Royal Albert Bridge
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- For other bridges bearing the name Albert, see Albert Bridge.
- Brunel truss, Brunel truss bridge, and lenticular truss redirect here.
Image:Royal albert bridge hist.jpg Image:Saltashrab.jpg Image:Royal Albert Bridge.JPG
The Royal Albert Bridge (sometimes called the Brunel Bridge or Saltash Bridge) spans the River Tamar in the U.K. between Plymouth, on the Devon bank, and Saltash on the Cornish bank. It carries the Great Western Main Line in and out of Cornwall.
The bridge was designed in 1855 by Isambard Kingdom Brunel for the Cornwall Railway Company after Parliament rejected his original plan for a train ferry across the Hamoaze. The bridge consists of two main spans of 455 feet (139 m), 100 feet (30 m) above mean high spring tide, plus seventeen much shorter approach spans. Opened by Prince Albert on May 2, 1859, it was completed in the year of the great engineer's death.
The structure was the third in a series of three notable wrought iron bridges built in the period, and was influenced by the preceding two, both by Robert Stephenson. The two central sections of the bridge are novel adaptations of the design employed for the High Level Bridge across the River Tyne in Newcastle Upon Tyne, being spans composed of a tubular arch in compression; a suspension chain in tension and acting to hold in the bridge abutments. Between these two chords are supporting cross bracing members and suspension members which trail beneath the suspension chain to carry the railway deck. The method of construction was similar to the Britannia Bridge across the Menai Strait in north Wales, in that the spans were constructed on land, then floated into position and raised. Unlike the Britannia, however, the central piers were built up in height three feet (1 m) at a time, and the spans raised that distance, until the design height was achieved. (For the Britannia, the piers were built to full height, and then the span hoisted to design height.) The difficulty of its construction rates it as one of Brunel's great railway achievements.
A short distance to the north of Brunel's bridge, the Tamar is crossed by the Tamar Bridge carrying the A38, one of the two trunk roads connecting Cornwall to Devon.
[edit] As a truss type
The truss is notable for its arched upper and lower chords, with the lower chord withstanding only tension. This truss is used in some modern constructions, for example the Arizona Cardinals's new (multiple–use) stadium. Two such trusses are employed and the upper chords corresponds to the arch of the roof and these carry tracks to allow fabric covered frames spanning the trusses to roll down on each side to expose the sky in appropriate weather. (Another innovation in this stadium is that the natural grass field rolls out as a unit on rails to an outside area for sun exposure and to clear the playfield for a hard-surface replacement.)[1]
[edit] External links
[edit] References
- Binding, John (1997). Brunel's Royal Albert Bridge: A Study of the Design and Construction of his 'Gateway to Cornwall' at Saltash. Truro: Twelveheads Press. ISBN 0-906294-39-8.
- Charles Matthew Norrie (1956). Bridging the Years - a short history of British Civil Engineering. Edward Arnold (Publishers) Ltd.
