Tubular bridge

Conwy and Britannia Bridges

Main article: Conwy railway bridge, Britannia Bridge

The Conwy railway bridge carries the North Wales coast railway line across the River Conwy between Llandudno Junction and the town of Conwy. The wrought-iron tubular bridge was built by Robert Stephenson to a design by William Fairbairn and is similar in construction to Stephenson's other famous tubular bridge, the Britannia Bridge across the Menai Strait. It was completed in 1848 and officially opened in 1849. 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 was performed by Fairbairn. The successful result enabled the much-larger Britannia Bridge to be built. The current Conwy bridge has been reinforced by extra columns under the bridge into the river but is otherwise virtually unchanged since it was built.

Before the Britannia Bridge was constructed, Fairbairn conducted "the most celebrated of all engineering experiments on the grand scale",{{Cite book

Other bridges

The unconventional nature of the tubular girder bridge was not widely accepted. John Fowler's 1847 tubular girder design for Torksey used tubes that were only 10 ft high and placed the railway deck between them, rather than inside.{{Cite web

Legacy

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.

In the case of the Britannia Bridge, this technology allowed a bridge with spans up to 460 ft long to be constructed, when until then the longest wrought iron span had been 31.5 ft.

References

• {{Cite book
• John Rapley, The Britannia and Other Tubular Bridges: And the Men Who Built Them, Tempus (2003).