A POWERFUL new shaking machine will be installed on London's 'wobbly' Millennium Bridge next week as part of a £250,000 trial to prove the £5M solution to sway problems.
Commissioned by structural engineer Arup and assembled in Glasgow by Nicole & Andrew, the new shaker was developed with input from the National Engineering Laboratory in East Kilbride and the Leyland Technical Centre in Preston.
It replaces a smaller machine supplied by research body BRE for trials carried out shortly after the bridge closed in June (NCE 6 July).
This machine was not powerful enough to test the trial assembly of a pair of 'chevron-braced' high performance viscous dampers and a central tuned mass damper. This combination is being installed on the £18M crossing by contractor Cleveland Bridge. Work is already well advanced and the dampers and shaking machine should be delivered by the end of this week.
Once installed, the shaker will generate a range of frequencies of horizontal movement. Accelerometers will measure the response and compare it to the bridge's behaviour before the dampers were fitted, measured during the earlier trials.
Up to 300 volunteers drawn from Arup staff will then be marched across the bridge. Arup is hoping the trials will not only validate its proposals for the retrofit but will even allow it to do without some of the 30 plus dampers originally proposed.