WOBBLING OF PEDESTRIAN BRIDGES

On June 10, 2000, the Millennium Bridge in London opened to the public. As people crossed it, it wobbled, leading to its closure three days later. It reopened after modifications to prevent the wobbling were made. To gain understanding on the physics behind this event, we developed and studied a toy model of a pedestrian-bridge system. Within this model, when the natural frequency of the bridge is the same as the walking frequency of the pedestrian, the lateral oscillations of the bridge and the pedestrian synchronize in antiphase. The model predicts the amplitude of the bridge oscillations.