Kylesku Bridge
The Kylesku Bridge (officially known since 2019 by its Gaelic name Drochaid a' Chaolais Chumhaing[1]) is a distinctively curved concrete box girder bridge in north-west Scotland that crosses the Loch a' Chàirn Bhàin in Sutherland. It is listed as category A, the highest grade.
Kylesku Bridge Drochaid a' Chaolais Chumhaing | |
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| Coordinates | 58°15′01″N 5°00′40″W grid reference NC233330 |
| Carries | A894, one footway |
| Crosses | Loch a' Chàirn Bhàin (Caolas Cumhann) |
| Locale | Kylestrome |
| Characteristics | |
| Design | Prestressed box girder |
| Material | Concrete |
| Total length | 276 m (906 ft) |
| Longest span | 79 m (259 ft) |
| No. of spans | 5 |
| Clearance below | 24 m (79 ft) |
| History | |
| Engineering design by | Ove Arup |
| Construction start | August 1982 |
| Construction cost | £4 million |
| Opened | July 1984 |
| Inaugurated | 8 August 1984 |
| Replaces | Kylesku and Kylestrome ferry |
| Location | |
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History
In June 1978 the Highland Regional Council asked Ove Arup & Partners Scotland to prepare a feasibility study for a bridge, in their capacity as consulting civil engineers, and was prepared by March 1979.[2]
Construction for the approach roads, costing £4 million, began in summer 1981. Construction of the bridge began in August 1982, with Morrison Construction and Lehane, Mackenzie and Shand the chief contractors.[2]
It was constructed by building out the supporting legs and then lifting into place the central span, which had been constructed on land and then moved onto a barge by rail and weighed 640 tonnes (630 long tons; 710 short tons).[3][4]
The cost of the bridge was £4 million, although was earlier budgeted at £2.75 million. The bridge opened to traffic in July 1984, and was formally opened by the Queen on 8 August 1984.[2]
In 2019, the bridge was classified by Historic Environment Scotland as a Category A structure, recognising it as "visually striking and technically innovative". It was also officially renamed to the Gaelic translation of its name, Drochaid a' Chaolais Chumhaing.[1]
Geography
The bridge crosses water which is approximately 120 metres (390 ft) wide and up to 25 metres (82 ft) deep, leading to fast tidal currents.[2] It replaced the ferry between Kylesku and Kylestrome, which was 400 metres to the east.
Design
The bridge is 275 metres (902 feet) long with a 79 metre long main span. The bridge deck is at a height of 24 metres (79 ft) above high water to provide navigation for ships.[2]
The bridge deck is supported by V-shaped inclined piers, with eight inclined legs, in order to reduce the length of the main span.[2] The lateral forces from each leg balance, so the total force on the foundations is vertically downwards.[2] The spread of legs supports the bridge in winds which can exceed 100 miles per hour (160 km/h), and also loads resulting from the curvature of the bridge.[4][2] There is no joint between the legs and the deck of the bridge, with the expansion joints and bearings being located at the abutments to facilitate straightforward maintenance.[4] The legs are formed from reinforced concrete and the deck from prestressed concrete using cables tensioned at up to 52200 kN.[2]
The bridge is designed to be sympathetic to the surrounding country, and the approaches were chosen to minimise changes to the landscape.[2]
References
- "Kylesku Bridge given A-list status and legal Gaelic renaming". www.thenational.scot. Retrieved 16 February 2019.
- Stears, H.S. (January 1985). "The Kylesku Bridge - Design and Construction". The Journal of the Institution of Highways and Transportation & HTTA. 32 (1): 16–20.
- "D-block GB-220000-933000 Bridge Building at Kylesku". bbc.co.uk. Retrieved 3 February 2015.
- Martin, J. M. (1986). "The Construction of Kylesku Bridge". ICE Proceedings. 80 (2): 317. doi:10.1680/iicep.1986.737.
