Built in 1856 — and rebuilt in 1915 — the 51-span Arnside Viaduct carries the Carnforth to Whitehaven railway over the River Kent estuary at a point close to Morecambe Bay. Its deck had suffered considerable deterioration and Network Rail decided to replace it. Our transport engineers undertook a Grip Stage 5 (Form B) design for the superstructure, working closely with contractor May Gurney.
Value engineering of the Form A scheme had resulted in a design that involved significant structural interaction between the deck, substructures and running rails. As part of our work, we developed an analysis of this design using a series of non-linear connections between the elements to provide information on the expected stresses and bearing loads. The loads imposed by the marine environment and the topography of the site were also taken into consideration.
The scheme involved the removal of the 476m viaduct’s entire deck. New bearings were fixed to the top of the existing piers which support two steel battle deck units. Continuously-welded rails are fastened directly to each of the decks with no ballast, flanked by steel walkway units. New sill beams and anchor slabs have been installed in the abutments.
The railway was closed for a 16 week period while the works took place. The new system provides a quieter and smoother passenger experience and is expected to decrease the overall journey time on the line.