridge was closed on 12th June.

The concerned design engineers investigated and traced a little known phenomenon now called “Synchronous Lateral Excitation.” The bridge swayed sideways as a result of chance correlation of footsteps in a crowd that made the structure self-excite. The problem was resolved when the engineers fitted “passive damping” to minimize the bridge’s movement and the Millennium (No Longer Wobbly) Footbridge reopened.

(My thanks to the Department of Engineering, University of Cambridge for technical details.)

 

 

The Millenium Footbridge

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