Publication Account
Date 1986
Event ID 1017680
Category Descriptive Accounts
Type Publication Account
Permalink http://canmore.org.uk/event/1017680
Thomas Telford's bridge at Craigellachie, erected in 1814-15 across the River Spey, and its sister bridge built two years earlier across the Dornoch Firth at Bonar, Sutherland, together represent his two major works in Scotland that employed the structural use of cast iron. They were basically identical in design and shared the distinction of being prototypes for his several large arch-bridges subsequently built in Britain. The ironwork for both bridges was cast by William Hazeldine in his foundry at Plas Kynaston in North Wales and was probably erected on site by his foreman William Stuttle. Prior to its reconstruction above the arch-ribs in 1963, the Craigellachie bridge bore the inscription 1814/ CAST AT PLAS KYNASTON/ RUABON DENBIGHSHIRE, cast in bold relief at one end of the parapet skirting.
Built in the form of a segmental arch with a rise of 20 ft 9 in (6.33m), and a width of 15 ft m1 in (4.60m), it spans 151 ft 6in (46.18m) between granite abutments topped with twin turrets and raked at an angle radial with the arch. Its four longitudinal ribs are made up of seven castings, each pierced with latticed subdivisions and bolted together through transverse ribs, also pierced with openings to lessen the weight. For lateral stability the ribs were further stiffened by latticed cross-plates extending over the full width of the arch extrados, and by a series of stout horizontal tie-bars fixed at intervals between .the ribs along their lower edge. Rows of diagonal struts, set within the arch spandrels, provided longitudinal bracing and direct support to the road-bearers, also stiffened transversely by tie-bars fixed to their intersections, and by two pairs of diagonal swaybraces on each side of the crown. In general, the various members were connected by bolted flanges, or by a system of joggle-and-socket Joints cast on the frames and evidently held together simply by iron pins or wedges and the compressive forces acting upon them.
Information from ‘Monuments of Industry: An Illustrated Historical Record’, (1986).
