1998: Millennium Bridge- London, England

Images: [1] and [2]
Innovation: Millennium Bridge
Location: London, England
Architects: Foster and Partners
Engineering: ARUP
Bridge Length: 325 meters (1,066 ft)
Construction: 1998- June 2010 opening

In the face of height restrictions, engineers chose to place support cables for the bridge under deck level. Eight suspension cables support the aluminum deck via two river piers. Two days after the bridge opened, unexpected vibration led officials to close the structure. The vibration was caused by a positive feedback phenomenon known as synchronous lateral excitation. Natural swaying motion of people walking across the footbridge caused some lateral sway. When faced with this small sway, people naturally adjust their gate to sway in step with the bridge, which increases the amplitude of vibration. Engineers had not expected this lateral resonant vibration. The problem was fixed by installing 37 fluid-viscous dampers that dissipated energy to control lateral movement and 52 tuned mass dampers to control vertical movement. Renovations took from May 2001-January 2002 at a cost of five million pounds. The bridge reopened February 2002 and is no longer subject to positive feedback phenomenon. [1]

Read more about ARUP’s innovative solution to the vibration here 

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