Chepstow railway bridge was built to the instructions of
Isambard Kingdom Brunel in 1852. The "Great Tubular Bridge" over the
River Wye at
Chepstow, which at that point forms the boundary between
Wales and
England, is considered one of Brunel's major achievements, despite its appearance. It was economical in its use of materials, and would prove to be the design prototype for Brunel's
Royal Albert Bridge at
Saltash.
Background
Brunel had to take the two tracks of the
South Wales Railway across the river Wye. The
Admiralty had insisted on a clear span over the river, with the bridge a minimum of above high tide. The span would have to be self supporting, since although the
Gloucestershire side of the river consists of a
limestone cliff, the
Monmouthshire side is low-lying
sedimentary deposit subject to regular flooding. Thus on that side, there was nowhere for an
abutment capable of either resisting the outward push of an
arch bridge, or the inward pull of a conventional
suspension bridge. In any case, neither could be used: an arch bridge would not have met the height and width restrictions imposed by the Admiralty, and suspension bridges were notoriously unfit for carrying railway trains. The concentrated weight caused the chains to deflect, allowing the bridge-deck to ride dangerously up and down. A self-supporting
truss bridge was the only option.
Robert Stephenson had bridged the
River Conwy (1848) and the
Menai Straits (1850) with spans of 400 and ...
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