BRITANNIA RR BRIDGE Anglesly, Wales 1850 Robert Stephenson HEW 110 SH542 710 {N53 12’ 58.5” W4 10’ 24.2” These coordinates are ¼ mile east of the bridge end and down river}
Robert Stephenson was the first to conceive of the tubular bridge: in essence a giant box girder. He used this concept (later adopted by his great friend and rival I.K. Brunel) to build his two famous tubular rail road bridges at Conway (1848) and here at Anglesly (1850). The tubes were built of wrought iron plates in a method that the iron foundries had developed for ship building.
The Britannia Bridge, which had paired central spans of 460’ with paired spans of a further 230 feet on either end, marked a huge advance in the use of this material since the longest wrought iron span to date had been of only 31 feet. They were to be joined end-to-end within the huge masonry tower piers.
“The four tubes for the two mainstream spans, each weighing 1800 tons, were built on the Caernarfon shore, then floated out and jacked up 100 feet onto the towers, a procedure like that at Conway and subsequently adopted for his Chepstow and Saltash bridges by I.K. Brunel. In June 1849, Brunel stood beside his great friend and rival Robert Stephenson to watch the launching of the first Menai tube.” (T. Seyrig “The different modes of erecting iron bridges” Min. Proc. Instn. Civ. Engrs. 1880-81 Pt 1 p. 63, 161-162 as quoted by W.J. Sivewright editor of “Civil Engineering Heritage: Wales and Western England” Thos Telford, London 1986) The hydraulic jacks that could lift such a weight were designed and built by the Cornwall firm of Tangye.
The massive bridge with its bold towers rising 100 feet above the bridge are to scale with the magnificent site. In 1970 an accidental fire in the timber roofing of the tubes caused them to warp. In the reconstruction that followed, a road bed was added on top of the rail road tracks and to support that extra weight, steel truss arches were added underneath the bridge. The resulting modern bridge still uses the masonry towers, but the airy effect is completely different than that of Stevenson’s original bold design.