Millennium Bridge

When the New Millennium bridge opened in London in June 2000, it was only natural that Allan McRobie's family urged him to visit. They knew that as an expert on bridge dynamics he would find it interesting. Unfortunately the opening coincided with the end of year exams and Allan was too busy marking projects to go. His kids returned full of enthusiasm, especially about the swaying motions they had encountered. By the time he had chance to visit the next weekend, the bridge was shut. Determined not to miss out on the fun, and also curious to discover more about the reasons why the bridge swayed excessively as people walked across it, he decided to model the structure himself.

"Since I have been at Cambridge, in the Structures Laboratory, I have learned that the best way to tackle a problem is to think about it, decide on the critical experiment and then test it out," explains Dr Allan McRobie. Within a week he had built a model of a section of the New Millennium bridge in the Structures lab, which dutifully swayed when people walked across it. He soon realised that a study of the way people interacted with the bridge as it started to sway was important, and to allow people to walk further on his small bridge would require a moving platform:a critical decision, that led him to interact with Dr Joan Lasenby. Allan knew that Joan, as a competitive runner, would probably have an exercise track. Not only did she come up with the track to put on the bridge, but also had a system of analysing people's gait while walking on it.