Fatigue reliability of single-sided girth welds in offshore pipelines and risers accounting for non-destructive inspection

The study aims to assess the fatigue reliability of single-sided girth welds in offshore pipelines and risers based on crack propagation analyses accounting for Non-destructive Inspection (NDI). The initial crack size distribution at the weld root is determined through the calibration of the crack propagation analyses to the S–N data. The effect of NDI, which is carried out immediately after welding, on the initial crack size distribution is modelled. The initial crack size distribution can be significantly changed by NDI and possible repair, and should be updated. The effects of the misalignment and NDI on the fatigue strength and reliability of single-sided girth welds are investigated based on the probabilistic crack propagation analyses. It has been shown that based on existing stress intensity factor solutions, the effect of the misalignment on the fatigue strength is not as significant as that recommended by the fatigue design code. The effect of the acceptance criterion of the initial crack depth on the fatigue strength and reliability can be quantified based on the updated initial crack depth distribution.