Forth Rail Bridge

The Forth Rail Bridge:
Background & First Proposal

History of the Forth Crossing

Prior to the construction of the bridge, ferry boats were the only means to cross the Firth. In 1806, a tunnel was proposed by the Engineer William Vazie (b.1756) running from Rosyth to Queensferry. This was based on geological information derived from underwater mines at Whitehaven in Cumbria. Funding and support could not be raised however, so the project went no further.
In 1818 James Anderson produced a design for a three-span suspension bridge close to the site of the present one.

PaSoaBoChains

Detail from “Plans and sections for a bridge of chains proposed over the Firth of Forth at “Queensferry”, James Anderson, 1818.

Calling for approximately 2,500 tonnes 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.”
Westhoven would become a principal Engineer on the 1890 Rail Bridge, and in feb 1890 would publish the most comprehensive book on the bridges construction.

 

Sir Thomas Bouch

Sir Thomas Bouch

 

 

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 ×2.1m) (the original design called for a 114 by 80 by 9 feet (34.7 ×24.4 ×2.7m) platform of green beech) weighed down with 10,000 tonnes 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.

Bouch Forth Bridge detail

Bouch Forth Bridge detail

Bouch original design.

Design proposals

Bouch’s proposed bridge (Top left, — with detail on the right) along with other proposals on the same principle.
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 making the analysis 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 Forth Rail Bridge:
The Designers, engineers and construction.

The Bridge Builders

Three men stand out in the creation of the Forth Bridge: Designer Benjamin Baker, Consulting Engineer John Fowler and Building Contractor William Arrol.

The Designer

Benjamin Baker

Sir Benjamin Baker

Benjamin Baker (1840-1907) began his career at 16 as an apprentice in the South Wales Ironworks. He moved to London, where he was involved in the construction of Victoria Station, and joined the firm of John Fowler in 1862, becoming a partner in 1875.

The two men were greatly involved in the creation of London’s underground railway system, which had been begun by Fowler in the early 1860s.

Baker’s other achievements included designing the vessel to carry Cleopatra’s Needle from Egypt to Britain, and acting as consulting engineer on the Aswan Dam from 1894 to 1902.

Benjamin Baker was knighted in 1890 for his work on the Forth Bridge.

The following illustration famously shows the principal behind the cantilever design.

Human Cantilever

Picture courtesy of National Records of Scotland Ref: NRS BR/FOR/4/34/161, The human cantilever: three men positioned to model the cantilever principle, 1887 (AAA01407).

and, —— A more up to date take on the human cantilever system !

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The Consulting Engineer

Sir John Fowler
Sir John Fowler

Sir John Fowler (1817-1998) was one of the great civil engineers of the Victorian railway boom. He designed a number of bridges – including the Grosvenor Bridge, which carried the first railway across the Thames – and designed Victoria Station in London and stations in Glasgow, Sheffield, Liverpool and Manchester. Manchester Central Station’s 64m-wide train shed roof was the second widest unsupported steel arch in the country, after the roof of St Pancras Station.

Some of his most memorable work, though, was as a pioneering engineer on the various lines which became the London Underground.
He was also involved in engineering and railway work abroad, with projects in Algeria, Egypt, Australia, Belgium, the United States, Germany, France and Portugal.

In 1865 he became the youngest ever president of the Institution of Civil Engineers and was active in leading the development of training for engineers.
By the time he came to his work on the Forth Bridge he had passed much of the design work on to Benjamin Baker, but he remained the senior partner throughout the construction and was made a baronet on completion of the bridge in 1890.

The Contractor

Sir William ArrollWilliam Arrol (1839-1913) was the classic Victorian ideal of the self-made man, rising from humble origins to fame and a knighthood through hard work and ingenuity.

Beginning work in a cotton mill at the tender age of nine, he became a blacksmith’s apprentice at 14.
He joined a Glasgow firm of builders and bridge makers in 1863 and just five years later was able to launch his own business on his life savings of £85.

He established his Dalmarnock Works in 1872 and within three years built his first major bridge, taking the North British Railway across the Clyde at Bothwell.

He won the contract to build Bouch’s planned suspension bridge across the Forth and, when that was halted, he won the contract for the successful Baker and Fowler design.

In a work schedule which didn’t ease with success, he was also the contractor for the new Tay Rail Bridge, and a typical week would see him spend Monday morning at his works at Dalmarnock before going for two days to the Forth, two days to the Tay and one back at Dalmarnock – before getting on the train to London to consult with Fowler and Baker on the Saturday and sometimes the Sunday too.

By the time he was knighted for his work in 1890, he had already started work on London’s Tower Bridge (opened 1894) and future contracts would include the Wear Bridge at Sunderland and the Nile Bridge at Cairo.

William Westhoven F Rail Br

Two of then final designs, showing the accepted version second.

The Forth Rail Bridge:
Construction

Forth Bridge. Elevation and Section (Coloured)

From the Network Rail Corporate Archive

The Forth Bridge was the first major structure in Britain to be constructed of steel (rather than iron) and this was only possible because of an advance in steel manufacture.
Large amounts of steel had become available after the invention of the Bessemer process in 1855 but its strength was unpredictable.

It wasn’t until the development of the Siemens-Martin process in 1875 that steel of consistent quality could be obtained. The steel used was produced by two steelworks in Scotland and one in Wales.

The cantilever design of the bridge was not new – it had been in use for centuries in the east – but the scale of the Forth Bridge was completely unprecedented, as were many of the technical challenges.

With the Tay Bridge disaster fresh in everyone’s mind, the designers and engineers had to consider calculations for wind pressures and the effects of temperature changes, yet they still created what, at the time, was the longest cantilever bridge span in the world and even yet is the second-longest single span cantilever.
Although work on the foundations of the Forth Bridge started in February 1883, work at the site had begun in 1882 with the construction of steel fabrication workshops on the south side of the river.

At the peak of work about 4,600 men were employed on the construction. It was long said that 57 died during the building of the bridge, although recent research by local historians indicated 63 would be a more accurate figure. The number of injuries is unknown, although one log book of accidents and sickness had 26,000 entries, and hundreds of workers were said to have been left crippled by serious accidents.

Efforts were made to look after the welfare of the men, however. Safety boats saved eight men from drowning. Boots and waterproofs were supplied to men working on the foundations, with thick woollen jackets, overalls and waterproof shoes given to those in superstructure work. Shelters and heated dining rooms were provided on-site and both workers and employers contributed to a sickness and accident fund. Wages on the project were also above average for all classes of worker.

During the seven years of construction, work was carried out from almost 100 feet below the surface of the water to over 300 feet above the surface.
The first three years were spent building the granite piers on which the bridge was to be supported. This was done by sinking caissons – great wrought iron cylinders – to the sea bed and pumping them out so that men could work on the floor of the Forth, creating foundations and building up the piers. This was dangerous and unpleasant work and, in two of the caissons the depth was such that water had to be kept out by filling the working chamber at the bottom with compressed air, the men going through air locks to get to their work.

Work on the superstructure got under way in 1886 and the growing structure became a site of wonder as it grew out from the piers, growing first upwards as the towers were completed, and then outwards as the cantilevers stretched out to meet one another, seemingly defying gravity as they did so.

The bridge was completed in December 1889 and the following month it underwent load testing. Two trains, each comprising three locomotives and 50 wagons loaded with coal (weighing in at a total of 1,880 tons for the two – twice the design load of the bridge) were driven slowly out onto the bridge, stopping frequently for measurements to be taken.

In February the first complete crossing of the bridge took place, with a train carrying the chairmen of the various railway companies involved. On March 4, 1890, the Forth railway bridge – known ever as simply The Forth Bridge – was officially opened by the Prince of Wales, later King Edward VII.

 

The Forth Rail Bridge:
The “Briggers”.

The Men Who Built the Forth Bridge

Briggers

 

The Briggers, is the name given to the thousands of men who built the bridge. They were the men who toiled on a daily basis in hazardous conditions, that we would not comprehend today.

Imagine being in a rivet cage hanging from a work platform hundreds of feet above the icy Forth. Teenage rivet boys and sixty year old ex-shipyard workers faced these conditions every day. They faced many hazards, from caisson disease (the bends) working in a pressurised environment, and painter’s colic to simply being in the wrong place when scaffolding collapsed or a hammer dropped from above.

he Briggers reveals the intriguing incidentals of everyday life that make the story much more than the construction of one of the world’s great engineering feats, from the daily commute from Edinburgh by workers’ train and boat to the 200 pints lined up on the bar of the Hawes Inn at the end of a shift. The book tells of Saturday night brawls and Sunday shebeens and of the countless visitors from the Shah of Persia to pleasure steamer trippers.

For the first time the faces of individual Briggers emerge from the shadow of their bridge, thanks to the latest digital technology and the collection, recently acquired by the National Archives of Scotland, of the work of engineer Evelyn Carey, the only person officially allowed to take photographs on the bridge.

Most remarkably of all the book not only demonstrates that, with at least 73 fatalities, the death toll was significantly higher than the ‘official’ record of 57 but identifies the names and what is known of the lives of the men who died. The painstaking research by four local historians to uncover the names was the inspiration for this book. It arose from an apparently simple request from the Forth Bridge Memorial Committee who sought to give the men who died permanent recognition by erecting monuments to them on either side of the Forth.

The-Briggers-3

A search through official records for a list of names drew a blank. The team then spent years of their spare time scouring contemporary newspaper accounts, death certificates and other sources to compile the first-ever list of the names of the individuals who died. During their trawl they amassed the wealth of detail about life and death on the bridge that is the basis for this book.

In 2012, twin memorials were unveiled at North and South Queensferry, by the First Minister Alex Salmond.

The event marked the end of a 10 year restoration project on the rail crossing over the Firth of Forth.
Thousands of “Briggers” have worked building, maintaining and restoring the bridge over its 129 year history.
The stone base of the 7ft bronze monuments is engraved with the words: “To the Briggers, past and present, who built, restored and continue to maintain this iconic structure.”

The Forth Rail Bridge:
Design Information.

The grand fleet passing under the bridge

The grand fleet passing under the bridge

 

The Forth Bridge has three double cantilevers with two 1700ft suspended spans between them, at the time the longest bridge spans in the world. As required by the Admiralty, the rail level is 150ft (46m) above high water. (as shown above).  Each of the towers has four steel tubes 12ft (3.7m) in diameter and reach to a height of 361ft (110m) above high water. Their foundations extend 89ft below this into the river bed, making the total height from foundations to the top of the towers 137 metres. The total length of the bridge, including its approach viaducts is 2,467 metres. The main structure itself measures 1,630 metres portal to portal.

Baker and Fowler’s bridge was the first major construction in Britain to be made from steel; the bridge incorporates 53,000 tonnes of the material. The design of the bridge was very carefully balanced, with allowance being made for a maximum thermal expansion of 16½ inches (420mm) over the 5350ft (1630m) steel central structure. It incorporated 6.5 million rivets, which aggregated 4,200 tons weight alone. It was designed to withstand a wind force of 56lb per square foot.

Building the foundations for the vast towers started with the construction of huge caissons which were built on site and sunk using compressed air. The first of the caissons was floated into position on 26 May 1884. By 1886 all the foundations were in position ready to take the steelwork.

Thanks to the organisation and inventiveness of William Arrol, the bridge was completed in November 1889, just 6 years after work started (although at the time the weather was particularly cold and Arrol had to wait for milder weather conditions before the enormous structure expanded sufficiently for the final rivets to be inserted). Overall the bridge cost £3million to build and employed a workforce of 4,600 men at the height of construction.

The Forth Rail Bridge:
Vital Stats

Design is a cantilever construction

Total Length                            8,094 Ft or 2,467 m,  (1,630 for the main structure).

Maximum Width                   120 ft (37 m) at the piers

Minimum Width                    32 ft (9.8m) mid point between the cantilevers

Maximum Height                  361 ft (110 m) above high water

Longest span                          1,710 ft (520 m) either side of the center cantilever

Clearance over high water   158 ft (48 m), (Dictated by the Admiralty, for naval vessels passing below).

Foundations                           89 ft below high water

Steel used                                54,160 tons, and a total of 6.5 million rivets.

Granite, Stone & Concrete   79,900 Cubic metres in total.

Construction started             1882

Construction finished           1890

The grand opening                 March 4th 1890.

Before more modern health & safety regulations were introduced, this is how the men went about painting the bridge !

Courtesy 0f British Pathe News

As shown in this photograph from about 1995, the job of painting to protect was a necessary and ongoing task.

Bridge corrosion


The never ending maintenance,  but in 2012 the bridge was finally protected for the next 20 years.

The Forth Rail Bridge:
The Opening

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.

After all testing and inspections of the bridge were completed, it was formally opened by the Prince of Wales (later King Edward VII), who drove home a final gold plated rivet, on 4 March 1890. At the same ceremony, he also knighted Benjamin Baker.

FRailB tapestry

Described as the eight wonder of the world, the forth rail bridge is celebrated in this panel from the great tapestry of scotland. In 2017 the tapestry will move to a permanant base in the Scottish borders, opposite the station at Tweedbank.

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