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The London Millennium Footbridge has an unusual low-slung suspension design, supported by steel cables anchored to piers on the opposite river banks. When opened in 2000, it was found that low-frequency lateral vibrations were excited by pedestrians. To reduce the amplitude of these swaying oscillations, modifications were made in two ways. One was to install, under the bridge deck, passive tuned-mass vibration absorbers of broadly conventional design. The other was to add damping by introducing linear viscous dampers. These modifications had to be made without altering the visual appearance of the bridge. That made the design of viscous dampers difficult because most of their only suitable locations were where the relative amplitudes of vibration were small. A key feature was therefore to deploy dampers that could work with very small amplitudes of movement. The design of both tuned-mass absorbers and viscous dampers will be reviewed. Proving tests, involving 2,000 people walking over the modified bridge, and the subsequent service experience, including the results of examinations by the manufacturers after 15 years’ service, will be described. An opportunity for IIAV members to visit the bridge is included in the ICSV24 programme.

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