Millennium Bridge, London
Tuesday, 22nd May 2007 by Alex Turnbull
The first pedestrian crossing of London’s Thames river in over one hundred years, the Millennium Bridge was conceived as part of the high-profile Millennium Project. Opened on the 10th of June 2000, it was closed again just three days later when it became apparent that the large numbers of people crossing it were causing the whole structure to sway nauseatingly…
The initially small natural vibrations of the bridge encouraged the pedestrians to walk in sync with the movement – which only served to amplify the effect. These vibrations began to occur when there were comparatively few people on the bridge, so by the time there were around 2,000 people on it at once, the wobbling had become pretty dramatic [Youtube link].
Lateral movement of this type in bridges was well known (most famously having caused the complete collapse [Youtube link] of the Tacoma Narrows bridge) – yet this driven harmonic motion caused by the movement of pedestrians remained unanticipated throughout the pre-construction analysis of the bridge.
The Millennium Bridge was closed from June 2000 until February 2002, and even though the problem has now been resolved, it will forever be known simply as The Wobbly Bridge.
More about the London’s Millennium Bridge, as ever, at Wikipedia.
Thanks to Rory and Tim.