Millennium Bridge

The Millennium Bridge, so named due to its conception and build to honor the passing of the year 2000, has an interesting history. It is in London, England, and crosses the River Thames, linking the City of London with bankside. It is pedestrian only, with Southwark Bridge downstream and Blackfriars Bridge upstream.

Originally designed in 1998, building of the Millennium Bridge began early the next year. In design, it is a standard suspension bridge. It was designed on the concept of being a “blade of light” by Arup, Fosters and Partners and Sir Anthony Caro. Height restrictions required some modification to the classic design of the suspension bridge; so as not to restrict the view, the supporting cables are below the deck of the bridge. The bridge is supported on either side by river piers, and has a maximum height of 472 feet – around 144 meters – above the River.
The Millennium Bridge went over L2 million over budget, in the end costing L18.2 million. It also suffered design setbacks and opened two months late, on 10th June 2000. This, however, was not the end of the troubles for the Millennium Bridge.

It became apparent almost immediately that the bridge suffered from a terrible wobble-motion when used by the pedestrians for which it had been designed. The bridge was reported to sway back and forth, making it very difficult to stay upright on. The effect, while unusual, is known and is referred to as  Synchronous Lateral Excitation. This essentially means that the natural sway of people walking on the bridge caused sideways movements of the bridge itself, which was particularly reinforced with the amount of traffic using the Millennium Bridge in its opening days. This movement in turn creates people to try to counter the movement and sway in step, which serves to only make the sway of the bridge itself worse; this is known as positive feedback.

The wobble was of such concern that the bridge had to be closed not three days after being opened, much to the chagrin of the British public. In fact, in its early life the only positive feedback the bridge did receive was based on the strange physical sway caused by the bridge. The British public saw it as another waste of money in efforts to celebrate the Millennium; the ill fated Millennium Dome, a catastrophic failure, was fresh in the memory.

The problem was eventually resolved by the installation of vibration dampeners, and since the Millennium Bridge reopened in February 2002 the problems have not recurred. The only other time the bridge has been closed was during the Kryill Storm, when high winds caused worry that pedestrians would be blown from the bridge due to its high profile deck – a result of the low slung suspension required to solve the problem of height restrictions.

The Millennium Bridge, despite seven years of good service, remains something of a national joke in the eyes of the British public due to its cost and problems. It is set to star in the 2009 film Harry Potter and the Half Blood Prince, where it takes the place of a bridge originally written about in the novel of the same name which collapses. While film makers insist the bridge was chosen for its iconic status rather than its less than perfect safety record, one has to wonder if this is entirely true.