| Bridge Name: | Kylesku Bridge |
| Native Name: | Drochaid a' Chaolais Chumhaing |
| Native Name Lang: | Scottish Gaelic |
| Carries: | A894, one footway |
| Crosses: | Loch a' Chàirn Bhàin (Caolas Cumhann) |
| Locale: | Kylestrome |
| Engineering: | Ove Arup |
| Design: | Prestressed box girder |
| Material: | Concrete |
| Spans: | 5 |
| Begin: | August 1982 |
| Cost: | £4 million |
| Open: | July 1984 |
| Inaugurated: | 8 August 1984 |
| Replaces: | Kylesku and Kylestrome ferry |
| Coordinates: | 58.2573°N -5.0238°W |
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.
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 it 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 weighed .[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]
The bridge crosses water which is approximately wide and up to deep, leading to fast tidal currents.[2] It replaced the ferry between Kylesku and Kylestrome, which was approximately to the east.
The bridge is long with a 79m (259feet) long main span. The bridge deck is at a height of 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, 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 52,200 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]