Ensuring Stability for all Stages of Barmouth Viaduct Metallic Spans Replacement

Barmouth Viaduct is a 150-year-old Grade II* listed structure and a significant landmark on the north-west coast of Wales in the UK. The bridge is an access route, carrying a single-track railway, a public footpath and cycleway over an estuary. The 820 m long structure consists of the longest timber railway bridge in Great Britain and five metallic spans over the navigation channel. In 2020 it was recognised that the metallic spans were life expired and a design and build contract was awarded for their replacement. An innovative method for the reconstruction of the structure was needed as traditional methods using jack-up barges and cranes were not cost-effective and introduced additional risk to the project. This paper covers the technical aspects related to the detailed design of the construction method for new metallic spans including the main temporary works that were adopted to ensure stability at all stages of the works and were key to the successful delivery of the heritage structure.