RIVER DEE VIADUCT - DESIGN

The River Dee Viaduct carries the single carriageway of the new Newbridge bypass across the deep valley of the River Dee in the County of Clwyd, North Wales. The topography and road alignment mean that the carriageway is about 60 m above river level and the tallest pier is 46.7 m high. Excavations up to 20 m deep were required for large concrete spread footings, with hollow rectangular reinforced concrete piers supporting the viaduct. The 348 m long superstructure has a single cell cross-section, with a straight-haunched elevation, and has spans of 55.5 m, 77.0 m, 83.0 m, 77.0 m and 55.5 m. The superstructure is of post-tensioned in-situ concrete, in segmental form, designed to be constructed by balanced cantilever methods. This Paper describes the history of the Newbridge bypass and of the adjoining Ruabon and Chirk bypasses, and the principal design considerations addressed during the feasibility, preliminary and final design stages of the River Dee Viaduct. The superstructure was constructed to an alternative design by the Contractor. This Paper concentrates on the design development and fundamental philosophies adopted to bring this interesting project through to construction.