Civil Engineering heritage: Scotland - Highlands and Islands
Date 2007
Event ID 929394
Category Descriptive Accounts
Type Publication Account
Permalink http://canmore.org.uk/event/929394
Union Bridge, Aberdeen
This bridge was built as part of Aberdeen’s Georgian civic improvements planned by road surveyor Charles Abercrombie and others to carry the new Union Street over the Den Burn some 46 ft below. Competitive designs were obtained in ca.1800 and that of David Hamilton for a triple-span structure with a main span of 50 ft was accepted. But, after construction had commenced, with Thomas Fletcher, Rennie’s assistant on the Aberdeenshire Canal superintending the work for the city, discrepancies
in the estimate and levels were discovered and the contract was cancelled.
This situation resulted in designs for single and triplespan bridges being prepared by Rennie. Telford submitted a sketch for a 150 ft span arch, and Fletcher a plan for a 130 ft single-span arch bridge in dressed granite masonry which, with minor modification, was approved by Telford and
built from 1801–05.
The rise of the arch is 29 ft and the depth of the arch-ring is 4 ft at the haunches reducing to 3 ft at the crown. To reduce weight the bridge was built with two 12 ft transverse tunnels within each spandrel. In addition there are two semicircular blind arches of 30 ft span above the east
abutment and a single arch over the west. The bridge was 40 ft between parapets. The contractor was William Ross and the contract sum £9816.
During 1906–08 the bridge was widened by the addition on each side of a three-pinned steel arch-rib which was tied to the main structure. This work was designed by William Dyack, Burgh Surveyor, and the steelwork contractor was Messrs. Findlay & Co., Motherwell.
R Paxton and J Shipway, 2007.
Reproduced from 'Civil Engineering heritage: Scotland - Highlands and Islands' with kind permission from Thomas Telford Publishers.
