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032 - Forth Bridge

Object Type: Folder
In Folder: Historical Engineering Collection

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032 - Forth Bridge

The first crossing of the Forth by the railway came in 1850 when the Edinburgh, Leith and Granton Railway started the world’s first ‘train ferry’ – a ferry boat specially designed by Thomas Bouch to take railway coaches – between Granton and Burntisland. In August 1873 the North British Railway obtained authority to build a railway bridge across the Firth of Forth and construction of a suspension bridge, also designed by Thomas Bouch, began in 1878. However when Bouch’s original Tay Bridge collapsed during a storm in December 1879, work on his bridge across the Forth stopped immediately pending a full inquiry. Bouch’s suspension bridge plans were abandoned in 1881 and designs for a new bridge were invited by the newly formed Forth Bridge Railway Company which had been established jointly by those railway companies who had most to gain from a railway crossing the Forth: the North British Railway, the Midland Railway and the North Eastern and Great Northern railways. The bridge was to cross the Forth between South Queensferry, now part of Edinburgh and North Queensferry in Fife, making use of the island of Inch Garvie a little way from the north shore. Its design had to conform to specifications from both the admiralty who stipulated that the Forth remained a navigable channel, and the Board of Trade, concerned by the recent Tay Bridge disaster, who stipulated that the bridge must be rigid and stiff and capable of carrying the heaviest freight trains. John Fowler and his partner Benjamin Baker were engaged by the Forth Bridge Company to develop their cantilevered design for the bridge which took into account these restrictions. The contract for its construction was let to Messers Arrol & Co of Glasgow in 1882 and work on the bridge started in 1883. 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. 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 £3m to build and employed a workforce of 4,600 men at the height of construction. 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. In 2001 a major refurbishment project on the Forth Bridge was announced. Over the following 10 years, sections of the bridge were covered with significant scaffold access systems with specially prepared screening to prevent debris from the sandblasting and paint affecting or contaminating the environment. After removing the old paint back to the metal, any steelwork that required maintenance was repaired before the new paint was applied. After thorough cleaning of the steel structure, paint was then applied in three protective layers, both by airless spray and by hand in areas particularly difficult to access, over an area of 230,000 square metres. The techniques and paint used during the refurbishment means that the bridge will not require a full paint for at least 20 years, finally putting an end to the myth that ‘painting the Forth Bridge’ is a never-ending task.

Network Rail Corporate Archive

Level of Description: Series

Reference Code: NRCA110040 - NRCA163344

Title: The Forth Bridge

Extent and Medium: 121 drawings

Creator: Forth Bridge Railway

Date: 1882-1889

Scope and Content: 121 Drawings showing various engineering elements of the Forth Bridge before and during construction.

Contract Number: n/a

Drawing Number: n/a

Drawing Office Number: n/a

Keywords (Person): Forth Bridge Railway

Keywords (Country): Scotland

Keywords (Structure Name): Forth Bridge

Keywords (Structure Type): Bridge or Viaduct

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Title

Description

Date

Forth Bridge – Bottom Base Plates of Fife NW Pier

3 drawings on one sheet showing Bottom Base Plates of Fife NW Pier

1882-1889

Forth Bridge Railway – Forth Bridge Diagram of Wind Surfaces

Four drawings showing the area of the Forth Bridge that is affected by the force of the wind.

1882-1889

Forth Bridge – Bottom Base Plate for Fife NW Pier

6 drawings showing Bottom Base Plate for Fife NW Pier

14 July 1883

Forth Bridge – Free Cantilever Bay 1 Junction of Vertical Tie and Bottom Member with Alterations

1 drawing showing free cantilever bay 1 junction of vertical tie and bottom member with alterations dated 1886

05 December 1885

Forth Bridge – Bottom Base Plates for Fife NW Pier Fourth Course

3 drawings on one sheet showing Bottom Base Plates for Fife NW Pier Fourth Course

1882-1889

Forth Bridge – A Section of the Vertical Tubes

1 drawing showing a section of the vertical tubes

1882-1889

Forth Bridge Railway line plan

Route plan for the line between Inverkeithing and Dalmeny Station, with incline and radius data

Undated, c.1881

Forth Bridge – Lifting Cage & Supports for Viaduct Approach

1 drawing showing lifting cage & supports for viaduct approach

1882-1889

Forth Bridge – Long Angles for FNE and QSW and FNW and QSE Bedplates

5 drawings on one sheet showing Long Angles for FNE and QSW and FNW and QSE Bedplates

1882-1889

Forth Bridge – The greatest stresses under wind pressure of 56lbs per square foot and under rolling load of 2 tons per foot

1 drawing showing the greatest stresses under wind pressure of 56lbs per square foot and under rolling load of 2 tons per foot run on cantilevers and girders

17 May 1883

Forth Bridge – 2nd Bay of Windbracing Between Struts No.1 Springing from the NW and SE Struts

Five drawings showing 2nd Bay of Windbracing Between Struts No.1 Springing from the NW and SE Struts

1880-1890

Forth Bridge – Sectional plans of Fife north cantilever junction of tie no.1 and strut no.2 with bottom member

1 drawing showing sectional plans of Fife north cantilever junction of tie no.1 and strut no.2 with bottom member

11 September 1884

Forth Bridge – Elevations and sections of Tie 5 Free Cantilever

1 drawing showing elevations and sections of Tie 5 Free Cantilever

August 1887

Forth Bridge Cantilever End Pier

1 drawing of the cantilever end pier showing sections and anchor plates

1882-1890

Forth Bridge Railway – Forth Bridge Diagram showing the Effect of Wind Pressure on Inch-Garvie Pier

20 drawings altogether on 1 sheet. 8 small drawings showing cross sections of piers without train with different pressures, 4 drawings showing the plans of the superstructure with wind pressure on different sections of structure, and 8 drawings showing cross sections of piers with test load of 2 tons per running foot on whole bridge

November 1882

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032 - Forth Bridge

Forth Bridge – Bottom Base Plates of Fife NW Pier

Forth Bridge Railway – Forth Bridge Diagram of Wind Surfaces

Forth Bridge – Bottom Base Plate for Fife NW Pier

Forth Bridge – Free Cantilever Bay 1 Junction of Vertical Tie and Bottom Member with Alterations

Forth Bridge – Bottom Base Plates for Fife NW Pier Fourth Course

Forth Bridge – A Section of the Vertical Tubes

Forth Bridge Railway line plan

Forth Bridge – Lifting Cage & Supports for Viaduct Approach

Forth Bridge – Long Angles for FNE and QSW and FNW and QSE Bedplates

Forth Bridge – The greatest stresses under wind pressure of 56lbs per square foot and under rolling load of 2 tons per foot

Forth Bridge – 2nd Bay of Windbracing Between Struts No.1 Springing from the NW and SE Struts

Forth Bridge – Sectional plans of Fife north cantilever junction of tie no.1 and strut no.2 with bottom member

Forth Bridge – Elevations and sections of Tie 5 Free Cantilever

Forth Bridge Cantilever End Pier

Forth Bridge Railway – Forth Bridge Diagram showing the Effect of Wind Pressure on Inch-Garvie Pier

Forth Bridge – Sections and elevations of bay no.2 vertical tie

Forth Bridge – Diagonal Bracing Between Vertical Ties at Centre of Bay No.1

Forth Bridge – Wind Bracing of Bottom Member Bay 4 Lower Portion Fixed Cantilever