Viaduct Bearing Replacement
Last updated on 3 Oct 2012
Current works on site:
Balfour Beatty commenced work on site on the Viaduct Bearing Replacement contract on 17 May 2010 and the project was substantially completed by September 2012.
No disruption to daytime traffic has been caused as a result of this project. It was expected that some overnight restrictions might be necessary to ensure that the jacking and lowering of the bridge deck could be sufficiently controlled, however this did not prove necessary.
A major project to replace the bearings on the Forth Road Bridge’s north and south approach viaducts began in May 2010. The project was scheduled for completion by 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 involved jacking up the deck to allow removal of the existing bearings. The steel box girders that support the concrete deck were 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 was granted. Concrete repairs were 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.
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