Gwynedd Archaeological
Trust Regional Historic Environment Record
Britannia Tubular Bridge, Menai Straits
Primary Reference Number (PRN) : 4012 Trust : Gwynedd Community : Pentir Unitary authority : Gwynedd NGR : SH5416071000 Site Type (preferred type first) : POST MEDIEVAL BRIDGE Status : Listed Building II, Listed Building II
Summary : Robert Stephenson designed the two great bridges of the Chester and Holyhead Railway: Conwy and Britannia. Conwy was the first to be built using the innovative iron tubes which carried the train lines, and acted as a trial for the massive bridge across the Menai Straits. The tubes were chosen as it was considered that they would be self-supporting.
The first Britannia Bridge was very different to the modern one. The original bridge, opened in 1849, was constructed from wrought iron rectangular tubes, as at Conwy, but it had three intermediate towers between the abutments, and four spans of two parallel tubes. The two longest sections of each tube spanned 138 metres. The tubes were suspended 30 metres above sea level in accordance with Admiralty demands. They were constructed on the Caernarfon shore and then floated out and lifted into position where they were joined together to form single, continuous girders without need for supporting arches or suspension chains (although the towers were built tall enough to accommodate them). The tubes were protected from the weather by a roof of timber and tarred hessian, and were occasionally coated in tar themselves, although it was this protection that resulted in the partial destruction of the tubular bridge in 1970. The roof caught fire and it rapidly spread across the bridge. The intense heat damaged the tubes beyond repair.
The rebuilt bridge followed an early design of Stephenson's that the Admiralty had originally rejected. The new main spans of the bridge are lattice steel arches supported by N-truss spandrel bracing in each half arch, and in 1979 an upper deck was added to carry a road across the Straits, although the original towers, abutments and monumental lions remain.
Description : The bridge was built by R. Stephenson in 1845 and opened in 1850 to carry the railway across the Menai Straits. Comprises two rectangular tubes of steel in four spans, with stone abutment towers and approaches with sculptured lions. Damaged by fire in 1970 and the sides were removed. <1> <2> <3> <4> <5>
1850, twin rectangular tubes of steel, 4 spans, stone abutment towers, sculptured lions at approach; erected by Stevenson. <7>
The Brittannia and Conway Bridge, Robert Stevenson's masterpiece opened in 1850, which carried the Chester & Holyhead Railway over the Menai Straits, was the most celebrated bridge of its age. Remarkable for its originality, the design (and that of its smaller counterpart at Conway) consisted of a hollow tube made of wrought-iron plates. It evolved from model tests and from mathematical calculations carried out by William Fairbairn and Eaton Hodgkinson. This synthesis of theory and practice was applied for the first time to these structures and marked the advent of structural engineering as we know it today. As such, the importance of these bridges cannot be over-estimated. <8>
Sources :
Derby, S. , 2017 , By investigating the conception, design, and ultimate failure of the Britannia Park venture, can we evaluate the potential significance of this site in mid-19th century Caernarfonshire?
Ordnance Survey , 1973 , SH57SW , <1>
, 1964 , Ogwen Rd. , <2>
Burton, A. , 1977 , Industrial Archaeological Sites of Britain , <3>
Hudson, K. , 1976 , Industrial Archaeology , <4>
Ordnance Survey , 1979 , SH57SW 34 , <5>
Various , PRN 4012 , <6>
Royal Commission on Ancient and Historic Monuments , 1999 , RC Buildings Records , <7>
Royal Commission on Ancient and Historic Monuments , PRN 4012 , <8>
Lynch, F. , 2009 , Anglesey Past Landscapes of the Coast , <9>
Beazley, E. , 1985 , Transactions of the Ancient Monument Society , <10>
Gwyn, D. & Williams, M. , 1996 , A Guide to the Industrial Archaeology of North West Wales , <11>