Forth Bridge (railway)

:For the nearby road bridge, see Forth Road Bridge.

Construction

The bridge is, even today, regarded as an engineering marvel. It is 2.5 km (1.5 miles) in length, and the track is elevated 46 m (approx. 150 ft) above high tide. It consists of two main spans of 1,710 ft, two side spans of 675 ft, 15 approach spans of 168 ft and five of 25 ft. The main spans comprise two 680 feet cantilever arms supporting a central 350 ft span girder bridges. The three great four-tower cantilever structures are 340 ft (104 m) tall, each 70 ft diameter foot resting on separate foundations. The southern group of foundations had to be constructed as caissons under compressed air, to a depth of 90 ft. 57 lives were lost during construction; more than 51,000 tons of steel were used, as well as 18,122 m3 of granite and 8M rivets. The bridge was opened by the Prince of Wales, later King Edward VII, who drove home the last rivet, which was gold plated and suitably inscribed. A contemporary materials analysis of the bridge, circa 2002, found that the steel in the bridge is of good quality, with little variation.

Related Topics:
Engineering - Cantilever - Caisson - Granite - Edward VII

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The use of a cantilever in bridge design was not a new idea, but the scale of Baker's undertaking was a real pioneering effort, afterwards extensively followed in different parts of the world. Much of the work done was without precedent, including calculations for incidence of erection stresses, provisions made for reducing future maintenance costs, calculations for wind pressures made evident by the Tay Bridge disaster, the effect of temperature stresses on the structure, and so on.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~