This was the longest suspension bridge in the world outside of the United States when it was completed.
Official Heritage Listing Information and Findings
Listed At: Category A
Historic Environment Scotland Number: LB47778
Description Consulting Engineers, Mott, Hay and Anderson in
association with Freeman Fox & Partners; commissioned 1947; constructed
1958-64. Suspension road bridge over Forth Estuary. Twin suspension
towers; main span 1006m with equal side spans of 408m (total 1822m);
approach viaducts at either end supported on paired piers (10 pairs to
S, 6 pairs to N), each joined at head by round arch; main deck and
suspension towers of steel; approach viaducts steel box girder with
concrete deck and concrete piers; suspension towers comprise twin legs
(each 150m tall) connected by lattice bracing supporting cable saddles.
Main cables anchored in rock below approach viaducts in concrete anchor
chambers with Corennie granite transferred aggregate facing. Vertical
suspender cables support main deck of bridge. Deck, containing two
carriageways and flanking pedestrian cycle/pathways cantilevered out on
either side (E and W); suspended deck supported by steel stiffening
lattice truss. Granite transferred aggregate facing to bases of approach
Statement of Special Interest A landmark building in
post-war Scotland, particularly given its location next to the famous
rail bridge of 1882-90 (and as a continuation of the tradition of
innovative Scottish engineering feats exemplified by the latter). In
international terms it was the first spun-cable suspension bridge to
challenge American designs of the period. It has an elegance deriving
from the lightweight appearance of its slender construction components
(American Designs of around this date eg Mackinac Bridge of 1957 and
Verrazano Narrows Bridge of 1963 were far more solid and heavier in
appearance). When it was completed in 1964 it was the longest suspension
bridge outside the USA and the fourth longest in the world (it has a
total span of 2828m). The engineers Freeman, Fox and Partners were also
responsible for 3 comparable large scale suspension bridges in the UK:
the Severn Bridge (1961-66), the Erskine Bridge (1967-71) and the Humber
Bridge (completed 1981). Of these the Humber Bridge has the longest main
span: 1410 metres, making it the longest in the world when it was built.
The Forth Road Bridge and the Severn Bridge have main spans of 1006 and
988 metres respectively. The Forth Road Bridge however stands out as the
earliest of all of them. Although the project was commissioned (and the
Forth Road Bridge Joint Board set up) in 1947, Treasury Authority was
not given until 1958 and it was in that year that construction began.
The contractors were the ACD Bridge Company, a consortium comprising 3
separate firms which was set up specially to undertake construction of
the Forth Road Bridge. The firms were: Sir William Arrol and Company
Ltd, The Cleveland Bridge and Engineering Company and Dorman Long Ltd.
Situated just to the S of the S approach is the administration building,
by Giles Gilbert Scott, Son and Partners.
Bibliography Plans may be viewed at National Archives, West Register
House; 'The Forth Road Bridge' in THE BUILDER, 4 September 1964; Forth
Road Bridge Joint Board, FORTH ROAD BRIDGE (undated, circa 1964); C
McWilliam, LOTHIAN in the 'Buildings of Scotland' series (1978; this
edition 1980) pp437-38; Moubray House Press and the Forth Road Bridge
Joint Board, SILVER HIGHWAY -THE STORY OF THE FORTH ROAD BRIDGE (1989);
notes courtesy of DOCOMOMO (1999).