Millennium Bridge

The Millennium Bridge is London's first new Thames crossing since Tower Bridge (which was opened in 1894). Designed by Norman Foster as a "blade of light" across the river, the new bridge was "dedicated" by Queen Elizabeth II on May 9, 2000. It openned to the public on Saturday, June 10, 2000.

I've had the privilege of seeing it grow day by day, as I cross the river by Southwark Bridge. It's truely majestic. It's lightness and clean lines contrast starkly with the heavy, industrial bridges either side (Blackfriars Bridge being the other).

Unfortunately, on the opening day, the bridge was struck by bad news. People taking part in the opening walk complained about how much the structure swayed. From the BBC news site (http://news.bbc.co.uk/hi/english/uk/newsid_784000/784927.stm):

Engineers made safety checks to the structure after it was forced to close briefly. A limit was subsequently imposed on the number of pedestrians allowed to cross the bridge.

The engineers stated that the bridge was structurally safe but the owners (the Millennium Bridge Trust) put crowd control measures in place to keep numbers down. As a spokesman for the engineers pointed out, "The bridge is intended to have some movement. It's a suspension bridge - if there isn't movement there can be a problem."

I'll quote further from the BBC:

Those who had made it across before the closure said they had been surprised by the swaying sensation.

Margaret Vint, 60, from Burnham, Buckinghamshire, said: "I think you need to take your sea sickness pills before crossing.

"The vibration was tremendous - I could feel the whole weight of the bridge swaying."

The bridge was closed on Monday night.

Personally, I think it's very sad. The structure is designed to move. Perhaps it moves more than some expected. However, so long as it's safe - i.e. not going to throw anyone to their feet (or over the side!) - I can't see why it should be closed. When it comes down to it, it's too beautiful to fail, just like the London Eye.

There's a good webcam (http://www.mbridge.ft.com/hifat/index.html).

London's Millennium Bridge was closed not for structural reasons, but due to a “small perceived risk to pedestrians of losing balance and coming to harm in crowded situations” due to movements of “unexpected amplitudes”. Videos show up to 50 mm. of flex with a frequency of .77 cycles/second at the ends and 70 mm. flex at .95 cycles/sec for the center span, which caused pedestrians to stop and hold onto the balustrades to regain their balance. (data and quote from subsequent investigation)

Mechanical tests validated the computer simulations done before construction-- unfortunately British bridge building standards only specify vertical excitation and designers did not take into account the structure’s natural frequency, which proved to be similar to the horizontal effect of crowds walking in step. Research and implementation of an expensive plan to add viscous and tuned horizontal dampeners has kept the Millennium Bridge closed to the public for over a year. The tabloids have shown no mercy in exposing this politically embarrassing situation, considering the success of the nearby Tate Modern gallery, the bridge's French connection, and the failure of the Dome.

At long last the bridge is open to the public and is a popular, if notorious, landmark.