Reliability of Underground Pipelines Subject to Corrosion

Abstract

The present paper is concerned with estimating the reliability of underground pipelines subject to externally applied loading and to corrosion, either externally or internally, or both. This affects the strength of the pipeline in resisting the applied loads so that the reliability would be expected to decrease with time. Corrosion is a phenomenon about which there is a great deal of uncertainty. One way of allowing for this is through probabilistic modeling of the material loss as a nonlinear function of time. This approach is explored in the present paper, using a nonlinear function first postulated for atmospheric corrosion. This model is incorporated into expressions for stress resulting from externally applied loading and internal pressure to provide a limit state function expressing the boundary between survival and failure of the system. The probability of system failure is then evaluated using techniques developed for structural reliability analysis.