Bouch ' s proposed bridge in 1871
Works started in 1878 with the construction of one of the piers . But once again circumstances were against this challenge . After the Tay Bridge collapsed in 1879 works were stopped almost immediately . The public inquiry into the disaster , chaired by Henry Cadogan Rothery , found the Tay Bridge to be " badly designed , badly constructed and badly maintained ," with Bouch being " mainly to blame " for the defects in construction and maintenance and " entirely responsible " for the defects in design . Bouch ' s design of the Forth Bridge was formally abandoned on 13 January 1881 , and Sir John Fowler , W . H . Barlow and T . E . Harrison were invited to give proposals for a bridge . One of the piers of from the abandoned works for Bouch ’ s bridge remains to this day as the base of a lighthouse .
Design The new design was made on the principle of the cantilever truss bridge , where a cantilever beam supports a light central girder , The Bridge is 2,467m long , and the double track is elevated 45.72m above the water level at high tide . It consists of two main spans of 518.16m , two side spans of 207.3m , and 15 approach spans of 51.2m . Each main span consists of two 207.3m cantilever arms supporting a central 106.7m span truss . The weight of the bridge superstructure was 51,324 t , including the 6.5 million rivets used . The three great four-tower cantilever structures are 110.03m tall , each tower resting on a separate pier . These were constructed using 21m diameter caissons . The bridge was the first major structure in Britain to be constructed of steel instead of wrought iron .
The original and final design of the bridge
1 / 2017