Swaying bridge stays shut

Engineers are still investigating why the bridge sways

The £18m Millennium Bridge could stay closed for up to three months as engineers investigate ways to stop it swaying.

Giant shock absorbers may be needed to stop the wobble, according to a taskforce of 20 experts carrying out tests on the river Thames footbridge which closed two weeks ago.

I would rather be accused of being over ambitious than be lily-livered

Architect Lord Foster

The bridge, dubbed a "blade of light" by promoters, proved popular and was used by about 150,000 visitors in the first three days before it was closed because of excessive movement.

Tests by engineers Arup since the closure have included a "grandstand shaker" and asking 20 men to sway from side to side to measure how the structure responds.

Arup's chief engineer Tony Fitzpatrick said tests were still under way but the "synchronised footfall" effect of hundreds of people stepping in unison was the cause of the swaying.

Shock tactics

Mr Fitzpatrick said no study of such a problem had ever been undertaken and there was no way the engineers could have predicted it.

"I am disappointed but not ashamed," he said.

Design team Tony Fitzpatrick, Lord Foster and Sir Anthony Caro

He called for the engineering industry to set up a troubleshooting team to explore such untested problems.

The bridge spans the Thames between St Paul's Cathedral north of the river to the Tate Modern at Southwark on the south bank.

Engineers have ruled out the possibility of stiffening the structure but may try to use shock absorbers to soak up the swaying.

How many dampeners are needed and where they need to be put along the bridge still has to be investigated. They will then have to be especially made for the project which could take several months.

"There will be big changes, it isn't about tinkering around at the edges," Mr Fitzpatrick warned.

Ambition

The cost of the work has still not been estimated and who foots the bill is still to be decided.

The completed bridge, owned by the London Borough of Southwark, is already reported to have been £2m over budget.

Security men restricted access to the bridge before it closed

Architect of the bridge Lord Foster said he was bitterly disappointed, but insisted the problem was not a safety issue and would not have chosen any other design.

"I would rather be accused of being over ambitious than be lily-livered and retreating into a nostalgic past that never existed," he said.

David Bell, chair of the Millennium Bridge Trust, which added more than £7.1m to £3.5m from the Corporation of London, promised that the solution would be the best for the people of London.

He said it would ensure that there would never again be a need to ration the number of people wanting to cross the bridge.