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Buildwas Bridge, site of
River Severn, Buildwas, Shropshire, UK
Buildwas Bridge, site of
associated engineer
Thomas Telford
date  17th April 1795 - 24th June 1796
era  Georgian  |  category  Bridge  |  reference  SJ644044
photo  PHEW
Thomas Telford’s cast iron Buildwas Bridge over the River Severn was the second of four bridges on this spot. It was Britain’s second major iron bridge, after the pioneering Iron Bridge (1781) at Coalbrookdale only 3km downstream. Buildwas’ single arch remained in place for 110 years.
The first bridge on the site was a medieval stone bridge with a large central arch flanked by two smaller arches. It was constructed by the monks of nearby Buildwas Abbey (founded 1135, disbanded 1536) in around 1318.
The Severn is a turbulent river, and the stone bridge had undergone a series of repairs, the last in the early 1790s — under the supervision of Shropshire’s County Surveyor Thomas Telford (1757-1834). However, the bridge was swept away in floods during January and February 1795.
By April that year, Telford had designed a replacement. He decided to use a single span, avoiding the use of piers, which can obstruct water flow. His design was also intended to resist the tendency of the sides of the river gorge to move inwards. This movement can damage a bridge, as it had at Iron Bridge, where the abutments were affected. Telford's cast iron superstructure was 5.5m wide and spanned 39.6m, with the main arch flanked by curved ribs of greater rise and fall.
Writing about his bridge, Telford said: "I made the arch 130 feet span. The roadway rested on a very flat arch calculated to resist the abutments if disposed to slide inwards as at Coalbrookdale, while the flat arch was itself sustained and strengthened by an outer arched rib on each side of the bridge springing lower than the former and also rising higher thus introducing more of the principle of timber trussing than of masonry. The back of each abutment is in a wedge shape so as to throw off laterally much of the pressure of the earth".
In a demonstration of evolving design efficiency, Telford's bridge had a span 9.1m wider than Iron Bridge, though it contained only 181 tonnes of iron — Iron Bridge has more than twice as much at 385 tonnes.
The Buildwas contract was signed on 17th April 1795, for a sum of £3,700. The contract period was stipulated as nine months, with a forfeit of £5 for every additional month plus a guarantee for five years after construction. In the event, the bridge was completed in a little over 14 months, on 24th June 1796, and the final cost was about £6,500.
Despite Telford's design, movement of the river banks continued. In 1818, he reported that repairs to the wing walls and abutments were required. In 1876, some damage to the ironwork was discovered. In 1885, part of one of the stone abutments failed because of ground movement.
In 1889, the main arch broke on the east side and was repaired by the Horsehay Company in 1890. In 1901, another fracture occurred and Sir Benjamin Baker (1840-1907) was consulted. A new structure was recommended, as the ongoing steady movement of the banks was constantly compressing the brittle cast iron arch.
In 1905, the arch was replaced by a Pratt hog-back steel lattice girder bridge with a nominal 40m span and a 6.6m wide deck. It was supported on Telford's abutments, anchored at the south but free to move at the northern end to prevent distortion. Though the abutments had remained vertical and parallel since 1796, they had encroached 900mm into the gorge by 1905 and a further 900mm by 1967.
The third bridge was demolished in 1992 and its wider replacement, the present structure, was completed the following year. It is a steel girder bridge carried on concrete abutments and piers.
A remnant of Telford's Buildwas Bridge survives: a section of cast iron arch marked "ANNO 1796" has been built into a memorial wall north of the bridge, detailing the history of the bridges on the site.
Ironwork: Coalbrookdale Company
Contractor (1890-1905 repairs): Horsehay Company
Contractor (1905 abutments): Scale & Smallman
Research: ECPK
bibliography
http://infoscience.epfl.ch
www.broseley.org.uk
www.ice.org.uk
www.ironbridge.org.uk
reference sources   BDCE1Smiles2
Location

Buildwas Bridge, site of