Hanging frame installation at Dover
VolkerLaser is continuing with works on the A2 East Cliff Viaduct, installing temporary works to pier two, in order to move forward with the bearing replacement.
The A2 East Cliff Viaduct connects the A2 from the top of the white cliffs of Dover, to the Eastern Docks roundabout, where the A2 and A20 meet. The structure was originally constructed in 1976, but due in part to the age and the coastal conditions, the bearings were identified as requiring replacement.
The structure needs to be supported by temporary works and hydraulic jacks during the bearing replacement at each pier, with bespoke solutions being developed for different sections of the viaduct. At the lower piers, a trestle system has been designed to bear directly onto the pile cap. At the taller piers, a high-level solution was required to minimise port disruption, therefore a hanger frame solution was developed.
The 50-tonne hanging frame was constructed at ground level on four concrete plinths, and the hanger beams, which connect the frame to the structure, were pre-installed onto the pier support 13m above the hanging frame.
The hanger beams and hanging frame were connected together using eight Dywidag bars, with each bar having a 60-tonne hydraulic jacking assembly. All eight jacks were energised simultaneously and raised the hanging frame to the underside of the hanger beams in 250mm increments.
The frame needed to be lifted within a tolerance of +/-1mm, which was achieved by controlling each jack using a synchronised lifting system. The full operation took a total of two days to complete the lift, and a further day to connect the hanging frame to the hanger beams.
Mark Waudby, operations manager for VolkerLaser said: “The accuracy of the frame construction location and the hanger beam placement, some 13m above ground level, was critical in the success of this lifting operation, and special recognition must go to Ricky White, our temporary works manager, and Michael Stroud, our surveyor. The lift was complicated and logistically difficult, and special consideration needed to be made for the windy conditions experienced within the port.”