Inspection and maintenance of Severn Bridge suspension cables

The Severn Bridge, completed in 1966, was the first suspension bridge to adopt a streamlined box girder deck that reduced the dead weight and improved aerodynamic performance. The 988 m span bridge crosses the estuary of the River Severn and is an important asset within the UK highway network. In 2006, the UK's Highways Agency, through the concessionaire Severn River Crossing plc, commissioned a programme of internal intrusive examination of the main suspension cables of the Severn Bridge with Faber-Maunsell/Weidlinger acting as consultants for the inspection. The information obtained during these investigations provided the basic data for use in a formal strength assessment of the suspension cables undertaken by Mott MacDonald, the UK government's representative for the Severn Crossings concession. Analytical techniques developed over the past 3 years have enabled the adoption of limit state principles for the assessment in line with UK practice. In addition, deterioration modelling has been developed to improve understanding of the current condition of the cables and to assist in the future management of the bridge. In parallel with the strength assessment, process maintenance management strategies have been developed and implemented that have enabled the continued safe operation of the bridge.