Adam Viaduct

About

The Adam Viaduct is a grade II listed concrete underbridge in Wallgate, Wigan. The bridge, constructed in 1946, is the earliest 'post-tensioned' prestressed concrete railway bridge in the United Kingdom, with only some examples in Switzerland being earlier. It is bridge number 54 on the Kirkby branch line and is at a line distance of 18 miles 1,032 yards (29.91 km).

The bridge was constructed as a test case, to see if prestressed concrete construction was feasible for rail projects in the UK, by the LMS railway company, and designed by their chief civil engineer William Kelly Wallace. The beams used were prestressed using the Freyssinet system, in which concrete is precast with stressed high-tensile-strength metal tendons, which consist of multiple steel wires, running down the length of them. In construction, the beams internal rods are tightened and tied together so, under live load, they act as one. The LMS developed this system in the 1930s, and prestressed beams were first used for emergency repairs during World War II, but the Adam Viaduct first to use them for a full-scale project. The benefits of the system were found to be that it was quicker...