|A semi-elliptical arch has a significant advantage over
round-headed ones, by giving much better headroom over the full width of the
bridge. Therefore, a semi-elliptical arch could be narrower or lower than a
round-headed one, while still giving adequate clearance at cantail level for
trains to pass below. They were more complicated to build, because an ellipse
is less easily traced than a circle. Semi-elliptical arches create greater
thrust against abutments, but that is of no great concern if the bridge spans a
cutting or is contained by an earth embankment. Not all arches have the shape
of a true ellipse. In order to make setting out easier, three-centred arches
have small-radius circular arcs at the corners and a larger-radius circular arc
across the centre.
This semi-elliptical arch bridge is at the country end of Birchington-on-Sea station. A modern footbridge has been provided on the far side of the bridge, so that the full width of the old bridge can be used by motor vehicles. The parapet has been rebuilt.
This bridge carries a footpath over the railway at Falmer and is typical of those found on the Coastway lines and Brighton main line. It also has rebuilt parapets.
This bridge carries a minor road over the Exmouth branch just north of Lympstone and is close to original condition.
This bridge, which carries the access to the golf course at Bearsted, has a semi-elliptical central arch and round-headed side arches. This is a fairly common design, allowing the narrower side arches to have the same spring and crown heights as the wider central arch.
Midhurst Road bridge, Liphook, has three arches, but all are elliptical.
Semi-elliptical arch bridges are found particularly on older lines, but segmental arches became more usual. The South Eastern Railway had changed to segmental arches by 1850. Semi-elliptical arches are found on its original main line from Redhill to Dover (though many have been altered) and between Ashford and Canterbury. However, there are none on the lines to Hastings or later routes. On London, Chatham & Dover lines semi-elliptical arch bridges are found principally between Newington and Broadstairs, though there are some on the Maidstone East line. There are many semi-elliptical arches on the southern part of the Brighton line, which remains double track, and quite a few on the Coastway routes.
The London & South Western Railway was building semi-elliptical arch bridges in quantity, well after the other southern lines had abandoned the design. There are three over the Guildford New Line between Hampton Court Junction and Oxshott, and one at Bookham (pictured above), all built in 1884.
Several multi-span examples were built when the Main and Windsor lines were quadrupled during the 1880s, including Heathfield Road bridge, over Clapham cutting, and Hook Heath bridge, Woking. Two attractive bridges between Point Pleasant Junction and Putney have a centre semi-elliptical span over the fast lines flanked by single-track round-headed arches over the slow lines.
Rosendale Road bridge was one of several that the London, Chatham & Dover Railway had to build to an ornate design in order to meet the requirements of the Trustees of Alleyn's College. It carries the railway from Herne Hill to Tulse Hill. The fine yellow and red bricks used in this intricate design contrast with the rough London stocks used on the rest of the viaduct. This is another bridge that has a semi-elliptical arch flanked by round-headed side arches.
Old Shoreham Road bridge, on the Cliftonville Spur from Preston to Park to Hove, is another with a semi-elliptical main arch and round-headed side arches. In this case the crown of the main arch is slightly lower than those of the side arches. Steel bracing, painted red, has been added to the side arches. The portal of Cliftonville Tunnel can be seen through the bridge.
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This page was created 9 April 2010