Page 1 of 10
Photo, Sir Alexander Gibb and Partners
TWENTY-SEVEN SPANS and an approach viaduct, 265 feet long, make up the total length (2,696 feet) of Kincardine Bridge across the Firth of Forth. A temporary structure built from either bank on timber piles was provided to carry a double line of railway track for gantries, wagons and cranes during the building of the bridge.
LINKING THE WORLD'S HIGHWAYS-1O
EUROPE'S LONGEST SWING BRIDGE
Across the Firth of Forth at Kincardine is a magnificent road bridge whose central span, 364 feet long, is pivoted on a central pier. This span is opened by electric controls to allow the passage of shipping.
For many years ferries have linked the north and south shores of the Firth of Forth, but most of the road traffic for central Scotland has had to make the crossing of the Forth at Stirling. In 1922 the average number of vehicles crossing Stirling Bridge in an hour was 150, but in 1935 this figure had risen to 400.
To relieve the congestion, the County Councils of Fife, Stirling and Clackmannan decided to build a new road bridge across the Forth. The site finally chosen was at Kincardine, below Alloa. Kincardine Bridge was designed by Sir Alexander Gibb and Partners, of London, and built by the Cleveland Bridge and Engineering Company, Ltd., of Darlington. The structure has a total length of 2,696 feet. At the northern or Kincardine end of the bridge the first three steel spans, each measuring 62 ft. 6 in., are built on a curve over the track of the London and North Eastern Railway. The curve was necessary to make a junction with a special approach road avoiding the streets of the town. The roadway on the curve is banked and at this end of the bridge is 15 feet higher than at the southern end.
The next seven spans, also of steel, are each 100 feet long and their design is of particular interest. The supporting system adopted is that of the cantilever - well in keeping with bridge practice on the Firth of Forth. Every alternate 100-feet span is made up of a central section, 50 feet long, which rests at either end on girders, 25 feet in length, projecting from adjacent spans. This method of construction permitted the use of the arched girders that are a pleasing and characteristic feature of the bridge. Each span consists of six arched girders which support a roadway 30 feet wide. The roadway is flanked by two 5-feet footways, which are carried on curved brackets cantilevered out from the bridge sides. The bridge piers comprise tapered cylinders of reinforced concrete, arranged in pairs which are joined by curved portal beams carrying the span girders.
In midstream is the magnificent central span. At the touch of an electric control wheel this can be swung on its supporting pier, leaving a clear passage of 150 feet on either side for shipping. This swing span, weighing 1,600 tons, is 364 feet long and its girder work towers 80 feet above high-water level. When closed, the swing span provides 30 feet of headroom above high water.
South of the swing span is another series of seven 100-feet steel spans. Next are nine 50-feet spans of reinforced concrete. A viaduct, also of reinforced concrete, provides the link with the southern bank of the river. This viaduct is 265 feet long, and sweeps slightly downward in a reverse curve to meet the lower level of the south approach. Apart from this reverse curve, however, the bridge is upswept from either end towards the centre span, giving it a graceful appearance when viewed from either shore.
Back To The Kincardine Local History Group Homepage