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Robert Stephenson was responsible for building this bridge to take the Chester and Holyhead Railway Line across the fast-flowing, tidal River Conwy.
Stephenson proposed a wrought iron 'tubular' bridge, and contracted William Fairbairn to undertake experiments to determine the best form.
A similar form of construction was adopted for the Britannia Bridge across the Menai Strait.
Tenders for the ironwork were received from a number of major companies, including Fairbairn, Hick, Rothwell, and James Lillie, but none were acceptable. Surprisingly, a masonry contractor, William Evans (of Cambridge), bid to undertake the masonry and iron work, and his bid was accepted (to include construction of six pontoons for floating the tubes).
1847 At the request of William Evans, Richard Roberts produced the 'Jacquard Punching Machine,' an automatic tool for accurately punching the rivet-holes. This allowed for rapid production of the tubes as well as increasing their strength and reducing the cost of construction.
1850 Bridge completed.
1850 Edwin Clark published "The Britannia and Conway Tubular Bridges". Conwy railway bridge carries the North Wales coast railway line across the River Conwy between Llandudno Junction and the town of Conwy.
Being the first tubular bridge to be built, the design needed much testing on prototypes to confirm that it would be capable of carrying heavy locomotives, the testing being performed by Fairbairn. The successful result enabled the much larger Britannia bridge to be built.
In 1899 the span was reduced by 90 ft by introducing two pairs of cast iron columns in the bridge. Additional vertical strengthening ribs were attached to the girders above the columns. The work commenced in 1896, and was undertaken by the Cleveland Bridge and Engineering Co of Darlington. The maximum depth of the iron columns in the river bed was 70 ft.
Since the destruction by fire of Britannia Bridge in 1970, Conwy railway bridge remains the only surviving example of this means of construction undertaken by Stephenson.