The Forth Bridge

• Official Name: The Forth Bridge
• Location: Firth of Forth, Scotland
• Type: Cultural
• Year of Inscription: 2015

The Forth Bridge is a nineteenth-century railroad bridge that crosses the Firth of Forth between Fife and Edinburgh in eastern Scotland. When the unadorned cantilevered metal structure was completed in 1890, it provided continuous rail service along Scotland’s east coast, allowing passenger and cargo travel from London, England, to Aberdeen, Scotland. The 8,094-foot (2,529-meter) bridge was the first major steel structure built in Britain. It remains in use in the twenty-first century. The bridge is an important Scottish landmark and is featured on many postcards and in books.

Begun in 1884, the bridge’s construction used underwater cylindrical caissons pumped full of air from the surface. This allowed workers to work beneath the firth to construct the granite foundation piers that reach more than 90 feet (27 meters) into the ground under the firth. This foundation was built to support around 54,000 tons of steel, including 6.5 million rivets totaling 4,500 tons in weight. The bridge was designed with three double cantilevers, or structures that connect to their support at only one end. Each double cantilever supports two 1,700-foot (518-meter) suspended spans between it. At the time when it was built, the Forth Bridge was the longest such bridge in the world and remains one of the longest into contemporary times.

From its highest point to the bottom of its foundations, the Forth Bridge measures 450 feet (137 meters). Its rail level is 150 feet (46 meters) above the water level at high tide, a requirement for the firth to remain navigable by larger ships. Its innovative design incorporates four massive hollow tubes of steel, each 12 feet (3.7 meters) in diameter, connected with numerous smaller pieces of steel. The design allows the bridge to support two parallel sets of railroad tracks and withstand wind pressure of 56 pounds per square foot (273.42 kilograms per meter squared). Because of its unique design and large size, it was included on the United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Site list in 2015.

History

Prior to the construction of this bridge, the Firth of Forth posed a barrier to continuous rail travel between Edinburgh and other parts of Scotland and beyond. At the point where the bridge was constructed, the firth is about 121 feet (37 meters) wide. The first attempt to overcome this interruption in the rail lines involved another innovation, the world’s first train ferry. Beginning in 1850, the Edinburgh, Leith, and Granton Railway employed a specially designed ferry boat to transport train cars from one side of the firth to the other, where they could continue on rails.

This was cumbersome. So, in 1873, North British Railway obtained the necessary permission to construct a suspension bridge to cross the firth. British railway engineer Thomas Bouch, who had also designed the ferry, was commissioned to design the bridge. Construction began on that bridge in 1878 but was stopped in 1879 when the Tay Bridge, also designed by Bouch, collapsed during a storm.

Bouch’s plan for the Firth of Forth Bridge was completely abandoned in 1881. Instead, the railway companies of North British, Midland, North Eastern and Great Northern combined to form the Forth Bridge Railway Company. The new company advertised for bridge designs for a structure that would cross the Forth at South Queensferry, which is now in Edinburgh, and North Queensferry in Fife. The design had to meet specifications of the British Navy, which wanted to keep the firth navigable, and the Board of Trade, which had established guidelines to prevent another disaster like the one at the ill-fated Tay Bridge.

English civil engineers John Fowler and Benjamin Baker were tasked with completing the Firth of Forth bridge design. Both men also worked on the designs for the original London Metropolitan underground railway. Scottish contractors Messrs Arrol & Co. were awarded the construction contract in 1882 and began their preliminary work on the bridge in 1883.

Installation of the first underwater caisson began on May 26, 1884. The huge structures were built on site, lowered into the water, and sunk using sandbags and compressed air. After securing them in place, the caissons were kept filled with air pumped in from the surface to allow men to work deep beneath the water. It took about two years to install all the granite underwater piers and foundations before the first steel pieces of the bridge could be installed. The steel for the bridge was provided by Frederick Siemens of England and Pierre and Emile Martin from France. The bridge’s construction also required 27,401 cubic yards (20,950 cubic meters) of granite, 8,868 cubic yards (6,780 cubic meters) of stone, 64,351 cubic yards (49,200 cubic meters) of concrete, and 50 tons of cement.

At the height of the construction project, more than 4,600 men worked on the bridge, which was completed in November of 1889. It took six years to complete, which was considered remarkable as cold weather had forced engineer and bridge builder William Arrol to wait for warmer weather to expand the bridge steel and allow the final rivets to be installed. The cost of the bridge was $15,000,000, which was extremely high at the time.

After a period of inspection and testing, the bridge was formally opened on March 4, 1890. Prince of Wales Edward, who became King Edward VII in 1901, drove in the final golden rivet to complete the structure. The future king also knighted Baker at the same time.

The Forth Bridge remained in continuous use after its construction. In 2001, plans for a major refurbishment were announced. The bridge was encased in a protective scaffolding and screening to safeguard the firth and its shoreline before it was sandblasted to remove old paint and other debris. After inspection and repairs were completed, the bridge received three new coats of a distinctive red paint applied with a special airless sprayer. Hand painting was necessary in a few areas before the application of 275,077 square yards (230,000 square meters) of paint was finished. The protective paint job was completed in 2011 and expected to last twenty to twenty-five years.

Significance

In 2015, the UNESCO World Heritage Convention recognized the historical and architectural importance of the Forth Bridge by including it on the list of World Heritage sites. This designation also protected the land immediately adjacent to the bridge. Inclusion as a World Heritage Site recognizes the historical and societal significance of the bridge, which was the first large-scale steel structure in Great Britain and the largest suspension bridge ever built at the time of its construction.

The bridge remained in the twenty-first century while also remaining virtually unchanged from its initial construction. While the design was structurally significant, it was also simple and unadorned. This uninhibited visibility of its functional architecture adds to the historical and cultural significance of the site.

The Forth Bridge site allows people to see what is generally considered to be an engineering marvel in a setting and appearance that is nearly unchanged from when it opened in 1890. It also recognizes and draws attention to a time when rail travel was of vital importance to the economy of Great Britain and the world. As the first of its kind and still one of the largest steel cantilevered bridges in the world, the Forth Bridge represents a milestone in architectural and engineering accomplishments. The benefits it offered in terms of transportation at the time of its construction along with its continued use for more than twelve decades makes it a significant historical structure worthy of protection and preservation. As a historical structure, the Forth Bridge is listed at Category A, a designation that recognizes its importance and gives it the highest level of statutory protection. Despite great technological advances since its construction, the Forth Bridge remains virtually unchanged, facilitating about two hundred trains per day.

Owned by Network Rail Limited in the twenty-first century, the bridge and its surroundings, including the piers and foundations beneath it and the areas near the bridge’s entrances and exits, is subject to a number of historic designations and protections. The Forth Bridges Forum partnership has been established to ensure that there is continued interest and effort put forth in preserving the structure in the future. The UNESCO World Heritage Site designation also strengthens these efforts.

Bibliography

“The Forth Bridge.” The Forth Bridges, www.theforthbridges.org/forth-bridge. Accessed 7 July 2022.

“The Forth Bridge.” UNESCO World Heritage Convention, whc.unesco.org/en/list/1485/. Accessed 7 July 2022.

“Forth Rail Bridge, Firth of Forth.” Railway Technology, 11 June 2012, www.railway-technology.com/projects/forth-rail-bridge-firth-scotland/. Accessed 7 July 2022.

“The History of the Forth Bridge, Fife.” Network Rail, www.networkrail.co.uk/who-we-are/our-history/iconic-infrastructure/the-history-of-the-forth-bridge-fife/. Accessed 7 July 2022.

Watkins, Jack. “The Forth Bridge: A Masterpiece That’s 1.5 Miles Long, 360ft High, Made of 54,000 Tonnes of Steel and All Set On Granite Piers Sunk 90ft Deep.” Country Life, 21 Nov. 2021, www.countrylife.co.uk/architecture/the-forth-bridge-a-masterpiece-thats-1-5-miles-long-360ft-high-made-of-54000-tonnes-of-steel-and-all-set-on-granite-piers-sunk-90ft-deep-235547. Accessed 7 July 2022.