Capital Projects:
Viaduct Bearing Replacement
Last updated on 11 Jun 2010
Current works on site:
Balfour Beatty commenced work on site in the compound on 17 May 2010 and survey work to the top of the piers has now been completed. Consultation with the City of Edinburgh Council over issues such as temporary road and footpath closures is ongoing. Further consultations and public meetings with residents are being arranged jointly with Balfour Beatty.
Fencing has been erected around the base of the viaduct piers for safety while the bearing replacement works are carried out. This fencing is not permanent, but will be required for the majority of the works. The path along the disused railway line will remain open throughout the works, as will Shore Road itself.
Excavation works are under way to build a hardcore access track to the base of each viaduct pier. Once this is complete the contractor will begin constructing scaffolding around the piers.
No disruption to daytime traffic is anticipated as a result of the bearing replacement project. However, some overnight restrictions may be necessary to ensure that the jacking and lowering of the bridge deck can be sufficiently controlled.
Background:
A major project to replace the bearings on the Forth Road Bridge’s north and south approach viaducts began in May 2010. The project is scheduled for completion at the end of 2012.
The approach viaducts sit at either end of the bridge on each shore, connecting the A90 with the main body of the suspension bridge. Unlike the middle of the bridge, which is suspended from the main cables, the approach viaducts are supported by reinforced concrete piers. Steel bearings sit on top of these piers, allowing the deck to move as required by changes in temperature and traffic loading.
The project will involve jacking up the deck to allow removal of the existing bearings. The steel box girders that support the concrete deck will be strengthened at the jacking points, and reinforced concrete corbels added to the sides of the piers to accommodate the jacks, an alteration for which listed building consent has been granted. Concrete repairs will be carried out on the piers and a system of cathodic protection installed.
It was always expected that these bearings would need to be replaced after a few decades. Similar replacements have been carried out on viaducts all over the world, most recently in Scotland on the Tay Bridge. Like all moving parts, the bearings will eventually wear out, so it’s important that they are replaced now before they present any safety risk.
Balfour Beatty Civil Engineering have been contracted to carry out the works under the supervision of consulting engineers Atkins, following a competitive tender process involving six potential contractors. Balfour Beatty scored highly for quality and bid £13.6 million to carry out the works.
Related documents:
The Bridge:
Facts & Figures
Opened 1964, 2.5 km long, Main span 1006 metres
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