Introduction
The Millennium Bridge in London connects Bankside on the south side with the City of London on the north side. At one end it has the Tate Modern art gallery. At the other end it leads to St Paul’s Cathedral.
It’s a footbridge, which had a slightly wobbly start.
Past problem
When it opened in June 2000, thousands of keen visitors waited to cross London’s new bridge. Two days later, it was closed because of the infamous wobble. It remained closed for two years while the reason for its wobble — or swaying — was investigated.
What caused the swaying?
It turns out that random steps from pedestrians provided positive feedback leading to the vibrations becoming uncontrolled.
To avoid this in future, engineers discovered that they need to design their bridges so that a bridge’s frequency is not aligned with the frequency of a typical pedestrian pace.
