A tubular bridge is a bridge built as a rigid box-girder section within which the traffic is carried. Famous examples include the original Britannia Bridge over the Menai Strait, the Conwy railway bridge over the River Conwy, designed and tested by William Fairbairn and built by Robert Stephenson between 1846 and 1850, and the original Victoria Bridge in Montreal.
Conwy and Britannia Bridges
thumb|Conwy Bridge.Construction of second tube, September, 1848
The Conwy railway bridge carries the North Wales coast railway line across the River Conwy between Llandudno Junction and the town of Conwy. a series of experiments "of a gigantic character". This is now considered as the first box-girder bridge, rather than a pure tubular bridge. Despite this, it was initially rejected after completion by the Board of Trade’s inspector, Captain Lintorn Simmons, and the design was also criticized by the Institution of Civil Engineers. When the bridge was strengthened in 1897, this was done by added a central truss above the deck rather than by strengthening the box.
- John Rapley, The Britannia and Other Tubular Bridges: And the Men Who Built Them, Tempus (2003).