Episode notes
In 1996 Southwark Council and RIBA Competitions sought a new pedestrian crossing over the Thames, and a team of Arup, Foster and Partners, and sculptor Anthony Caro won with a blade of light. Linking Bankside to the City of London, the bridge frames the south facade of St. Paul's Cathedral, so tall suspension towers were ruled out. Instead the cables run below the deck, pulled taut with 2,000 tons of force across a 325 meter span. The project skipped an Act of Parliament, relying on local permissions, and cost 18.2 million pounds, 2.2 million over budget. It opened a month late on June 10, 2000, when some 90,000 people crossed, up to 2,000 at a time.
The deck lurched sideways up to 70 millimeters, and limiting crowds did not help, so it closed on June 12. The cause was synchronous lateral excitation: walkers widened their steps to keep balance, falling into step with the sway and amplifying it. Engineers tested people on moving platforms at the University of Southampton and Imperial College London and put up to 275 volunteers on the bridge. Rather than stiffen it, they spent five million pounds installing 37 viscous fluid dampers and 52 tuned mass dampers, and it reopened on February 22, 2002. Londoners still call it the Wobbly Bridge.
- Since 1873 a sign on the Albert Bridge has told marching soldiers to break step
- Earlier lateral sway had been recorded on Auckland Harbour Bridge in 1975 and at Birmingham's National Exhibition Centre
- The Millennium Inclinator on the steep Peter's Hill approach broke down so often it was replaced before the 2012 Olympics and later removed in 2021
- Bill Fontana's 2006 Harmonic Bridge piece played the bridge's amplified vibrations in the Tate Modern's Turbine Hall
- Death Eaters destroy it in Harry Potter and the Half-Blood Prince, though the story is set in 1996 before it was built