thumb|Maidenhead Railway Bridge depicted by [[J. M. W. Turner in a painting from 1844]]

Maidenhead Railway Bridge, also known as Maidenhead Viaduct and The Sounding Arch, carries the Great Western Main Line (GWML) over the River Thames between Maidenhead, Berkshire and Taplow, Buckinghamshire, England. It is a single structure of two tall, wide red-brick arches buttressed by two over-land smaller arches. It crosses the river on the Maidenhead-Bray Reach, between Boulter's Lock and Bray Lock, and is near-centrally rooted in the downstream end of a very small island.

The Maidenhead Bridge was designed by the Great Western Railway Company engineer, the noted mechanical and civil engineer Isambard Kingdom Brunel. It was completed in 1838, but not brought into use until 1 July 1839. While it was being constructed, the innovative low-rise arches of the structure attracted considerable criticism and controversy, relating to their alleged lack of stability.

As a result, the centring for the arches was left in place until its destruction during a heavy storm in late 1839, despite which the arches stayed up, effectively vindicating Brunel's design. During 1861, dual-gauge track was installed across the structure, allowing both broad gauge and standard gauge services to cross it. During the late 1890s, the bridge was widened on either side to allow the structure to carry four standard gauge tracks, a task which was supervised by the civil engineer Sir John Fowler, who placed a high level of importance upon preserving the original design and appearance of the bridge.

Today, the Maidenhead Bridge forms a key crossing along the eastern section of the Great Western Main Line, allowing trains to travel to and from the line's terminus in the capital, London Paddington station. During the 2010s, the tracks across the structure were provided with overhead line equipment and associated infrastructure, to allow electric trains to use the route. The Maidenhead Bridge features in Rain, Steam and Speed – The Great Western Railway, painted by J. M. W. Turner during 1844, which is now in the National Gallery, London.

The bridge is approximate to the finish line of an annual day of rowing races, known as the Maidenhead Regatta. The Thames towpath passes directly under the right-hand arch (facing upstream), which is also known as the "Sounding Arch", due to its spectacular echo. During July 2012, the bridge was upgraded to a Grade I listed structure in light of its historical importance. To this day, the arches of the structure remain the flattest ever constructed.

The building of a bridge over the Thames at that location had to make provision for the necessary navigational clearance, so as not to unduly hinder the river shipping. According to author Paul Clements, the design selected by Brunel had been directly inspired by earlier experiments performed by his father, Marc Brunel, during 1832, which Isambard had financed. Isambard employed calculus principles in the designing of the bridge's critical semi-elliptical arches which supported the structure. Each arch has a span of , combined with a rise of only . The flatness of the arches was deemed necessary to avoid creating a raised "hump" on the deck of that bridge, which would have gone against Brunel's accommodation of the performance of the locomotives of the time, and his practice of maximising operational economy by building lines with flat or very gentle gradients (locally 1 in 1,320, which is less than 0.1 per cent), which had the benefit of reducing the running costs of the trains.

Construction

thumb|The echoing 'Sounding Arch' from the bank. The chamfered original centre section can be seen.

On 31 August 1835, the Great Western Railway Act was passed by Parliament, authorising the building of the line.

The innovative low-rise arches over the Thames became the subject of considerable controversy concerning their stability or purported lack thereof. To avoid any differential settlement between the old and new sections, the foundation extensions were close piled and covered with a timber grillage, before being filled with concrete. states:

<blockquote>

"The OHLE (Overhead Line Equipment) requires that supporting posts be founded on the bridge structure. These will be positioned so as not to disrupt the symmetry of the bridge. Three sets of masts will be fixed at the bridge supports and a further two sets will be fixed at the far ends of the bridge. The masts will be fixed such that they may be removed in the future without damaging the bridge as it stands today."</blockquote>

The report also states:

<blockquote>

"It is proposed that the OHLE over Maidenhead railway bridge will use masts with wires suspended from cantilevers, since these will be visually lighter structures than the gantries to be used along other parts of the route. The masts will however, have a significant adverse landscape impact: they will affect important views along the river and the character of the river corridor; they will affect the setting of the Riverside Conservation Area; and they will affect the setting of the listed railway bridge and the setting of the adjacent Grade I listed road bridge."

</blockquote>

As a means of reducing the visual impact of the electrification infrastructure on the historic bridge area, the possibility of adopting third rail electrification for that section of the line was proposed. However, following a study of that option, the use of a third rail was rejected.

See also

  • List of crossings of the River Thames

References

  • Newcomen Society information