Peter Paulík , Slovak Technical University
FORTH RAILWAY BRIDGE
Peter Paulík , Slovak Technical University
Photo Credit : Dan Crocker of DC Structures Studio ( NZ )
The bridge spans the Forth between the villages of South Queensferry and North Queensferry and has a total length of 2,467m . It was the longest single cantilever bridge span in the world until 1917 when the Quebec Bridge in Canada was completed . It continues to be the world ' s second-longest single cantilever span .
Prior to the construction of the bridge , ferry boats were the only method available to cross the Firth . The first proposal to build a bridge came in 1818 by James Anderson . Anderson proposed to build a three-span suspension bridge with a design which needed approximately 2,500 tons of iron . Wilhelm Westhofen in 1890 in his book “ The Forth Bridge ” commented on this proposal with sarcasm " 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 .”
Even with the next attempt to design a bridge across the Forth it proved difficult to engineer a suspension bridge which would be able to carry railway traffic . For this reason , engineer Thomas Bouch decided to change the location for the bridge and in 1863 he started work on the design of a single-track girder bridge crossing the Forth near Charlestown , where the river is around two miles wide , but mostly relatively shallow . However by mid-1867 the North British Railway was nearly bankrupt , and all work on the project was stopped .
With the takeover of the ferry service between North and South Queensferry by the North British Railway Company in 1867 and the construction of a connecting line from Ratho , west of Edinburgh , in 1868 , interest in the provision of a fixed link across the Forth increased again . In 1871 , Bouch proposed a stiffened steel suspension bridge at the site of the present rail bridge .
1 / 2017