Chepstow Railway Bridge

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.

The Admiralty had insisted on a 300-foot (91 m) clear span over the river, with the bridge a minimum of 50 feet (15 m) above high tide.

Robert Stephenson had bridged the River Conwy (1848) and the Menai Straits (1850) with spans of 400 and 450 feet (140 m) respectively, using large box-girder sections of riveted wrought iron.

This was the same year as Stephenson's tied arch High Level Bridge at Newcastle upon Tyne, which was supposed to have influenced Brunel at Chepstow.

However, Brunel's solution for the latter was to make a leap forward, based, nevertheless, on sound engineering principles and a variation of the tied-arch theme.

The tubular wrought-iron girder – be the cross-section rectangular, triangular or circular – formed a most efficient truss component.

[5] He was also present to provide Stephenson moral support when the great Britannia box-girders were floated across the river prior to being jacked up to their final positions.

With regard to the appearance of the bridge, the Illustrated London News stated that "the peculiarity of the site did not permit any display of 'Art' – that is, of architectural embellishment; indeed, a pure taste rejects any attempt to decorate a large mechanical work with sham columns, pilasters, and small ornamental details.

After it was completed, Finch remained in Chepstow, and developed a major engineering and, later, shipbuilding business on the site, beside the river.

[8] However, even Brunel was not infallible, and his foresight in allowing for slight movement of the suspension chains against supports on the bridge-deck to relieve stress, led to a weakening of the structure.