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Kincardine Bridge
River Forth, Fife and Stirling, Scotland, UK
Kincardine Bridge
associated engineer
James Guthrie Brown
Sir Alexander Gibb & Partners
date  December 1933 - October 1936
era  Modern  |  category  Bridge  |  reference  NS924871
ICE reference number  HEW 1561
photo  © and licensed for reuse under this
Until Kincardine Bridge was built there was no road crossing over the River Forth downstream of Stirling. At the time of construction, Kincardine was the largest swing bridge in Europe, and Scotland’s longest road bridge. Though the Forth Road Bridge and, more recently, the Clackmannanshire Bridge have relieved its traffic load, Kincardine Bridge remains in continual use.
At the point Kincardine Bridge crosses the Forth, the river is 732m wide at high water. The bridge is 822m long and its high water clearance is just over 9m. Its construction cut the journey from Edinburgh to Dunfermline by 32km. The consulting engineer was James Guthrie Brown (1892-1976) of Sir Alexander Gibb & Partners.
In the 1930s, the Forth was navigable right up to Stirling 16km away, and vessels of up to 2,032 tonnes brought cargoes of coal, oil and timber to the port at Alloa. To accommodate shipping, a 110m long steel truss turning section was incorporated into the bridge. It swings 90 degrees about a central support, providing twin openings of 45.7m.
The circular track and rollers at the central support were made so finely by Sir William Arrol & Co that it required only 1.5kW of power to turn the cantilever spans, which weigh 1,626 tonnes. A long concrete pontoon sits at right angles to the bridge, to accommodate the cantilevers when the swing bridge is open. Opening or closing the bridge takes 13 minutes.
There are 10 approach spans of between 18.9m and 30.5m north east of the turning section, and 16 approach spans of between 15.2m to 30.5m south west of it. They consist of steel girders supported on concrete piers. The southern approach includes a piled reinforced concrete viaduct, some 81m long.
The Kincardine end of the bridge is founded on solid rock. Here, the pier foundations consist of open-topped steel cylinders, 4.4m in diameter, which were sunk to bedrock and pumped out before being filled with concrete. In the middle of the river, where the foundations are 15m under water, closed cylinders were used with compressed air at 152kN per sq m (1.5 atmospheres) to enable dry working. On the Airth side, faulted rock is overlain with gravel and mud, so piles were driven through 15m into firm gravel for the pier foundations.
The bridge cost £327,000 to construct. Shipping activity has decline on the Forth and the bridge's swing section last opened in 1988. It was locked shut in 1989, though the original machinery remains in the plant room on the central pier. The bridge was designated a Category A listed structure in February 2005.
Traffic volumes were reduced when the Forth Road Bridge, some 22km to the east, opened in 1964. However, Kincardine Bridge is still the most downstream all-weather crossing of the Forth and is used when the other bridge is closed to high-sided vehicles in high winds. Congestion was eased further when the Clackmannanshire Bridge (NS920878) opened in November 2008.
Contractor: Cleveland Bridge & Engineering Co Ltd, Darlington
Steelwork and swing turntable: Sir Willima Arrol & Co Ltd
Concrete fill: Tunnel Cement Co, London
Concrete fill: Cement Marketing Co, London
Lamp standards: Bromsgrove Guild
Research: ECPK
"Alexander Gibb: The Story of an Engineer” by Godfrey Harrison
Geoffrey Bles, London, 1950, second edition 1966
reference sources   CEH SLB

Kincardine Bridge