Management of the Severn Bridge Suspension Bridge

The M48 Severn Bridge is a 988 m span suspension bridge carrying the M48 motorway across the River Severn in the UK. The bridge is substandard to current UK assessment codes but is permitted to continue in operation on the basis that application of the Highways Agency document, BD79, which allows a risk-based management approach to bridge operation, indicates the risk presented is acceptable given the mitigation and monitoring in place. A key aspect of the work involved in verifying that the bridge can remain in operation is undertaking continuous structural assessment, taking into account the results of previous cable intrusive investigations and data from the various continuous monitoring systems. This paper discusses the determination of the main cable strength allowing for its deterioration to date. It also discusses determination of the Bridge Specific Assessment Live Load model, used for the bridge assessment, from Weigh in Motion (WIM) data.