Reliability measures for buried flexible pipes

Abstract

The safety of infrastructure facilities such as buried pipelines is the primary objective of engineering design. An improved measure of safety and reliability of these structures can be obtained with concepts of probability. The assessment of safety involves uncertainties at various stages, such as testing, design, and field installation and operations. This paper presents a reliability analysis to estimate the deflection (cross-sectional ovalization) and buckling response of buried flexible pipes, considering uncertainties in the design parameters. The need to consider variations in design parameters, such as soil modulus and bulk density of the fill, and the influence of correlation between soil modulus and bulk density in the estimation of reliability is emphasized. It was observed that reliability index decreases with an increase in the coefficient of variation of soil modulus and bulk density of the fill and increases with increase in correlation coefficient between the variables. It is possible to obtain a central factor of safety (CFS) value on the basis of the target reliability and variations in the design parameters. The use of reliability-based considerations is illustrated with two typical simple cases of buried pipe installations.Key words: reliability measures, buried flexible pipes, deflection (ovalization), buckling, variability, safety.