Reliability-based fatigue and fracture mechanics assessment methodology for offshore structural components

Abstract The first major offshore oil and gas production facility went into service in the North Sea over two decades ago. Offshore structures in hostile environments like the North Sea are subjected to time-dependent local damage such as corrosion and fatigue. To ensure safe operations, the integrity of these components needs to be maintained in service. This is achieved by carrying out planned non-destructive inspection coupled with structural integrity assessments. The inspections are not an entirely reliable process, however. There are also many uncertainties involved in the fatigue integrity calculations. In order to take these uncertainties into account, reliability-based assessment can be used. This paper summarizes the recent development of reliability-based fatigue initiation and fracture mechanics (crack growth) analyses for the in-service assessment of the integrity of offshore structural components. The techniques are illustrated with two specific forms of structural connection: welded tubular joints and threaded (screw type) joints. Related practical issues, including the reliability of non-destructive inspection (NDI) and the considerations of targeting maintenance resources, are also discussed.