Miscellaneous

Avon Bridge Power Station: misc_abps170

Another photograph showing the extent of the 1947 floods at the Avon Bridge Power Station. The Great Western Railway’s main line crossed the River Avon on a wrought iron plate girder viaduct built in 1875 to replace the original timber viaduct. The longitudinal plate girders rested on a series of transverse girders, each supported by a pier consisting of four wrought iron columns (see misc_abps171 for a close up of the tops of the piers).

Prior to the 1847 ‘Inquiry into the Application of Iron to Railway Structures’, all railways except the Great Western Railway had adopted the cast iron beam bridge. Brunel had stood alone against this practice and had insisted on either timber or wrought iron in any structure which might be subjected to tension. He regarded cast iron as an uncertain material, difficult to make perfectly homogeneous and therefore intrinsically unsafe. The enquiry had followed the death of five people on a train when the compound cast iron beam bridge over the River Dee failed on 24th May 1847. Some railways continued to use cast iron bridges until they were prohibited for new construction in 1882. That year four passengers were killed when the cast iron girder bridge at Inverythan failed. Only after another failure at Norwood Junction on 1st May 1891, were railway companies forced to put in place a programme of replacement for all the cast iron girders on existing railway lines.

At Warwick, the original Avon Bridge viaduct built in 1852, was designed by Brunel and consisted of a timber viaduct of thirty 25 feet long spans. This design featured queen post through trusses, which were suitable for spans up to 41 feet and were widely used by the Great Western Railway. The queen post through truss bridge structure was introduced in 1846 and the last known example at Waterhead on the Dartmouth & Torbay Branch was replaced in 1928 after a life of 64 years.

Robert Ferris

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