|Crosses||Firth of Forth|
|Locale||Lothian, Inchgarvie and Fife, Scotland|
|Maintained by||Balfour Beatty under contract to Network Rail|
|Designer||Sir John Fowler and
Sir Benjamin Baker
|Total length||8,296 ft (2,528.7 m)|
|Longest span||2 of 1,710 feet (520 m)|
|Clearance below||151 feet (46 m)|
|Opened||4 March 1890|
|Daily traffic||190–200 trains per day|
The Forth Bridge is a cantilever railway bridge over the Firth of Forth in the east of Scotland, 9 miles (14 kilometres) west of Edinburgh. It was opened on 4 March 1890 and spans a total length of 8,296 feet (2,528.7 m). It is sometimes referred to as the Forth Rail Bridge to distinguish it from the Forth Road Bridge, though this has never been its official name.
Until 1917, when the Quebec Bridge was completed, the Forth Bridge had the longest single cantilever bridge span in the world, and it still has the world's second-longest single span. The bridge and its associated railway infrastructure is owned by Network Rail Infrastructure Limited. It is considered an iconic structure and a symbol of Scotland.
Prior to the construction of the bridge, ferry boats were used to cross the Firth. In 1806, a pair of tunnels, one for each direction, was proposed, and in 1818 James Anderson produced a design for a three-span suspension bridge close to the site of the present one. Calling for approximately 2,500 tonnes (2,500 long tons; 2,800 short tons) of iron, Wilhelm Westhofen said of it "and this quantity [of iron] distributed over the length would have given it a very light and slender appearance, so light indeed that on a dull day it would hardly have been visible, and after a heavy gale probably no longer to be seen on a clear day either."
Thomas Bouch designed for the Edinburgh and Northern Railway a roll-on/roll-off railway ferry between Granton and Burntisland that opened in 1850, which proved so successful that another was ordered for the Tay. In autumn 1863, a joint project between the North British Railway and Edinburgh and Glasgow Railway, which would merge in 1865, appointed Stephenson and Toner to design a bridge for the Forth, but the commission was given to Bouch around six months later.
It had proven difficult to engineer a suspension bridge that was able to carry railway traffic, and Thomas Bouch, engineer to the North British Railway (NBR) and Edinburgh and Glasgow Railway, was in 1863-1864 working on a single-track girder bridge crossing the Forth near Charlestown, where the river is around 2 miles wide, but mostly relatively shallow. The promoters, however, were concerned about the ability to set foundations in the silty river bottom, as borings had gone as deep as 231 feet (70 m) into the mud without finding any rock, but Bouch conducted experiments to demonstrate that it was possible for the silt to support considerable weight. Experiments in late 1864 with weighted caissons achieved a pressure of 5 tons/ft2 on the silt, encouraging Bouch to continue with the design. In August 1865, Richard Hodgson, chairman of the NBR, proposed that the Company invest GB£18,000 to try a different kind of foundation, as the weighted caissons had not been successful. Bouch proposed using a large pine platform underneath the piers, 80 by 60 by 7 feet (24.4 × 18.3 × 2.1 m) (the original design called for a 114 by 80 by 9 feet (34.7 × 24.4 × 2.7 m) platform of green beech) weighed down with 10,000 tonnes (9,800 long tons; 11,000 short tons) of pig iron which would sink the wooden platform to the level of the silt. The platform was launched on 14 June 1866 after some difficulty in getting it to move down the greased planks it rested on, and then moored in the harbour for six weeks pending completion. The bridge project was aborted just before the platform was sunk as the NBR expected to lose "through traffic" following the amalgamation of the Caledonian Railway and the Scottish North Eastern Railway. In September 1866, a Committee of Shareholders investigating rumours of financial difficulties found that accounts had been falsified, and the chairman and the entire board had resigned by November. By mid-1867 the NBR was nearly bankrupt, and all work on the Forth and Tay bridges was stopped.
The North British Railway took over the ferry at Queensferry in 1867, and completed a rail link from Ratho in 1868, establishing a contiguous link with Fife. Interest in bridging the Forth increased again, and Bouch proposed a stiffened steel suspension bridge on roughly the line of the present rail bridge in 1871, and after careful verification, work started in 1878 on a pier at Inchgarvie.
After Tay Bridge collapsed in 1879, confidence in Bouch dried up and the work stopped. The public inquiry into the disaster, chaired by Henry Cadogan Rothery, found the Tay Bridge to be "badly designed, badly constructed and badly maintained," with Bouch being "mainly to blame" for the defects in construction and maintenance and "entirely responsible" for the defects in design.
After the disaster, which occurred in high winds for which Bouch had not properly accounted, the Board of Trade imposed a lateral wind allowance of 56 lbs/ft2. Bouch's 1871 design had taken a much lower figure of 10 lbs/ft2 on the advice of the Astronomer Royal, although contemporary analysis showed it would likely have stood, but the engineers stated that "we do not commit ourselves to an opinion that it is the best possible" [design]. Bouch's design was formally abandoned on 13 January 1881, and Sir John Fowler, W. H. Barlow and T. E. Harrison, consulting engineers to the project, were invited to give proposals for a bridge.
The bridge is, even today, regarded as an engineering marvel. It is 1.6 miles (2.5 km) in length, and the double track is elevated 151 ft (46 m) above the water level at high tide. It consists of two main spans of 1,710 ft (521.3 m), two side spans of 680 ft (207.3 m), and 15 approach spans of 168 ft (51.2 m). Each main span consists of two 680 ft (207.3 m) cantilever arms supporting a central 350 feet (106.7 m) span truss. The weight of the bridge superstructure was 50,513 long tons (51,324 t), including the 6.5 million rivets used. The bridge also used 640,000 cubic feet (18,122 m3) of granite.
The three great four-tower cantilever structures are 330 ft (100.6 m) tall, each tower resting on a separate granite pier. These were constructed using 70 ft (21 m) diameter caissons; those for the north cantilever and two on the small uninhabited island of Inchgarvie acted as coffer dams, while the remaining two on Inchgarvie and those for the south cantilever, where the river bed was 91 ft (28 m) below high-water level, used compressed air to keep water out of the working chamber at the base.
|Wikimedia Commons has media related to Construction of the Forth Bridge.|
Large amounts of steel had become available after the invention of the Bessemer process in 1855. Until 1877 the British Board of Trade had limited the use of steel in structural engineering because the process produced steel of unpredictable strength. Only the Siemens-Martin open-hearth process developed by 1875 yielded steel of consistent quality. The steel needed for the bridge was provided by two steel works in Scotland and one in Wales.
At its peak, approximately 4,600 workers were employed in its construction. Initially it was recorded that 57 lives were lost; but extensive research by local historians increases that toll to 63. Eight men were saved from drowning by boats positioned in the river under the working areas. Hundreds of workers were injured by serious accidents, and one log book of accidents and sickness had 26,000 entries.
Work at the site began at the end of 1882, with the construction at South Queensferry of the extensive workshops where the steelwork was to be fabricated. These eventually occupied more than 50 acres. Work on the foundations of the bridge began in February 1883, and the first of the caissons was launched on 26 May 1884. The bridge was completed in December 1889, and load testing of the completed bridge was carried out on 21 January 1890. Two trains, each consisting of three heavy locomotives and 50 wagons loaded with coal, totalling 1,880 tons in weight, were driven slowly from South Queensferry to the middle of the north cantilever, stopping frequently to measure the deflection of the bridge. This represented more than twice the design load of the bridge: the deflection under load was as expected. A few days previously there had been a violent storm, producing the highest wind pressure recorded to date at Inchgarvie, and the deflection of the cantilevers had been less than 25 mm (1 in). The first complete crossing took place on 24 February, when a train consisting of two carriages carrying the chairmen of the various railway companies involved made several crossings. The bridge was opened on 4 March 1890 by the Prince of Wales, later King Edward VII, who drove home the last rivet, which was gold plated and suitably inscribed. The key for the official opening was made by Edinburgh silversmith John Finlayson Bain, commemorated in a plaque on the bridge.
Race to the North
Before the opening of the Forth Bridge, the railway journey from London to Aberdeen had taken about 13 hours running from Euston and using the London and North Western Railway and Caledonian Railway on a west coast route. With competition opened up along the east coast route from the Great Northern, North Eastern and North British railways and starting from King's Cross, unofficial racing took place between the two consortia, reducing the journey time to about 8½ hours on the overnight runs. This reached a climax in 1895 with sensational daily press reports about the "Race to the North". When race fever subsided the journey times became around 10½ hours.
In the First World War British sailors would time their departures or returns to the base at Rosyth by asking when they would pass under the bridge. This practice continued at least up to the 1990s. In both wars the anchorage at Rosyth extended eastwards beyond the bridge.
The first German air attack on Britain in the Second World War took place over the Forth Bridge, six weeks into the war, on 16 October 1939. Although known as the "Forth Bridge Raid", the bridge was not the target and not damaged. In all, 12 German Junkers Ju 88 bombers led by two reconnaissance Heinkel He 111s from Westerland on the island of Sylt, 460 miles (400 nmi; 740 km) away, reached the Scottish coast in four waves of three. The target of the attack was shipping from the Rosyth naval base in the Forth, close to the bridge. The Germans were hoping to find HMS Hood, the largest capital ship in the Royal Navy. At this time, the Luftwaffe's rules of engagement restricted action to targets on water and not in the dockyard. Although HMS Repulse was in Rosyth, the attack was concentrated on the cruisers HMS Edinburgh and HMS Southampton, the carrier HMS Furious and the destroyer HMS Jervis. Three ships were damaged in the raid: the destroyer HMS Mohawk and two cruisers, HMS Southampton and HMS Edinburgh. Sixteen Royal Navy crew died and a further 44 were wounded, although this information was not made public at the time. Spitfires from RAF 603 "City of Edinburgh" Squadron intercepted the raiders and during the attack shot down the first German aircraft downed over Britain in the war. One bomber came down in the water off Port Seton on the East Lothian coast, and another off Crail on the coast of Fife. After the war it was learned that a third bomber had come down in Holland as a result of damage inflicted in the raid. Later in the month, a reconnaissance Heinkel 111 crashed near Humbie in East Lothian and photographs of this crashed plane were, and still are, used erroneously to illustrate the raid of 16 October, thus sowing confusion as to whether a third aircraft had been brought down. Members of the bomber crew at Port Seton were rescued and made prisoners-of-war. Two bodies were recovered from the Crail wreckage and, after a full military funeral with firing party, were interred in Portobello cemetery, Edinburgh. The body of the gunner was never found. A propaganda film, "Squadron 992", made by the GPO Film Unit after the raid recreated the raid and conveyed the false impression that the main target was the bridge.
Prior to the opening of the bridge, the North British Railway (NBR) had lines on both sides of the Firth of Forth between which trains could not pass except by running at least as far west as Alloa and using the lines of a rival company. The only alternative route between Edinburgh and Fife involved the ferry at Queensferry, which was purchased by the NBR in 1867. Accordingly, the NBR sponsored the Forth Bridge project which would give them a direct link independent of the Caledonian Railway; a conference at York in 1881 set up the Forth Bridge Railway Committee, to which the NBR contributed 35% of the cost. The remaining money came from three English railways, who ran trains from London over NBR tracks: the Midland Railway, to which the NBR connected at Carlisle and which owned the route to London (St Pancras), contributed 30%, whilst the remainder came equally from the North Eastern Railway and the Great Northern Railway, who between them owned the route between Berwick-upon-Tweed and London (King's Cross), via Doncaster. This body undertook to construct and maintain the bridge. In 1882 the NBR were given powers to purchase the bridge, which it never exercised. At the time of the 1923 Grouping, the bridge was still jointly owned by the same four railways, and so it became jointly owned by these companies' successors, the London Midland and Scottish Railway (30%) and the London and North Eastern Railway (70%). The Forth Bridge Railway Company was named in the Transport Act 1947 as one of the bodies to be nationalised and so became part of British Railways on 1 January 1948. Under the Act, Forth Bridge shareholders would receive £109 of British Transport stock for each £100 of Forth Bridge Debenture stock; and £104-17-6d (£104.87½) of British Transport stock for each £100 of Forth Bridge Ordinary stock.
Visitors centre plans
Network Rail is in the early planning stages to add a visitor centre to the bridge, which would include a viewing platform on top of the North Queensferry side, or a bridge climbing experience to the South Queensferry side.
The bridge has a speed limit of 50 miles per hour (80 km/h) for high-speed trains and diesel multiple units, 40 miles per hour (64 km/h) for ordinary passenger trains and 30 miles per hour (48 km/h) for freight trains. The route availability code is RA8, but freight trains above a certain size must not pass each other on the bridge.
Up to 190–200 trains per day crossed the bridge in 2006. The Forth Bridge needs constant maintenance and the ancillary works for the bridge include not only a maintenance workshop and yard but a railway "colony" of some fifty houses at Dalmeny Station. The track on the bridge is of "waybeam" construction: 12 inch square baulks of timber 6 metres long are bolted into steel troughs in the bridge deck and the rails are fixed on top of these sleepers. Prior to 1992 the rails on the bridge were of a unique "Forth Bridge" section.
"Painting the Forth Bridge" is a colloquial expression for a never-ending task, coined on the erroneous belief that at one time in the history of the bridge repainting was required and commenced immediately upon completion of the previous repaint. Such a practice never existed, as weathered area were given more attention, there was a permanent maintenance crew.
Floodlighting was installed in 1991, and the track was renewed between 1992 and 1995. The bridge was costing British Rail GB£1 million a year to maintain, and they announced that the schedule of painting would be interrupted to save money, and the following year, upon privatisation, Railtrack took over. A GB£40 mllion package of works commenced in 1998, and in 2002 the responsibility of the bridge was passed to Network Rail.
Work started in 2002 to fully repaint the bridge for the first time in its history, in a GB£130 million contract awarded to Balfour Beatty. Up to 4,000 tonnes (3,900 long tons; 4,400 short tons) of scaffolding was on the bridge at any time, and computer modelling was used to analyse the additional wind load on the structure. The bridge was encapsulated in a climate controlled membrane to give the proper conditions for the application of the paint. All previous layers of paint were removed using copper slag fired at up to 200 miles per hour (320 km/h), exposing the steel and allowing repairs to be made. The paint, developed specifically for the bridge by Leigh Paints, consisted of a system of three coats derived from that used in the North Sea oil industry. 240,000 litres (53,000 imp gal; 63,000 US gal) of paint was applied to 255,000 square metres (2,740,000 sq ft) of the structure, and it is not expected to need repainting for at at least 20 years. The top coat can be reapplied indefinitely, minimising future maintenance work.
In a report produced by JE Jacobs, Grant Thornton and Faber Maunsell in 2007 which reviewed the alternative options for a second road crossing, it was stated that "Network Rail has estimated the life of the bridge to be in excess of 100 years. However, this is dependant [sic] upon NR’s inspection and refurbishment works programme for the bridge being carried out year on year".
In 2014 Clydesdale Bank announced the introduction of Britain's second polymer banknote, a £5 note featuring Sir William Arrol and the Forth Bridge (the first was issued by Northern Bank in 2000). It will be introduced in 2015 to commemorate the 125th anniversary of the opening of the bridge, and its nomination to become a UNESCO World Heritage Site.
- There is a scene on the bridge in Alfred Hitchcock's 1935 film The 39 Steps and it is featured even more prominently in the 1959 remake of the film.
- The bridge featured in posters advertising the soft drink Barr's Irn-Bru, with the slogan: Made in Scotland, from girders
- The bridge was lit up red for BBC's Comic Relief in 2005.
- A countdown clock to the millennium was placed on the bridge in 1998.
- The Bridge, a novel by Iain Banks, is mainly set on a fictionalised version of the bridge.
- In Alan Turing's most famous paper about artificial intelligence, one of the challenges put to the subject of an imagined Turing test is "Please write me a sonnet on the subject of the Forth Bridge". The test subject in Turing's paper answers, "Count me out on this one. I never could write poetry".
- Sébastien Foucan, a French freerunner, crawled along one of the highest points of the bridge, without a harness, for the Jump Britain documentary made by Channel 4.
- The bridge is included in the video game Grand Theft Auto: San Andreas by Edinburgh-based developer Rockstar North. Renamed the Kincaid Bridge, it serves as the main railway bridge of the fictional city of San Fierro, and appears alongside a virtual Forth Road Bridge.
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- Summerhayes, Stuart (2010). Design Risk Management. John Wiley & Sons. ISBN 9781444318906.
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|Wikimedia Commons has media related to Forth bridges.|
- 40 black-and-white photographs of the construction of the Forth Bridge taken from 1886–1887 by Philip Phillips at National Library of Scotland
- Forth Bridges Visitor Centre Trust - Rail Bridge Main
- Forth Bridge Memorial
- Forth Rail Bridge at Structurae
- Scottish Poetry Library: Poetry Map of Scotland (Firth of Forth): The Construction of the Forth Bridge, 1882–1890, by Colin Donati
- Clarence Winchester, ed (1935), "The Forth Bridge", Railway Wonders of the World, pp. 432–441