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90-511: The Forth Bridge is a cantilever railway bridge across the Firth of Forth in the east of Scotland , 9 miles (14 kilometres) west of central Edinburgh . Completed in 1890, it is considered a symbol of Scotland (having been voted Scotland's greatest man-made wonder in 2016), and is a UNESCO World Heritage Site . It was designed by English engineers Sir John Fowler and Sir Benjamin Baker . It

180-513: A barge, formerly called the Hougoumont that was moored off South Queensferry. For a time a paddle steamer was hired for the movement of workers, but after a time it was replaced with one capable of carrying 450 men, and the barges were also used for carrying people. Special trains were run from Edinburgh and Dunfermline, and a steamer ran to Leith in the summer. The three towers of the cantilever are each seated on four circular piers. Since

270-612: A cantilever bridge. The Forth Bridge is a notable example of an early cantilever bridge. This bridge held the record for longest span in the world for twenty-nine years until it was surpassed by the Quebec Bridge . The engineers responsible for the bridge, Sir Benjamin Baker and Sir John Fowler , demonstrated the structural principles of the suspended span cantilever by sitting in chairs and supporting their colleague, Kaichi Watanabe , in between them, using just their arms and wooden poles. The suspended span, where Watanabe sits,

360-422: A fire in a bothy , 1 of caisson disease , and the cause of five deaths is unknown. The Sick and Accident Club was founded in 1883, and membership was compulsory for all contractors' employees. It would provide medical treatment to men and sometimes their families, and pay them if they were unable to work. The club also paid for funerals within certain limits, and would provide grants to the widows of men killed or

450-490: A gas furnace, and then pressed into the correct curve. The curved plates were then assembled on a mandrel , and holes drilled for rivets, before they were marked individually and moved to the correct location to be added to the structure. Lattice members and other parts were also assembled at South Queensferry, using cranes and highly efficient hydraulic rivetters. The bridge was completed in December 1889, and load testing of

540-507: A hinge in the girder. Heinrich Gerber was one of the engineers to obtain a patent for a hinged girder (1866) and is recognized as the first to build one. The Hassfurt Bridge over the Main river in Germany with a central span of 124 feet (38 metres) was completed in 1867 and is recognized as the first modern cantilever bridge. The High Bridge of Kentucky by C. Shaler Smith (1877),

630-449: A landing stage at Inchgarvie commenced. Extant buildings, including fortifications built in the 15th century, were roofed over to increase the available space, and the rock at the west of the island was cut down to a level seven feet (2.1 m) above high water, and a seawall was built to protect against large waves. In 1884 a compulsory purchase order was obtained for the island, as it was found that previously available area enclosed by

720-436: A large extent before being floated to their final resting-places. The first caisson, for the south-west pier at South Queensferry was launched on 26 May 1884, and the last caisson was launched on 29 May 1885 for the south-west pier at Inchgarvie. When the caissons had been launched and moored, they were extended upwards with a temporary portion in order to keep water out and allow the granite pier to be built when in place. Above

810-491: A pin, usually after forcing the union point apart, and when jacks are removed and the bridge decking is added the bridge becomes a truss arch bridge . Such unsupported construction is only possible where appropriate rock is available to support the tension in the upper chord of the span during construction, usually limiting this method to the spanning of narrow canyons. World's longest cantilever bridges (by longest span): Pig iron Pig iron , also known as crude iron ,

900-476: A practice never existed, as weathered areas were given more attention, but there was a permanent maintenance crew. Between 2001 and 2011, the bridge was covered in a new coating designed to last for 25 years, bringing an end to having painters as a regular part of the maintenance crew. Colin Hardie, of Balfour Beatty Construction , was reported as saying, Cantilever bridge The steel truss cantilever bridge

990-456: A principle that has been used for thousands of years in the construction of bridges. In order to illustrate the use of tension and compression in the bridge, a demonstration in 1887 had the Japanese engineer Kaichi Watanabe supported between Fowler and Baker sitting in chairs. Fowler and Baker represent the cantilevers, with their arms in tension and the sticks under compression, and the bricks

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1080-642: A rail link from Ratho in 1868, establishing a contiguous link with Fife. Interest in bridging the Forth increased again, and in 1871 Bouch proposed a stiffened steel suspension bridge on roughly the same line as taken by the present rail bridge. This design was examined and pronounced acceptable by W. H. Barlow and William Pole , both "eminent" civil engineers, and Parliament passed in August 1873 an act authorising its construction. Work started in September 1878, in

1170-457: A slope of around 1 in 5, so the rock was prepared with concrete and sandbags to make a landing-spot for the caissons. Excavation was carried out by drilling and blasting , but no blasting was done within 1.5 ft (0.46 m) of the caissons, and the remaining rock was quarried to within 6 in (150 mm). Once the positions of the piers had been established, the first task at the Fife end

1260-462: A total length of 8,094 feet (2,467 m). When it opened it had the longest single cantilever bridge span in the world, until 1919 when the Quebec Bridge in Canada was completed. It continues to be the world's second-longest single cantilever span, with a span of 1,709 feet (521 m). The bridge and its associated railway infrastructure are owned by Network Rail . Before the construction of

1350-469: 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". For the railway age, Thomas Bouch designed for the Edinburgh and Northern Railway a roll-on/roll-off ferry between Granton and Burntisland that opened in 1850, which proved so successful that another was ordered for

1440-466: 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. "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

1530-402: Is a branching structure formed in sand , with many individual ingots at right angles to a central channel or "runner", resembling a litter of piglets being nursed by a sow . When the metal had cooled and hardened, the smaller ingots (the "pigs") were simply broken from the runner (the "sow"), hence the name "pig iron". As pig iron is intended for remelting, the uneven size of the ingots and

1620-434: Is achieved by remelting pig iron, often along with substantial quantities of steel and scrap iron, removing undesirable contaminants, adding alloys, and adjusting the carbon content. Ductile iron can also be produced using certain high purity grades of pig iron; depending on the grade of ductile iron being produced, the pig irons chosen may be low in the elements silicon, manganese, sulfur and phosphorus. High purity pig iron

1710-410: Is an intermediate good used by the iron industry in the production of steel . It is developed by smelting iron ore in a blast furnace . Pig iron has a high carbon content, typically 3.8–4.7 %, along with silica and other dross , which makes it brittle and not useful directly as a material except for limited applications. The traditional shape of the molds used for pig iron ingots

1800-505: Is formed by two cantilever arms extending from opposite sides of an obstacle to be crossed, meeting at the center. In a common variant, the suspended span , the cantilever arms do not meet in the center; instead, they support a central truss bridge which rests on the ends of the cantilever arms. The suspended span may be built off-site and lifted into place, or constructed in place using special travelling supports. A common way to construct steel truss and prestressed concrete cantilever spans

1890-424: Is in the center. The wooden poles resist the compression of the lower chord , while the outstretched arms support the tension of the upper chord. The placement of the brick counterweights demonstrates the action of the outer foundations. Cantilever Bridge.—A structure at least one portion of which acts as an anchorage for sustaining another portion which extends beyond the supporting pier. A simple cantilever span

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1980-598: Is sometimes referred to as the Forth Rail Bridge (to distinguish it from the adjacent Forth Road Bridge ), although this is not its official name. Construction of the bridge began in 1882 and it was opened on 4 March 1890 by the Duke of Rothesay , the future Edward VII . The bridge carries the Edinburgh–Aberdeen line across the Forth between the villages of South Queensferry and North Queensferry and has

2070-405: Is to counterbalance each cantilever arm with another cantilever arm projecting the opposite direction, forming a balanced cantilever ; when they attach to a solid foundation, the counterbalancing arms are called anchor arms . Thus, in a bridge built on two foundation piers, there are four cantilever arms: two which span the obstacle, and two anchor arms that extend away from the obstacle. Because of

2160-528: Is used to dilute any elements in a ductile iron charge which may be harmful to the ductile iron process (except carbon). Pig iron was historically poured directly out of the bottom of the blast furnace through a trough into a ladle car for transfer to the steel mill in mostly liquid form; in this state, the pig iron was referred to as hot metal . The hot metal was then poured into a steelmaking vessel to produce steel , typically an electric arc furnace , induction furnace or basic oxygen furnace , where

2250-572: The London and North Western Railway and Caledonian Railway on a west coast route . With competition opened 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 8 1 ⁄ 2 hours on the overnight runs. This reached a climax in 1895 with sensational daily press reports about

2340-547: The Niagara Cantilever Bridge by Charles Conrad Schneider (1883) and the Poughkeepsie Bridge by John Francis O'Rourke and Pomeroy P. Dickinson (1889) were all important early uses of the cantilever design. The Kentucky River Bridge spanned a gorge that was 275 feet (84 metres) deep and took full advantage of the fact that falsework, or temporary support, is not needed for the main span of

2430-551: 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

2520-619: The " Race to the North ". When race fever subsided the journey times became around 10 1 ⁄ 2 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. 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

2610-513: 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, about 2 miles (3.2 km) to

2700-673: The Act, Forth Bridge shareholders would receive £109 of British Transport stock for each £100 of Forth Bridge Debenture stock; and £104 17 s  6 d of British Transport stock for each £100 of Forth Bridge Ordinary stock. As of April 2017, the bridge and its associated railway infrastructure were owned by Network Rail Infrastructure Limited . 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

2790-678: The Chinese ones. Wagner has postulated a possible link via Persian contacts with China along the Silk Road and Viking contacts with Persia, but there is a chronological gap between the Viking period and Lapphyttan. Smelting and producing wrought iron were known in ancient Europe and the Middle East, but it was produced in bloomeries by direct reduction . Small prills of pig iron dispersed in slag are produced in all iron furnaces, but

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2880-467: The Fife end had to be removed to make way for the north-east pier. The rocky shore was levelled to a height of 7 feet (2.1 m) above high water to make way for plant and materials, and huts and other facilities for workmen were set up further inland. The preparations at South Queensferry were much more substantial, and required the steep hillside to be terraced. Wooden huts and shops for the workmen were put up, as well as more substantial brick houses for

2970-526: The Forth Bridge a more deadly structure than the failed Tay Bridge when counting both the 59 known deaths attributed to the Tay Bridge Disaster , that led to the earlier proposal for the Forth Bridge construction being halted and subsequently redesigned, combined with the 14 deaths during its construction. Before the opening of the Forth Bridge, the railway journey from London to Aberdeen had taken about 13 hours running from Euston and using

3060-570: 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, which ran trains from London over NBR tracks. The Midland Railway , which connected to the NBR at Carlisle and which owned

3150-573: The Siemens brothers and improvements by the Martin brothers, the process of manufacture enabled high quality steel to be produced quickly. The new works took possession of offices and stores erected by Arrol in connection with Bouch's bridge; these were expanded considerably over time. Reginald Middleton took an accurate survey to establish the exact position of the bridge and allow the permanent construction work to commence. The old coastguard station at

3240-588: The Tay. In late 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 ,

3330-584: The advice of the Astronomer Royal  – he had assumed a wind loading of only 10 lb/sq ft (49 kg/m). This had been accepted by Barlow and Pole in their 1873 assessment of the design, though they qualified in their report that "[while] we raise no object to Mr. Bouch's system, we do not commit ourselves to an opinion that it is the best possible". Bouch's design was formally abandoned on 13 January 1881, and Sir John Fowler , W. H. Barlow, and T. E. Harrison, consulting engineers to

3420-576: 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 wartime propaganda film, Squadron 992 , made by the GPO Film Unit after the raid, recreated it and conveyed the false impression that

3510-479: The bridge, ferries 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

3600-416: The caisson with water, and when the tide fell but the water did not drain from the caisson, its top-heaviness caused to tilt further. Plates were bolted on by divers to raise the edge of the caisson above water level, and the caisson was reinforced with wooden struts as water was pumped out, but pumping took place too quickly and the water pressure tore a hole between 25 and 30 feet (7.6 and 9.1 m) long. It

3690-629: The cantilever end piers which are weighted with cast iron. The bridge was the first major structure in Britain to be constructed of steel; its French contemporary, the Eiffel Tower , was built of wrought iron . Large amounts of steel became available after the invention of the Bessemer process , patented in 1856. In 1859, the Board of Trade imposed a limit of 77.22  N/mm (5  LTf/in ) for

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3780-465: The centre where they were required. Steel was delivered by train and prepared at the yard at South Queensferry , painted with boiled linseed oil , and was then taken to where it was needed by barge. The cement used was Portland cement manufactured on the Medway . It required to be stored before it was able to be used, and up to 1,200 tonnes (1,200 long tons; 1,300 short tons) of cement could be kept in

3870-608: The coast of Fife. After the War it was learned that a third bomber had come down in the Netherlands as a result of damage inflicted during 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

3960-407: 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

4050-466: The construction of the bridge and its immediate aftermath. It is thought that the figure of 57 deaths excluded those who died working on the approaches to the bridge, as those parts were completed by a subcontractor, as well as those who died after the Sick and Accident Club stopped. Of the 73 recorded deaths, 38 were as a result of falling, 9 of being crushed, 9 drowned, 8 struck by a falling object, 3 died in

4140-503: The cruisers, Southampton and Edinburgh were damaged. Sixteen Royal Navy crew died and 44 were wounded, although this information was not made public at the time. Spitfires from 603 "City of Edinburgh" Squadron RAF 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

4230-468: The defects in design. In particular, Bouch had failed to properly account for the effect that high winds would have on the bridge, and in response to this finding the Board of Trade imposed a requirement that all bridges be designed to accept a lateral wind loading of 56 lb/sq ft (270 kg/m). Bouch's 1871 design for the Forth Bridge fell significantly short of this figure, as – on

4320-636: The design necessitated a further 16,000 tonnes (16,000 long tons; 18,000 short tons), about half of this was supplied by the Steel Company of Scotland Ltd. and half by Dalzell's Iron and Steel Works in Motherwell. About 4,200 tonnes (4,100 long tons; 4,600 short tons) of rivets came from the Clyde Rivet Company of Glasgow. Around three or four thousand tons of steel was scrapped, some of which was used for temporary purposes, resulting in

4410-510: The design of the engineer James Carswell . The supports of the approach viaducts are tapered to prevent the impression of the columns widening as they approach the top, and an evaluation of the aesthetics of the Bridge in 2007, by A. D. Magee of the University of Bath , identified that order was present throughout, and this included in the approach viaducts. Magee points out that the masonry

4500-501: The discrepancy between the quantity delivered and the quantity erected. After Dalmeny railway station , the track curves slightly to the east before coming to the southern approach viaduct. After the railway crosses the bridge, it passes through North Queensferry railway station , before curving to the west, and then back to the east over the Jamestown Viaduct . The approaches were built under separate contract and were to

4590-417: The double track elevated 150 feet (45.72 m) above the water level at high tide. It consists of two main spans of 1,700 feet (518.16 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

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4680-423: The foremen and tenements for leading hands and gangers. Drill roads and workshops were built, as well as a drawing loft 200 by 60 feet (61 by 18 m) to allow full size drawings and templates to be laid out. A cable was also laid across the Forth to allow telephone communication between the centres at South Queensferry, Inchgarvie, and North Queensferry, and girders from the collapsed Tay Bridge were laid across

4770-621: The form of a brick pier at the western end of the mid-Forth island of Inchgarvie . After the 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

4860-541: The foundations each of which is different to suit the different sites, is a tapered circular granite pier with a diameter of 55 feet (17 m) at the bottom and a height of 36 feet (11 m). The rock on which the two northern piers at Inchgarvie are located is submerged at high water, and of the other two piers, the site of the eastern one is about half submerged and the western one was three-quarters submerged. This meant work initially had to be done at low tide. The southern piers on Inchgarvie are sited on solid rock with

4950-427: The foundations were required to be constructed at or below sea level, they were excavated with the assistance of caissons and cofferdams . Caissons were used at locations that were either always under water, even at low tide , or where the foundations were to be built on mud and clay . Cofferdams were used where rock was nearer to the surface, and it was possible to work in low tide. Six caissons were excavated by

5040-563: The four piers of the bridge was insufficient for the storage of materials. Iron staging reinforced wood in heavily used areas was put up over the island, eventually covering around 10,000 square yards (8,400 m) and using over 1,000 tonnes (980 long tons; 1,100 short tons) of iron. The bridge uses 55,000 tonnes (54,000 long tons; 61,000 short tons) of steel and 140,000 cubic yards (110,000 m) of masonry. Many materials, including granite from Aberdeen , Arbroath rubble, sand, timber, and sometimes coke and coal, could be taken straight to

5130-410: The girder or truss and meant that longer spans could be built. Several 19th-century engineers patented continuous bridges with hinge points mid-span. The use of a hinge in the multi-span system presented the advantages of a statically determinate system and of a bridge that could handle differential settlement of the foundations. Engineers could more easily calculate the forces and stresses with

5220-491: The hill under the viaducts, the girders were assembled at different heights, and only joined when they had reached the same level. Lifting was done using large hydraulic rams , and took place in increments of around 3 feet 6 inches (1.07 m) every four days. The tubular members were constructed in the No. 2 workshop further up the hill at South Queensferry. To bend plates into the required shape, they were first heated in

5310-617: The inclusion of small amounts of sand are insignificant issues when compared to the ease of casting and handling. The Chinese were already making pig iron during the later Zhou dynasty (which ended in 256 BC). Furnaces such as Lapphyttan in Sweden may date back as far back as the 12th century; and some in the County of Mark dating back to the 13th century, which is now part of Westphalia , Germany. It remains to be established whether these northern European developments were derived from

5400-415: The main target was the bridge. Before 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,

5490-469: The maximum design stress in railway bridges; this was revised as technology progressed. The original design required 42,000 tonnes (41,000 long tons; 46,000 short tons) for the cantilevers only, of which 12,000 tonnes (12,000 long tons; 13,000 short tons) was to come from Siemens' steel works in Landore , Wales and the remainder from the Steel Company of Scotland's works near Glasgow. When modifications to

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5580-411: The need for more strength at the balanced cantilever's supports, the bridge superstructure often takes the form of towers above the foundation piers. The Commodore Barry Bridge is an example of this type of cantilever bridge. Steel truss cantilevers support loads by tension of the upper members and compression of the lower ones. Commonly, the structure distributes the tension via the anchor arms to

5670-528: The operator of a bloomery had to avoid conditions causing the phase transition of the iron into liquid in the furnace, as the prill globules or any resulting pig iron are not malleable so can't be hammered in a single piece. Alternatively, decarburizing the pig iron into steel was an extremely tedious process using medieval technology, so in Europe before the Middle Ages the prills were discarded with

5760-609: The outermost supports, while the compression is carried to the foundations beneath the central towers. Many truss cantilever bridges use pinned joints and are therefore statically determinate with no members carrying mixed loads. Prestressed concrete balanced cantilever bridges are often built using segmental construction . Some steel arch bridges (such as the Navajo Bridge ) are built using pure cantilever spans from each side, with neither falsework below nor temporary supporting towers and cables above. These are then joined with

5850-473: The pneumatic method, and are identical in design except for differences in height. A T shaped jetty was built at the site of the South Queensferry piers, to allow one caisson to be attached to each corner, and when launched the caissons were attached to the jetty and permitted to rise and fall with the tide. Excavation beneath the caissons was generally only carried out at high tide when the caisson

5940-589: The pneumatic process, by the French contractor L. Coisea. This process used a positive air pressure inside a sealed caisson to allow dry working conditions at depths of up to 89 feet (27 m). These caissons were constructed and assembled in Glasgow by the Arrol Brothers, namesakes of but unconnected to W. Arrol, before being dismantled and transported to South Queensferry. The caissons were then built up to

6030-433: The project, were invited to propose new designs. Bouch's Inchgarvie pier was left in place, protruding approximately 7 ft (2 m) from the water at high tide. It lies directly under the present bridge and was equipped with a small navigational light c.  1887 . The bridge spans the Forth between the villages of South Queensferry and North Queensferry and has a total length of 8,094 feet (2,467 m) with

6120-425: The railway to the west in order to allow access to the ground there. Near the shore a sawmill and cement store were erected, and a substantial jetty around 2,100 feet (640 m) long was started early in 1883, and extended as necessary, and sidings were built to bring railway vehicles among the shops, and cranes set up to allow the loading and movement of material delivered by rail. In April 1883, construction of

6210-549: The route to London St Pancras , contributed 30%, and 17.5% came equally from each of the North Eastern Railway and the Great Northern Railway , which 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

6300-511: The slag. Traditionally, pig iron was worked into wrought iron in finery forges , later puddling furnaces , and more recently, into steel . In these processes, pig iron is melted and a strong current of air is directed over it while it is stirred or agitated. This causes the dissolved impurities (such as silicon) to be thoroughly oxidized. An intermediate product of puddling is known as refined pig iron , finers metal , or refined iron . Pig iron can also be used to produce gray iron . This

6390-412: The small uninhabited island of Inchgarvie acted as cofferdams , 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. The bridge is built on the principle of the cantilever bridge , where a cantilever beam supports a light central girder,

6480-557: 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

6570-411: 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 m × 18.3 m × 2.1 m) (the original design called for a 114 by 80 by 9 feet (34.7 m × 24.4 m × 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

6660-534: The west of the bridge. The Germans were hoping to find HMS  Hood , the largest capital ship in the Royal Navy. Luftwaffe 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 Edinburgh and Southampton , the carrier Furious and the destroyer Jervis . The destroyer Mohawk and

6750-531: The wives of those permanently disabled. Eight men were saved from drowning by rowing boats positioned in the river under the working areas. In 2019, it was reported that historians of the Queensferry Historian Group had discovered that at least 21 more men died building the Forth Bridge than was previously thought, in an alleged "cover up" of the true human cost of the structure, taking the new death toll to 78. Tragically, this arguably makes

6840-404: 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

6930-403: 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 m) of granite . The three great four-tower cantilever structures are 361 feet (110.03 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

7020-428: Was a self-made man , who had been apprenticed to a blacksmith at the age of thirteen before going on to have a highly successful business. Tancred was a professional engineer who had worked with Arrol before, but he would leave the partnership during the course of construction. The steel was produced by Frederick and William Siemens (England) and Pierre and Emile Martin (France). Following advances in furnace design by

7110-409: Was a major engineering breakthrough when first put into practice, as it can span distances of over 1,500 feet (450 m), and can be more easily constructed at difficult crossings by virtue of using little or no falsework . Engineers in the 19th century understood that a bridge that was continuous across multiple supports would distribute the loads among them. This would result in lower stresses in

7200-406: 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 railway companies involved made several crossings. The bridge

7290-424: Was carefully planned, and has neat block work even in areas not immediately visible from the ground. The Bill for the construction of the bridge was passed on 19 May 1882 after an eight-day enquiry, the only objections being from rival railway companies. On 21 December, the contract was let to Sir Thomas Tancred, T. H. Falkiner and Joseph Philips, civil engineers and contractor, and Sir William Arrol & Co. Arrol

7380-437: Was completed. It continues to be the world's second-longest single cantilever span, with a span of 1,709 feet (521 m). To make the fullest use of the bridge, several new railway connections were built, bringing main line routes to the bridge. The construction of some of these lines was only completed on 2 June 1890, delaying the implementation of a full express train service over the bridge until that date. Even then, there

7470-568: Was considerable congestion at Edinburgh Waverley station with remarshalling of the portions of the new, more intensive train service. At its peak, approximately 4,600 workers were employed in the bridge's construction. Wilhelm Westhofen recorded in 1890 that 57 people died. In 2005 the Forth Bridge Memorial Committee was set up to erect a monument to those lost, and a team of local historians set out to name all those who died. As of 2009, 73 deaths have been connected with

7560-409: Was decided to build them at a lower level and then raise them in tandem with the construction of the masonry piers. The two viaducts have fifteen spans between them, each one 168 feet (51 m) long and weighing slightly over 200 tonnes (200 long tons; 220 short tons). Two spans are attached together to make a continuous girder , with an expansion joint between each pair of spans. Due to the slope of

7650-425: Was decided to construct a "barrel" of large timbers inside the caisson to reinforce it, and it was ten months before the caisson could be pumped out and dug free. The caisson was refloated on 19 October 1885, and then moved into position and sunk with suitable modifications. The approach viaducts to the north and south had to be carried at 130 feet 6 inches (39.78 m) above the level of high water, and it

7740-429: Was in 1863–1864 working on a single-track girder bridge crossing the Forth near Charlestown , where the river is around 2 miles (3.2 km) 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 rock, but Bouch conducted experiments to demonstrate that it

7830-459: Was opened on 4 March 1890 by the Duke of Rothesay, 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. When it opened it had the longest single cantilever bridge span in the world, until 1919 when the Quebec Bridge in Canada

7920-409: Was possible for the silt to support considerable weight. Experiments in late 1864 with weighted caissons achieved a pressure of 5 t/sq ft (4.9 long ton/sq ft; 5.5 short ton/sq ft) on the silt, encouraging Bouch to continue with the design. In August 1865, Richard Hodgson, chairman of the NBR, proposed that the company invest £18,000 to try a different kind of foundation, as

8010-416: Was supported by buoyancy, and then when the tide fell the air pressure was reduced in order to allow the caisson to sink down, and digging would begin anew. The north-west caisson was towed into place in December 1884, but an exceptionally low tide on New Year's Day 1885 caused the caisson to sink into the mud of the river bed and adopt a slight tilt. When the tide rose, it flooded over the lower edge, filling

8100-428: Was to level the site of the northernmost piers, a bedrock of whinstone rising to a level of 10 to 20 feet (3.0 to 6.1 m) above high water, to a height of 7 feet (2.1 m) above high water. The south piers at North Queensferry are sited on rock sloping into the sea, and the site was prepared by diamond drilling holes for explosive charges and blasting the rock. The four South Queensferry caissons were all sunk by

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