Forth Bridge

Official Heritage Listing Information and Findings

Listed At: Category A

Discussion:

List Entry Number: LB40370 and LB9977

Description:

Sir John Fowler and Sir Benjamin Baker, 1883-90 (designed and tendered for in 1882); Tancred, Arrol and Co, contractors; Joseph Philips, contractor. 2.5 kilometre, painted steel, cantilever railway bridge crossing the Firth of Forth on N/S axis, linking the counties of Edinburgh and Fife.

3 giant, cross-braced, steel tower structures. Each tower counterbalances 2 arms on either side to provide 2 full cantilevered spans (each being 521 metres long with a 107 metre suspended span truss to centre) and 2 half outer spans. Each tower structure is set on 4 circular-plan granite and concrete piers. Piers to S on sea-bed; central piers on shelf of rock beside Inchgarvie (Dalmeny Parish); piers to N on promontory at North Queensferry.

Superstructure flanked by approach viaducts supported (45 metres above water level) by tapering, rectangular-plan masonry piers. 5 piers to N with 3 masonry arches adjoining promontory at North Queensferry; 10 piers to S with 4 masonry arches adjoining promontory at South Queensferry. Trains pass through round-arch masonry portals at innermost piers, marking start of cantilever superstructure.

Thomas Bouch, 1879. Brick pier remnant at Inchgarvie rock, surmounted by early 20th century cast-iron leading light with sectional lantern, bracketed gallery and diamond-paned glazing.

Statement of Special Interest

A-group with 'Jamestown, Forth Bridge, North Approach Railway Viaduct' and 'Hope Street, Forth Bridge Approach Railway, Truss Bridge' (see separate listings).

The internationally acclaimed Forth (Railway) Bridge is one of the most ambitious and successful engineering achievements of the 19th century. On completion it achieved the longest bridge spans in the world and was the largest steel structure, pioneering the wide-spread adoption of steel in bridge construction. With its distinctive cantilevered design, the Forth Bridge is Scotland's most instantly recognisable industrial landmark. It has become a symbol of national identity in much the same way as the Eiffel Tower in Paris.

The construction challenge posed by the Forth Bridge was immense. It took a five thousand strong workforce seven years to build it using more than fifty thousand tonnes of Siemens-Martin open-hearth steel and 8 million rivets. The bridge was first built in sections, on land, before being dissassembled and sent out on boats for re-erection at the bridge site. The towers rise from massive granite piers, the underwater foundations of which were constructed using 21m wide, submersible wrought-iron cylinders called caissons. The ciassons were carefully positioned on the sea bed before being filled with concrete. Numerous innovations by the principal contractor William Arrol (knighted 1890) included his hydraulic spade and riveting machines, allowing construction to advance at an extraordinary rate considering the scale and complexity of the project. As far as possible, the bridge design utilises natural features including the promontories and high banks at North and South Queensferry and the small outcrop of rock, Inchgarvie in the middle of the Firth.

A bridge crossing the Firth of Forth was first proposed in 1818 by Edinburgh civil engineer, James Anderson. Some engineers believed a tunnel would be a better solution and it was not until 1873 that the Forth Bridge Company was founded. The first contract was given to Thomas Bouch who designed a bridge modelled on his design for the Tay Bridge. However, after the Tay Bridge disaster of 28th December 1879, when high winds blew down the high central girders and around 75 lives were lost, the company felt it would be wiser to employ a completely new design. One brick pier of Bouch's abandoned scheme sits beneath the bridge at Inchgarvie rock - its physical survival contributing to the wider story of the bridge.

John Fowler (knighted 1885) and his colleague Benjamin Baker (knighted 1890) received the new commission. Fowler's background in railway engineering was distinguished having previously designed the first railway bridge across the Thames in 1860, St Enoch's station in Glasgow, and he was a principal engineer of the London Underground system. In preparation for the Forth Bridge, Benjamin Baker conducted experiments on wind pressure using a set of gauges that he installed on the Forth shoreline. Their innovative cantilever design allowed spans nearly four times larger than any railway bridge previously built and it remains the world's longest bridge built on the cantilever principle. Construction was authorised by an Act of Parliament in 1883 and the bridge opened seven years later, on 4th March 1890, with Albert Edward, Prince of Wales, inserting a final inscribed gold plated rivet. The bridge has been in continuous use since then with around 200 trains passing over it each day (2013).

The bridge is known for its distinctive paint colour, called Forth Bridge Red. 7000 gallons of paint are required to cover the surface. Similar in shade to iron oxide, the colour helps to disguise areas prone to rust. The act of painting the bridge is used in conversation to refer to any task that appears to be never ending. Between 2002 and 2011, all earlier coats of paint were removed and a new hard-wearing coating system was applied. The new paint coating, originally developed for North Sea oil rigs, is expected to last for at least 20 years.

The bridge is included on the statutory list twice, both in the City of Edinburgh and Fife Council areas.

List description updated at resurvey in 2003/4, and in 2013.

Bibliography

Original plans National Archives of Scotland. F H Groome, Ordnance Gazetteer Of Scotland Vol. Vi (1885), p232. W Westhofen, The Forth Bridge Centenary Edition (1989) first published as a supplement to Engineering Magazine on 28th February 1890. Third Statistical Account Of Scotland Vol.Xxi (1952), p233. C McWilliam, Buildings Of Scotland - Lothian (1980), pp435-6. S Mackay, The Forth Bridge - A Picture History (1990). C McKean, Edinburgh - An Illustrated Guide (1992), p167. A Menges (Ed), John Fowler & Benjamin Baker: Forth Bridge (1997). Network Rail website, www.networkrail.co.uk/VirtualArchive/forth-bridge/ (accessed 2013).

North Approach Railway Viaduct, Listing LB49652:

Description

Sir John Fowler and Sir Benjamin Baker, 1883-1890; Louis Nelville, engineer for Tancred, Arrol and Co and Joseph Philips, contractors. Mild steel and masonry railway viaduct. Masonry abutments of square snecked rubble with band course above eliptical arches (23 metre span) at either end; 4 spans of mild steel box girders formed with raking vertical struts and light lattice steel parapet above (each steel span 30 metres long) resting on 4 masonry piers of squared and snecked bullfaced rubble set at 25 degree angles to the centre line; whole of viaduct on curve with gradient of 1 in 70.

Statement of Special Interest

A-group with 'Forth Bridge' and 'Hope Street, Forth Bridge Approach Railway, Truss Bridge' (see separate listings).

This viaduct was erected by the Forth Bridge Railway Company as a component of the North Approach Railway, built in association with the Forth Bridge (see separate listing). The North Approach Railway is just over 3 kilometres in length commencing from the abutment at the north end of the Forth Bridge and terminating at Inverkeithing at the former junction with the North British Railway. Like the Forth Bridge itself, this viaduct demonstrates an early large-scale use of open-hearth steel.