Forth Rail BridgeCopyright: ramonespelt 123rf.com

Forth Rail Bridge

This iconic structure began life in 1882 after the catastrophic collapse of the Tay Bridge. Many lessons were learnt and applied to the Forth which is strong enough to take even the heaviest freight trains. Unlike Bouch, earlier, John Fowler and Benjamin Baker did listen to all of the advice and designed the bridge to take a minimum wind load of 273.4 kgf/m2 (52 pounds per foot).

Forth Rail planCopyright: Network Rail Corporate Archive

At the time of construction, the Forth was a major UK construction project, the first major steel structure using 258 million kg (258,000 tonnes) of masonry and 53 million kg (53,000 tonnes) of steel. Tolerances for heat expansion and contraction to 420mm movement across the entire 1,630 m central section. The entire structure contains 6.5 million rivets!

Forth under constructionPublic Domain Wikimedia Commons National Library of Scotland

The construction period was relatively cool and the workers had to wait for the temperature to warm up sufficiently before they could put the final rivets in. The structure needed to expand to specific calculations.

From the moment the bridge was opened it has been a tourist attraction with visitors from all over the world.

During 1894 the bridge carried a massive weight of nearly 75 million kg (7.5 million tonnes) in the form of 26,451 passenger trains, 18,777 goods trains and 2,678 lighter engines. In 2000 a total of 105 million kg (10.5 million tonnes) crossed with 54,080 passenger trains and 6,240 freight trains.

So iconic is the bridge that it features in Alfred Hitchcock's classic 'The 39 Steps' and again in the 1959 remake. The bridge found its way onto the 2004 issue of the £1.00 coin and in the design of the Scottish £20.00 note. Did you also know that the Forth Rail Bridge has appeared in the renamed version of Grand Theft Auto and was also the inspiration for a bridge in a Pokémon game?

In 2002 a major restoration and refurbishment began which lasted for 10 years at a cost of £130 million. 40,000kg (4,000 tonnes) of scaffolding was used and a total of 4.5 million man-hours were spent on the project. At its peak there were 400 different tradesmen involved.

There is a myth that once you finish painting the bridge you need to start from the beginning once again. The 2002 restoration was the first time that it was completely painted, from one end to the other. The 230,000m2 steel structure was first sandblasted to remove old paint and bird droppings. The exposed steel was then sprayed with a specially designed three-part coating system that was originally used in the North Sea oil industry. The top coat of pain was mixed to 'Forth Bridge Red' to match the original red oxide colour used in 1890. To complete the painting it required 240,000 litres of paint which cost approximately £370 per m2!

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