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Glasgow Bridge
River Clyde, Glasgow, Scotland, UK
Glasgow Bridge
associated engineer
Thomas Telford
Blyth & Westland
date  1833 - 1st January 1836, 1894 - 1899
era  Georgian  |  category  Bridge  |  reference  NS586647
ICE reference number  HEW 2490
photo  © and licensed for reuse under this
The present Glasgow Bridge, also known as Jamaica Street Bridge, incorporates the elegant stone façades of Thomas Telford's 1836 construction but is wider and more-solidly founded. Blyth & Westland's rebuilding dates from 1899. Glasgow Bridge carries the A77 over the River Clyde in central Glasgow and lies just east of the Caledonian Railway viaduct.
There have been three bridges on this site since the medieval period. The first was a seven-arch masonry bridge by brothers William (1734-90) and Robert (1733-1811) Mylne, built between 1768-72. The second was Telford's masonry bridge, also of seven arches. It was completed in 1835 and opened to traffic on 1st January 1836.
Sir Alexander Gibb (1872-1958) — whose great grandfather John Gibb (1776-1850) was the contractor for Telford’s bridge — called it "perhaps the most beautiful of all [Telford's] bridges … a fitting crown to his creative life". This bridge was 18.3m wide, and despite developments since 1835, as it's form has been retained, it's still possible to appreciate something of its impact.
The progressive effects of navigational dredging had weakened the foundations of each of these bridges in turn. And as the city’s population and industrial capacity increased, so did the need for a wider, stronger bridge. A higher bridge would also have helped shipping to pass without lowering masts or funnels.
In 1892, engineer Blyth & Westland proposed a granite arch bridge with four high spans, 30.5m wide between parapets and estimated to cost £240,000. Glasgow Corporation declined this proposal because, apart from costing more than rebuilding the original, Telford’s bridge was held in high regard by Glasgow's citizens.
So, the third bridge on the site is a re-build of Telford's bridge by Blyth & Westland. Work began in 1894 and Telford’s bridge profile, with its gently curving extrados rising less than 900mm from the banks to the bridge centre, and arches with spans from 15.9m to 17.9m wide, was retained. Much of the original Aberdeen granite was reused.
The bridge is now 24.4m wide and has much deeper foundations than its predecessor. Instead of timber piles, the piers are founded on 4.6m diameter steel cylinders sunk into the river bed using pneumatic pressure, then filled with concrete. The piers are founded at a minimum depth of 23m below the arch springings, though some of them are more than 30.5m below this level.
Manual excavation for the piers was carried out inside a 2.75m high chamber filled with compressed air. However, at the greatest depth, an air pressure of 296.5kN per sq m (almost three times atmospheric pressure) was required in order to repel the water — virtually impossible working conditions for the labourers.
Work was completed in 1899, at a cost of £129,500. The gas lights that had adorned the parapets of Telford’s bridge were replaced by electric lamps along the central reservation.
A temporary 18.3m wide, eight-span bridge consisting of steel beams supported on timber piles had been erected to accommodate traffic during construction. This bridge was built to the east of the new bridge and opened in March 1894. It was the first bridge in Glasgow to have electric lighting.
Contractor (1835): John Gibb
Contractor (1899): Morrison & Mason, Glasgow
Steelwork (1899): Sir William Arrol & Co Ltd
Research: ECPK
bibliography
http://canmore.rcahms.gov.uk
www.theglasgowstory.com
reference sources   CEH SLB
Location

Glasgow Bridge