timeline item
Results
Here is the information we have
on the item you selected
More like this
NEW SEARCH
| |
sign up for our newsletter
© 2017 Engineering Timelines
engineering-timelines@severalworld.co.uk
engineering timelines
explore ... how   explore ... why   explore ... where   explore ... who  
home  •  NEWS  •  search  •  FAQs  •  references  •  about  •  sponsors + links
Tongland Bridge
River Dee, Tongland, Dumfries & Galloway, Scotland, UK
Tongland Bridge
associated engineer
Thomas Telford
date  March 1805 - November 1806, opened 21st May 1808
era  Georgian  |  category  Bridge  |  reference  NX691533
ICE reference number  HEW 206
photo  © Malcolm Morris and licensed for reuse under this Creative Commons Licence
This is Thomas Telford’s first major bridge in Scotland. It has the longest span of any of his masonry arches north of the border and is an early use of the hollow spandrel technique that became one of his hallmarks. It is still in use, carrying the A711 over the River Dee to its junction with the A762.
In the first quarter of the 19th century, Scottish-born engineer Thomas Telford (1757-1834) worked on the survey and construction of some 1,480km of road and 120 bridges in Scotland. Known as the 'parliamentary roads' scheme, this work provided safe river crossings and access to remote areas of the country.
The project's earliest major bridge carries a road over the River Dee at Tongland (previously called Tongueland), linking Kirkcudbright with Ayrshire, Dumfries and Portpatrick. It is constructed in Gothic style, mainly of sandstone from Annan with Netherlaw stone for the copings.
The bridge sits between rounded splayed abutments. It consists of a main segmental arch, 34.1m in span and 9.75m in rise, flanked by three narrow pointed flood-relief arches of 1.8m span on each side. The soffit of the central arch is about 18.3m above the water. Between the main span and the side arches are semicircular cutwaters, which rise as turrets to parapet height and form pedestrian refuges at road level. The arches include rusticated voussoirs and the castellated parapet is supported on corbelling.
The bridge’s spandrels are hollow to mitigate outward pressure from internal fill, reduce weight on the foundations and enable inspection of the interior. Though Telford did not invent the concept, he developed the technique and promoted its use for large span masonry bridges.
At Tongland, the space between the spandrels is divided by longitudinal walls into four equal cavities, each wide enough to accommodate a person. Transverse walls are located above the piers. The voids are roofed with slabs that form the base of the bridge deck.
Telford planned and designed the structure, though its form owes much to artist and architect Alexander Nasmyth (1758-1840). Despite Telford’s admiration of Gothic styling, he did not adopt Nasmyth’s proposed castellation over the side spans or his eight octagonal towers above stringer level.
On 29th July 1803, a contract was let to local stonemasons Samuel McKean, Alexander McKean, Samuel Hyslop and Andrew McGuffery (or McGuffie) for the sum of £2,420. The foundation stone was laid on 22nd March 1804. However, erecting secure timber centring to support a 40.5m arc of stone 1.1m deep proved beyond their abilities. The works were swept away by flood water in August 1804, by which time £3,005 had been spent.
On 19th October 1804, Telford inspected the site. The masons were relieved of their obligation to build the bridge and Adam Blane was brought in as resident engineer. Construction recommenced in March 1805.
The arch ring was finished on 29th August 1805, by day labour working under Blane's direction. The bridge was passable from November 1806, and fully complete by 21st May 1808. The total cost was £7,710 — £1,150 from public subscription and the majority financed by the Stewartry's Commissioners of Supply.
Tongland Bridge was strengthened in the mid-20th century by the construction of a reinforced concrete slab across the tops of the longitudinal spandrel walls.
It was Category A listed in November 1971, and de-scheduled in March 1996. In 2005, a bicentenary commemorative plaque was unveiled by the Institution of Civil Engineers.
Architect: Alexander Nasmyth
Resident engineer: Adam Blane
Research: ECPK
bibliography
http://portal.historicenvironment.scot
https://canmore.org.uk
www.ice.org
reference sources   CEH SLBBDCE1
Location

Tongland Bridge