Note

Date 1988

Event ID 1182844

Category Descriptive Accounts

Type Note

Permalink http://canmore.org.uk/event/1182844

Kincardine on Forth Swing Bridge

This bridge was built by the Cleveland Bridge and Engineering Company of Darlington, England in 1936. It was the first road bridge to be built across the River Forth east of Stirling and provided a vital direct link between the counties of Fife (north side) and Stirling (south side). The bridge had become necessary because of the rapid increase in the number of road vehicles during the 1920s and the limitations of the local ferry services. It cost £322,500 to build and came in £60,000 under budget.

The site at Kincardine was chosen because the Firth of Forth widens to three miles immediately to the east towards Grangemouth. The rival site at Alloa was rejected as poorer access for traffic and greater construction costs. The width of the Firth of Forth at Kincardine narrows to a maximum of 2,400 feet at high water. The bridge replaced a small passenger ferry, and the remains of its jetties can still be seen 150m to the west on the upstream side.

Before 1936, the nearest crossing point for vehicles was a steam ferry boat upstream of Alloa and the the closest bridging point was at Stirling Bridge. The Kincardine bridge therefore saved an average detour of 50 miles for road vehicles. Construction began in December 21933 with many people displaced due to the building of the approach viaduct section. An average of 150 people were were on the site during the three year build. It opened to traffic on October 29th 1936.The bridge was built in the open position, so the opening ceremony was actually a closing ceremony allowing traffic to cross the bridge.

The bridge was designed by Sir Alexander Gibb and Partners and was conceived as a multiple span structure with six distinct sections. Of these only the central steel span is the swing section, all other parts being fixed. The six sections combine to form a total span of 2,9696. From south to north , the first section the first section comprises a 265 foot pile-reinforced concrete viaduct. This is followed by a second section of none reinforced -concrete spans of 50 feet, with arched underside beams. Leading up to the central swing spans if the third section of seven steel spans, each 100 feet. On either side of the central swing span are two large concrete portals containing safety gates which descend when the bridge is about to swing. The portals, like the piers of the bridge, are concrete made from English Portland cement. Immediately on the north side of the swing span, the fifth section is an identical sequence of seven steel spans supported on reinforced concrete piers. The final portion is a curved viaduct section of three continuous 62 foot 6 inch spans leading down onto the north bank, over the railway and into the town of Kincardine.

Power for swinging the bridge was provided by an engine room in the base of the central pier, which is supplied by electricity from the Fife shore by underwater cable. The swing sections weigh 1600 tons, and rotate on a radial assembly of 60 solid cast-steel rollers. The entire opening procedure is controlled from a beautifully maintained control room which has retained its original fittings and open switchboards. The control room is suspended in the superstructure of the swing section above the road level.

the opening procedure begins with the sounding of a siren, the changing from green to red of the traffic lights and the descent of the safety gates. All road traffic is forced to stop once the gates begin to descend, and travelers are delayed for at least thirteen minutes.

There are three county plaques displayed on the portals as well as the finish effect on the concrete achieved by using hessian-lined shuttering.

In the control room, the opening procedure is controlled automatically by the original GEC electrical switchgear. Below, in the engine room, a Tangye 25-horsepower hydraulic pump is activated retracting wedges and locking bolts, which freed the central span and allowed it to rest on rollers. The bridge was then ready to open.

Visited by RCAHMS (Dr MK Oglethorpe), 1988.

MS8319