What year was the Millennium Bridge built

What rocked the Millennium Bridge

Shortly after its completion in 2000, pedestrians vibrated the Millennium Bridge in London violently. The problem was only solved by installing additional dampers. Passers-by walking in unison were responsible for the resonance phenomenon. The synchronous behavior of the pedestrians was triggered by the initially very weak vibrations of the bridge. How these first oscillations came about has not yet been conclusively explained. To close this knowledge gap, physicists now modeled the forces exerted by pedestrians on the bridge in more detail than in any previous study. In the journal "Science Advances" they report that a minimum number of passers-by was necessary to stimulate the very first vibration. Your model could now be used by architects to make bridges and football stadiums more stable.

"When pedestrians cross a bridge, they interact with the structure and can make it vibrate," explains Igor Belykh from Georgia State University in Atlanta. In order to better understand this effect, he and his colleagues developed a special mathematical model. In this, the team took into account the forces that passers-by exert via their feet with every step on a bridge construction. In the case of the Millennium Bridge, Belykh sees the previous explanation that a group of passers-by happened to walk in unison as too simple. In the new model, the scientists therefore linked the forces exerted by passers-by, described as oscillators, with the bridge structure and its structurally given resonance frequency. The researchers concentrated on generating the first weak vibrations. The result: only from 165 people the forces acting via the feet are sufficient to set the bridge in London in a small initial oscillation.

According to Belykh and his colleagues, the detailed pedestrian model could be used for virtual "crash tests" in the planning phase of bridges and other structures. With additional damping elements, a resonance frequency that can only be excited by pedestrians can be shifted from the outset to another harmless frequency range. With their new model, the researchers now want to analyze other bridges - for example at the airport in Singapore or the Clifton Suspension Bridge in Bristol - that were already showing suspicious vibrations. The scientists also see an important field of application in the construction planning of football stadiums, in which fan groups like to move in unison.