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Railway Structures
Types of Bridge

There are many different bridge designs, but all bridges adopt one of three basic structural forms, even though shape, size and construction materials can vary considerably.

Arch

Brooklands Road bridge Brooklands Road bridge, Weybridge has three segmental brick arches, photographed on 10th May 2009.

photograph by Gregory Beecroft

An arch remains in position because it is under compression. Gravity forces the bricks or stones forming the arch rings together. However, if the arch fractures, so as to hinge, it is likely to fail quickly. Different types of arch are described in the Brick pages.

Beam

Gun Lane bridge carries the Chatham line at Strood and is a typical simply supported beam bridge, in this case with plate girders, photographed on 10th April 2009.

photograph by Gregory Beecroft

Gun Lane bridge, Strood

A beam bridge comprises members supported from fixed points. The beam has to be sufficiently strong to resist downward force, resulting in compression on the top edge and tension in the lower one. Most such bridges on railways are simply supported ones, where the beams span between two fixed points. However some have continuous beams with multiple supports. A cantilever bridge is one where the beams are unsupported at the ends.

Suspension

A suspension bridge is one where the deck is supported from above by cables. This form of bridge is rarely used for railways. Lyne bridge, Chertsey, a cable stay structure, is an unusual exception.

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This page was created 3 January 2010

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