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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 http://www.millennium.gov.uk/ 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…

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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, http://www.youtube.com/watch?v=eAXVa__XWZ8 the wobbling had
become pretty dramatic [Youtube link].

Lateral movement of this type in bridges was well known (most
famously having caused http://www.youtube.com/watch?v=P0Fi1VcbpAI 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 http://en.wikipedia.org/wiki/London_Millennium_Bridge London’s
Millennium Bridge, as ever, at Wikipedia.

Thanks to Rory and Tim.

Tags: , bridge, London, Millennium