Major Project to Replace Bridge Bearings

A new report to the Forth Estuary Transport Authority (the body responsible for the operation and maintenance of the bridge) recommends accepting Balfour Beatty Civil Engineering’s bid of £13.6 million to carry out the works. FETA’s engineers had previously estimated a contract cost of £15 million.

The contract involves the replacement of all the bearings on the Forth Road Bridge’s north and south approach viaducts.

The approach viaducts sit at either end of the bridge on each shore, connecting the A90 and M90 with the main body of the suspension bridge. Unlike the middle of the bridge, which hangs from the main suspension 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.

Work on site is expected to start in early summer 2010, continuing through to January 2013.

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.

Barry Colford, Chief Engineer & Bridgemaster at the Forth Road Bridge, said: “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 we replace them now before they present any safety risk.

“This will be the biggest single contract awarded since the bridge opened in 1964. However I’m confident that we’ve got a good contractor and a good price following a competitive tender process.”