Silly Bridge (MLN14779)

Summary

A tall triple arch accommodation overbridge, with semi-elliptical spans, set in a deep cutting. Erected c. 1837-40 and widened c. 1890-3.

Reasons for Designation

Silly Bridge is designated at Grade II for the following principal reasons:
* Date: it dates from the first pioneering phase of the GWR, and of railway construction nationally;
* Design, engineering & material interest: a fine example of a triple-arch bridge widened in the 1890s phase of quadrupling, and a notably tall structure with considerable architectural stature;
* Degree of survival: the 1840 elements are very well-preserved including both piers, two arches, the southern abutment and parapet all intact; the later elements are also well-preserved. The extension was designed with immense respect for the existing structure; the division between the two phases strikingly and instructively clear, so that the nature of the widening works can be readily understood;
* Historic interest: it was designed by Brunel himself.

History

The Great Western Railway was authorised by an Act of Parliament in 1835 to construct a line from London to Bristol. At 118 miles this was slightly longer than the other major trunk railway of its time, the London and Birmingham (112 miles) and considerably longer than other pioneering lines. Construction of the line began in 1836, using a variety of contractors and some direct labour. The first section to be completed, from London to Maidenhead Riverside (Taplow), opened in 1838, and thereafter openings followed in eight phases culminating in the completion of the whole route in 1841.

The engineering of the railway was entrusted in 1833 to Isambard Kingdom Brunel (1806-59), who was already known for his engineering projects in Bristol. More than any other railway engineer of his time he took sole responsibility for every aspect of the engineering design, from surveying the line to the detailing of buildings and structures. He sought to achieve as level a route as possible and, working from first principles, he persuaded the Directors of the GWR to adopt a broad gauge of 7ft 0¼ in rather then the standard (4ft 8½in) gauge in use on other lines. A two track broad gauge line was 30ft wide, and this determined the span of the overbridges and other structures. Except for larger bridges such as Maidenhead Bridge, the majority of Brunel’s masonry bridges did not need to be as innovative as his works in timber and iron, and his structures followed the typical architectural idioms of his time, but they were all beautifully detailed and built and together they formed integral parts of a consistently-designed pioneering railway.

By the 1870s the growth of traffic, especially at the London end of the route, necessitated the widening of the line from two to four tracks. This was carried out in two stages, from London to Taplow in 1875-84 and from Taplow to Didcot in 1890-3. By the time the line was widened, the broad gauge was being phased out (the final conversion to standard gauge took place in 1892), and the design of the extended or new structures took this into account. However the designs were exceptionally sympathetic to Brunel’s original designs, in form and detail; also in the choice of materials, although engineering brick, seldom or never used by Brunel, began to make an appearance in 1890s. The engineers chiefly responsible for the widened lines, whose names appear on the surviving archive drawings, were William George Owen (1810-85), Lancaster Owen (1843-1911) and Edmund Olander (1834-1900).

Silly Bridge is an accommodation bridge constructed as part of Contract 4R on the section of the line between Reading and Steventon, which opened on 1 June 1840. The resident engineer for this section was John Hammond. Contract drawings survive illustrating a triple-arched structure with narrow side arches. Drawings also survive for widening the bridge c. 1890-3 as part of the quadrupling of the line from Taplow to Didcot. This was achieved by demolishing the north (Up) side arch and erecting a wider arch and new abutment in engineering brick to accommodate the relief lines. Since these works there have been no significant alterations.

Details

MATERIALS: local red brick for the original (south or Down side) portion of the bridge; GWR red and purple engineering brick for the 1890s portion (north or Up side). English bond. Stone coping.

DESCRIPTION: from the south (Down) side) to the north (Up) side: the c. 1840 portion has a curved wing wall/abutment, a 17ft 6in [5.2m] side arch and the taller original central arch with a span of 30ft [9m]. The tapered piers have a single tapered transverse arch each. The c. 1893 portion commences with a widening of the north pier, from which springs an arch with a 26ft 6in [7.9m] span and finishes with curved abutment/wing walls. The two contrasting phases of brickwork are clearly delineated by a straight joint all the way from the foot of the northern pier to the coping, but otherwise all detailing is entirely consistent across both parts, including impost bands, roll-moulded string course, the original stone coping stones (reused on the 1893 portion) and terminating piers. The only exception is the parapets of the 1893 portion, which step up twice towards the higher cutting on the north side. Some engineering brick patching to the inner faces of the parapets, and recent wire mesh fencing attached to the coping.

Silly Bridge stands in a rural landscape in the North Wessex Downs Area of Outstanding Natural Beauty .

Sources

Books and journals
Bourne, J C, The History and Description of the Great Western Railway, (1846)
MacDermot, E T, A History of the Great Western Railway, (1927, revised ed. 1964)
Pugsley, A, The Works of Isambard Kingdom Brunel, (1976)
Vaughan, A, A Pictorial Record of Great Western Architecture, (1977)

Other
Alan Baxter & Associates, The History and Significance of the Great Western Main Line , 2012,
Network Rail, Network Rail National Records Centre Roll Number 13017 (4270), 16348 (596),
Kinchin-Smith, R, Crossrail Technical Assessment of Historic Railway Bridges , 2005,

End of official list entry

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