Probabilistic Assessment of Pipeline Collapse: Combined Loading

Buckling is known as one of the most important factors on maintenance cost of offshore pipelines. Based on the size of deformation, buckling is divided in two classes; local buckling and global buckling. Global buckling occurs due to large gradient in pressure and temperature of pipeline. Assessment of local buckling is performed in two ways; considering external pressure as only effective parameter on pipeline buckle behavior, considering combined effect of external / internal pressure and axial force. In this paper, integrity of a pipeline in South Pars against local buckling is assessed in terms of probability of failure for different water depths. For getting more accurate results, geometry parameters and loading parameters are modeled as uncertainty parameters. Accuracy of First-Order Reliability Method is evaluated by comparing with Monte-Carlo Sampling (MCS) method. In order to investigate effect of each parameter on POF of the pipeline, sensitivity analysis using alpha index is carried out. It is concluded that using Weibull distribution for deep waters can lead to better results than modeling with Normal distribution. Also, it is concluded that internal pressure and pipeline wall thickness are the most effective load and capacity parameters on the POF of the pipeline against local buckling.