Dornoch Firth Bridge
| Dornoch Firth Bridge | |
| Ross-shire, Sutherland | |
|---|---|
_-_geograph.org.uk_-_286814.jpg) Dornoch Firth Bridge | |
| Location | |
| Carrying: | A9 road |
| Crossing: | Dornoch Firth |
| Location | |
| Grid reference: | NH747852 |
| Location: | 57°50’38"N, 4°6’36"W |
| Structure | |
| Length: | 2,929 feet |
| Design: | Prestressed box girder on inclined leg portals |
| Material: | Concrete |
| History | |
| Built 1989 -1991 | |
| Information | |
The Dornoch Firth Bridge is a road bridge over the Dornoch Firth, carrying traffic between Tain and Dornoch.
History
The bridge was built in 1989-1991 to complement the substantial improvements of the A9 being made between Inverness and Tain, including the cable-stayed Kessock Bridge at Inverness in 1982. The Dornoch Bridge was to be the final link in the chain.
Ove Arup and Crouch Hogg Waterman of Glasgow as a joint-venture won the tender with a quote for £9.5 million. There were proposals that the bridge should be constructed so as to allow the Far North railway line to also benefit from the shorter route, with the potential for up to 45 minutes to be saved on the journey between Inverness and Thurso/Wick. However this part of the scheme failed to secure government funding, and so only a road bridge was built.[1]
Eventually the bridge cost £13.5 million. At the time it was one of the longest bridges in Europe built with the cast-and-push method, or incremental launch.
The bridge was opened by The Queen Mother on 27 August 1991. The bridge replaced, by way of a roundabout with the A836 to the south and a road junction with the A949 to the north, the 26-mile round trip over Bonar Bridge.
Design
Each of the 21 spans is about 144 feet long. Prestressed concrete rather than steel was chosen as the material to improve the life of the bridge. The design had to be approved by the Royal Fine Art Commission for Scotland.
The bridge deck was built in a temporary factory 20 yards south of the southern end of the bridge. Each section of the bridge was pushed with 600 tons of hydraulic force over PTFE bearings on the top of the bridge supports. The launch nose section[2][3] had a light steel composition to reduce the cantilever moment as it was inched over an open span. Each deck section was constructed as around 21 metres in length – half a span. The concrete used welded mat reinforcement. The pre-stressing of each section had 38 Macalloy bar tendons of 40 mm thickness. The sections would be cast on a Monday morning and pushed on a Friday, this later being on a Thursday. Each deck section weighed around 14,000 tons.
See also
- Cromarty Bridge, further to the south.
Outside links
References
- ↑ "A Better Railway for the North". Caithness.org. http://www.caithness.org/railway/corusreport/background.htm. Retrieved 2018-03-01.
- ↑ Launch nose side view
- ↑ Launch nose front view