Within the next two weeks engineer Ove Arup will unveil its proposals to stop the wobbling Millennium Bridge from swaying at an estimated cost of Â£2 million. There are serious concerns, however, that Lord Fosterâ€™s Thames footbridge will need a further Â£10 million of remedial work before it can be opened to the public.
Ove Arup is expected to favour a system of dampers to bring stability to the Â£18 million "blade of light", a method which some experts believe will be ineffective. "Maybe dampers will work," said the Tokyo-based bridge specialist, Professor Yozo Fujino, "but Iâ€™m not very confident. The problem is that the bridge is very light and human forces are very large."
Fujino identified the problem of "synchronised footfall" in a paper written in 1993. This report has subsequently been consulted by engineers around the world including Techniker, the firm behind Londonâ€™s Royal Victoria Dock footbridge that opened in 1998. "If you do advanced and sophisticated things, then you should make sure you read the literature first," said Technikerâ€™s director Mathew Wells.
Ove Arup failed to consult Fujinoâ€™s paper, considering it to be obscure, but it did undertake "dynamic analyses" and wind tunnel tests as well as consulting an independent firm of engineers before proceeding with the design.
Another bridge expert, Dr Arvind Kumar, advises the Corporation of London and was one of over 200 entrants in the Millennium Bridge design competition. Kumar believes that more drastic measures are needed to make the bridge safe. "You canâ€™t totally rectify the bridge except by raising the height of the cables which would cost up to Â£10 million," he said.
Whatever solution Ove Arup propose, it is clear that the cost will run into of millions of pounds. What is not clear as of yet is where this additional funding will come from. The Millennium Commission, private financiers and the projectâ€™s insurers can all expect a visit in the near future.
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Estimated extra cost of clearing bombs is somehow estimated at Â£18m, which makes Foster's blunder look cheap.
No-one has yet explained why nobody told the bridge builders about the bombs until so far on in the process, or why London Underground suddenly thought of it...or why on earth it should cost so much to clear them...or why they weren't cleared years ago... etc etc.
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Oh yeah? I hear recent trials showed that a mere fifty (50!) people, walking in unison, can made the bridge 'take off', swaying from side to side.