3674

 

II  

Designated  

03/03/1966  

22/09/1997  

Britannia Tubular Bridge  

 

Gwynedd  

Pentir  

Bangor  

Treborth  

254247  

370888  

 

Spanning the Menai Strait to Llanfairpwllgwyngyll, and W of the Menai Suspension Bridge.  

Transport  

 

Originally built as a railway bridge for the Chester and Holyhead Railway, and designed by the renowned engineer-in-chief to the railway, Robert Stephenson, in association with Francis Thompson, the railway's architect, and Sir William Fairbairn as consultant engineer. The bridge made novel use of a continuous tubular construction of iron plates, forming twin tubes, set at the centre span 31m (102ft) above the high water line, each pair spanning 140m (459ft 3in) between the intermediate water piers, the stonework built by Nowell Hemingway and Peason, and the whole scheme costed £674,000. Each of the two pairs of tubes carrying the plateway, was 9.1m x 4.45m (30ft high x 14ft 8in) wide, fixed at the centre with rolling expansion joints in the Anglesey and Caernarvon Towers. It was opened at a fine ceremony in 1850. The C & H Railway was amalgamated with the London and North Western Railway in 1858. After a serious fire on 23.5.1970, the bridge was extensively modified and strengthened to provide a road carriageway above and in addition to the rail track, designed by Husband & Co for British Railways, using The Cleveland Bridge & Engineering Co Ltd as contractors.  

The bridge piers are of rock-faced Anglesey limestone (Penmaen marble), set on a plinth, and Runcorn sandstone and brickwork. Each of the 2 central water piers is 67.5m (221ft 3ins) high from foundation on the sea bedrock, and rise in rock-faced coursed stone with battered sides to an ashlar corniced top raised on large corner blocks forming voids, originally designed to take suspension chains over rockers, on each face, all in an Egyptian Pylon style. The piers are voided, and stone lintels 6m (20ft) long span the rectangular holes for the twin tubes, with bold plat bands at the level of the top and bottom of the tubes. Each side face carries a symbolic engineering motif based on linked driving rods. The outer spans spring to similar abutment towers, flanked by sculpured lions on high plinths (q.v.). A huge figure of Britannia designed by Thompson for the centre pier was never executed. Inscribed on the approach face 'Erected Anno Domini MDCCCL Robert Stevenson Engineer'. The modified bridge, opened in 11/6/1980, consists of braced rivetted steel section arches with 'N'-truss spandrels spanning between the earlier piers, with the roadway carried on stanchions above the railway. The side spans are in reinforced concrete.  

 

In its original form, the bridge was one of the most audacious and exciting monuments of the great age of engineering where Britain was at the forefront of such innovatory developments. Included at Grade II notwithstanding the fact that the original design has been vitiated after the fire; the surviving piers combine monumental architectural qualities with significant evidence for the original engineering.