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Maidenhead Railway Bridge
River Thames, west of Slough, Buckinghamshire, UK
Maidenhead Railway Bridge
associated engineer
Isambard Kingdom Brunel
Sir John Fowler
date  1837 - 1839, 1890 - 1893
UK era  Victorian  |  category  Bridge  |  reference  SU900810
ICE reference number  HEW 30
photo  Jane Joyce
To carry the Great Western Railway across the River Thames between Slough and Maidenhead, Brunel had to balance the need for navigational headroom with his own stringent targets for railway gradients. He produced a Grade I listed masterpiece — a bridge with two spectacular semi-elliptical brick arches that were the flattest ever constructed. The bridge was later widened and still carries modern rail traffic daily.
On 7th March 1833, Isambard Kingdom Brunel (1806-59) was appointed engineer for the double track railway between Bristol and London. On 31st August 1835, the Great Western Railway Act was passed and construction began in 1836. Brunel chose to use broad gauge (2.14m, 7ft 0.25in) rail tracks and to keep the route as level as possible, claiming higher travel speeds and increased passenger comfort.
At Maidenhead, his red brick bridge over the River Thames had to accommodate the necessary navigational clearance at the same time as maintaining the even gradient (1 in 1,320 here) that he had set out to sustain for the whole railway. Using calculus principles, he designed the flattest bridge arches yet built, and they are thought still to hold that honour.
The bridge is some 235m long and was originally 9.1m wide. Its structure is visually symmetrical about the central river pier, which is founded on an existing island midstream. The two main arches are semi-elliptical, each spanning 39m with a rise of only 7.4m.
The approach viaducts each have four round-headed flood arches. The shorter arches nearest the river bank span 6.4m and the six flanking arches each span 8.5m. The identical elevations have Doric pilasters between the river and bankside arches and corniced parapets throughout. The deck is of stone slabs.
As with the other large bridges on the line, Brunel reduced the forces acting through the brickwork by using internal longitudinal walls and voids, lightening the superstructure above the arches and reducing the bridge's overall weight.
The innovative low-rise river arches attracted much controversy concerning their stability. Critics appeared to have been right when the timber centring used in construction of the arches was eased. On the eastern arch, the three lowest rings of brickwork began to settle, separating from the body of the arch over a distance of between 7.6m and 9.1m. However, the problem resulted from the mortar not being fully hardened and appeared worse on the bridge spandrels than midway under the arches. In July 1838, the contractor William Chadwick admitted he was to blame.
Remedial works were carried out, after which, in October 1838, the centring was again eased but left in place over the winter. The centring was eventually destroyed in a storm during autumn 1839 — but the arches stayed up, confounding the critics and vindicating Brunel.
Maidenhead Railway Bridge opened on 1st July 1838, and the Great Western Railway was completed in 1841.
In 1844, the famous artist Joseph Mallord William Turner (1775-1851) painted Rain, Steam and Speed – The Great Western Railway, showing a locomotive crossing Maidenhead Railway Bridge. It is now in the National Gallery (TQ299805) in London.
By the 1870s, the escalating volume of rail traffic necessitated widening the whole route from two to four tracks. Work began in 1875, with broad gauge phased out in favour of standard gauge (1.435m, 4ft 8.5in).
The railway from Taplow to Didcot, including the line over Maidenhead Bridge, was quadrupled in 1890-3. To accommodate the additional tracks, the bridge was widened on both sides by Sir John Fowler (1817-98), acting as consultant to the railway’s chief engineer Lancaster Owen (1843-1911).
The bridge's width was increased to 17.4m, parapet to parapet, and the top of the standard gauge rails laid at 11.9m above water level. The new bridge elevations were built to replicate the originals exactly.
It was found that the soffits of the principal arches had distorted slightly with the movement in the structure since completion. To compensate, the new brickwork was constructed marginally out of alignment with the old to maintain the arches as true ellipses, in accordance with Owen's wishes. The discontinuity can be seen from beneath the bridge.
To avoid differential settlement between old and new work, the foundation extensions were close piled, covered with a timber grillage and filled with concrete. The widened structure, presumably, is tied to the original internally with iron tie rods.
In 1950, the western half of the bridge was given Grade II* listing and in April 1985, the eastern half received the same designation. In July 2012, the entire structure was Grade I listed. In 1975, a commemorative plaque was erected on the bridge to mark European Architectural Heritage Year.
Resident engineer: John Wallis Hammond
Contractor: William Chadwick
Research: ECPK
reference sources   CEH LondIKB

Maidenhead Railway Bridge