Application of subset simulation in reliability estimation of underground pipelines

Abstract

This paper presents a computational framework for implementing an advanced Monte Carlo simulation method, called Subset Simulation (SS) for time-dependent reliability prediction of underground flexible pipelines. The SS can provide better resolution for low failure probability level of rare failure events which are commonly encountered in pipeline engineering applications. Random samples of statistical variables are generated efficiently and used for computing probabilistic reliability model. It gains its efficiency by expressing a small probability event as a product of a sequence of intermediate events with larger conditional probabilities. The efficiency of SS has been demonstrated by numerical studies and attention in this work is devoted to scrutinise the robustness of the SS application in pipe reliability assessment and compared with direct Monte Carlo simulation (MCS) method. Reliability of a buried flexible steel pipe with time-dependent failure modes, namely, corrosion induced deflection, buckling, wall thrust and bending stress has been assessed in this study. The analysis indicates that corrosion induced excessive deflection is the most critical failure event whereas buckling is the least susceptible during the whole service life of the pipe. The study also shows that SS is robust method to estimate the reliability of buried pipelines and it is more efficient than MCS, especially in small failure probability prediction.

Approximate Method to Evaluate Reliability of Complex Networks

“…The methods of network reliability evaluation based on SDP algorithms fall in the NP-hard category and, consequently, are difficult to apply for very large networks, such as social networks. In these cases, other techniques for approximate evaluation can also be applied, especially the Monte Carlo simulation (see, for example, [24][25][26][27]). Even so, the methods based on SDP algorithms are still necessary for the validation of simulation programs.…”

Structural robustness assessment of corroded buried pipes

“…The bending of a buried pipeline depends on the surface loads acting on the pipe wall. The allowable bending stress is the long term tensile strength of the pipe material and the allowable strain of a flexible pipe is from 0.15% to 2% [33]. Actual bending stress σ and bending strain can be calculated using eqn (18).…”

System‐level reliability sensitivity analysis by using weighted average simulation method

“…Another limitation of the presented method is that the reliability sensitivity analysis based on the line sampling requires an accurate estimation of the optimal direction, while the reliability analysis based on the line sampling does not have this requirement . Application of subset simulation and decomposition methods for obtaining reliability and RBS results has received due attention . However, as well as the score function approach, estimation of sensitivities by these approaches requires derivation of PDFs and satisfying the regularity conditions to provide results.…”