Uncertainty in reliability of thick high strength pipelines with corrosion defects subjected to internal pressure

This paper assesses the uncertainties in the structural reliability levels of thick high strength pipelines with active corrosion defects subjected to internal pressure. A general burst strength model and other applicable to thick high strength pipes are adopted and their predictions uncertainty over a wide range of corrosion defect depths is assessed by Monte Carlo simulation. A 3-parameter lognormal probability model is adopted to describe the uncertainty in the burst pressure. Global and corrosion defect depth dependent model uncertainty factors are derived by comparing the predictions of the burst strength models with burst test data of corroded pipes. Burst failure limit states are formulated in terms of the burst strength models and corresponding model uncertainty factors. Linear and nonlinear corrosion models are adopted to describe the growth of corrosion defects. The uncertainty on the safety levels of pipelines due to the uncertainty on the corrosion defect, corrosion growth model and reliability algorithm is assessed. The results presented for the two strength models provide insights on the adequacy of a thick high strength burst model for probabilistic applications in comparison with a general burst strength model.