Crumlin Viaduct
NO LONGER EXTANT
This was the tallest viaduct in Great Britain until its demolition in 1965.
1852 the Board of the Newport, Abergavenny and Hereford Railway invited tenders for the construction of a wrought iron bridge as part of the Taff Vale Extension which would connect with the Taff Vale Railway.
Charles Liddell, the railway's chief engineer, preferred Thomas Kennard's submission. Kennard’s plan incorporated his own-patented modification of the Warren Truss. The iron castings for the Viaduct were made by the Falkirk Iron Co; most of the wrought iron work was made by the Blaenavon Iron and Coal Co, both Kennard companies.
An assembly plant was built at Crumlin called the Crumlin Viaduct Works where the various sections of ironwork were put together.
The Crumlin Viaduct was finished in 1855; it consisted of ten, 150 feet long Warren Truss Spans 200 feet above the valley floor.
1857 The Viaduct was formally opened.
1858 In an address to the Institute of Engineers in Scotland Professor W. J. Maquern referred to the truss form "invented by Captain Warren used on the Crumlin Viaduct constructed by Messrs Liddell and Gordon as engineers and Mr Kennard as contractor". The bridge was the first product of the Crumlin Viaduct Works.
By the mid-1860s it was apparent that the viaduct was suffering from vibration, and some deterioration was apparent, necessitating repairs and strengthening. Holes for pins in the Warren girders were elongated by wear; tie-bars between the cast iron legs were rusting; timber decking was decayed. Considerable strengthening was recommended by Captain Tyler and separately by John Fowler. The work was undertaken by Messrs Kennard, and completed in late 1866.[1]
The viaduct is categorized here as a Pin-jointed Truss Bridge. However, some sources state that pin-connected joints were replaced by riveted gusseted joints in 1865-6. In fact this 1955 photograph[2] shows that pin-joints were retained for the outer girders, while the more heavily-loaded inner girders were stiffened by riveting on triangular gussets.
This viaduct, with its tall piers assembled from cast iron tubes, influenced Gustave Eiffel in his design of his railway viaduct over the Garonne at Bordeaux, started in 1858[3]
1965 'Requiem for a viaduct.
A week ago last Wednesday there was a report in this newspaper that a contract had been let for the demolition of the Crumlin Viaduct, completed in 1857 to carry the Taff Vale extension of the Newport, Abergavenny and Hereford Railway across the Ebbw Vale, four miles west of Pontypool. Nineteenth-century engineering of this sort has contributed so much to the fabric of present-day architectural and engineering thinking, and this bridge in particular is so significant in structural history and so elegant in conception that we cannot let it go without a special valediction.
Its designer and builder was T. W. Kennard who, with his partner Warren, had some years before patented the Warren Girder, made of comparatively thin and light members, pin-jointed together into a latticework of triangles; this bridge was the first large structure to use this principle, and it is a principle which is still a commonplace of engineering today. There is another thing about the construction of the bridge which has a modern ring about it, and that is its use of prefabrication. The girders, of which there are four to each span, make use of large number of identical parts, and these were all made to fine limits of accuracy in the works before being sent to the site. Kennard introduced at Crumlin a fresh conception of dimensional accuracy into structural engineering which it had not known before. Because of these new methods of fabrication, a gang of 20 men put each girder together on the ground in two days, and took only one further day to hoist it to its final position at the top of the piers, 190 ft. above the floor of the valley. ....'[4]