Back issues — June 2000

Troubled waters

engineers at Ove Arup & Partners believe that the problems encountered by the Millennium Bridge will lead to a “complete rewriting” of the British Standard for suspension bridges.

Arup is keen to counter criticism of the problems that led Matthew Wells, director at Techniker, to call the bridge an “engineering tragedy”. Roger Ridsdill Smith , the structural engineer who worked on the bridge from its conception, conceded that the blame for the problems rested with Arup.

However, he added: “The current movement in the bridge is unacceptable but nobody could have foreseen the problems that are affecting the structure. I believe the issues surrounding the swaying in the bridge will lead to a complete rewrite of the guidance relating to suspension bridges.”

The British Standard for suspension bridges was published in 1978 and amended in 1983.

Ridsdill Smith also hit back at suggestions that Arup had got its sums wrong in the design work for the bridge. He said: “Two separate teams within Arup looked at the project in isolation from one another and came up with the same figures. The scheme was then independently examined by Mott MacDonald. Nobody could have guessed that there would be swaying of this sort.” One line of inquiry is looking at the interaction of the different materials in the bridge.

n Postscript: In fact the standard for suspension bridges was never “completely rewritten”. Instead , a paragraph was inserted saying special consideration should be given to bridge designs with a natural frequency that makes these prone to the problem of pedestrian-induced swaying.