Monitoring and Maintenance of the Boyne Viaduct

The central steel span of the Boyne Viaduct in Drogheda, Co. Louth, was constructed in 1932. At the time of construction, the bridge was not expected to have a design life in excess of 76 years. It is therefore vital that the... [ view full abstract ]

The central steel span of the Boyne Viaduct in Drogheda, Co. Louth, was constructed in 1932. At the time of construction, the bridge was not expected to have a design life in excess of 76 years. It is therefore vital that the structure undergo a robust maintenance strategy in order to verify the ongoing performance in terms of reliability with respect to both the Ultimate Limit State (ULS) and the Fatigue Limit State (FLS). Global and localised 3D Finite Element modelling was used in conjunction with a reliability analysis of the structure in order to design a monitoring strategy. A combination of strain gauges and accelerometers were installed with the strain gauges being placed on the rail bearers and cross beams at sections which were expected to be critical both at ULS and FLS. Finite Element Model calibration from measurement allowed recalculation of the reliability index with lower uncertainties, resulting in a 48% increase in reliability. A reliability based fatigue analysis was also carried out at the sensor locations in order to calculate if sufficient reliability is provided on a yearly basis. The results showed that the most critical monitored section will have a minimum FLS reliability index of 9.3 after 150 years of service. The results of the analysis alleviate any safety concerns regarding the monitored locations of this iconic structure.