I was interested to see Professor Fujino mentioned (NCE 6 July), because my recent PhD at Imperial College was a development of one of his lines of research into damping. Tuned mass dampers of the classic form in use worldwide (including Europe's longest span at Storebaelt) have a major problem for applications such as this: they are very sensitive to correct tuning.
The Millennium bridge will change its tuning according to the mass of people on it, as well as temperature. The solution is the Multiple Tuned Mass Damper (MTMD) where there are separate masses tuned to slightly different frequencies.
Dr Viken Chinien, Imperial College of Science, Technology & Medicine, Department of Mechanical Engineering, Dynamics Section, South Kensington, London SW7 2BU