London Millennium Footbridge

The London Millennium Footbridge is a pedestrian-only steel suspension bridge crossing the River Thames in London between the existing Southwark Bridge[?] and Blackfriars Bridge, linking Bankside[?] with the City. It was the first new bridge across the Thames in London since Tower Bridge in 1894 and it is owned by the Corporation of London[?].

The design of the bridge was decided by a competition organised in 1996 by Southwark council. The winning entry was a innovative "blade of light" effort from Ove Arup[?], Foster and Partners and Sir Anthony Caro[?]. Due to height restrictions, and to improve the view, the bridge's suspension design had the supporting cables below the deck level, giving a very shallow profile. The bridge has two river piers and is made of three main sections of 81m, 144m and 108m (North to South) with a total structure length of 325m, the aluminium deck is 4m wide.

Construction began in late 1998 with the main works beginning on April 28, 1999 by Monberg Thorsen and McAlpine. The bridge was completed at a cost of £18.2m (£2.2m over budget) and opened on June 10, 2000 (2 months late) but unexpected lateral vibration (resonant structural response) caused the bridge to be closed on June 12 for modifications. The movements were produced by the sheer numbers of pedestrians (90,000 users in the first day, with up to 2,000 on the bridge at any one time). The initial small vibrations encouraging the users to walk in synchronisation with the sway, increasing the effect.

After extensive analysis, the problem was fixed by the retrofitting of 37 fluid-viscous dampers (energy dissipating) to control horizontal movement and 52 tuned mass dampers (inertial) to control vertical movement from May 2001 to January 2002 at a cost of £5m. After a period of testing the bridge was successfully re-opened on February 22, 2002. The Image below was taken when the bridge was being retrofitted.

The Millennium Footbridge, with St Paul's Cathedral in the background.