Reliability Analysis of Deflection of Buried Flexible Pipes

Abstract

The in situ behavior of buried flexible pipes is considerably influenced by uncertainties in external load, pipe, and soil properties. To take care of the uncertainties, while the conventional design methodology incorporates conservative factors of safety, it is desirable that these aspects of variability be incorporated in the design. In this paper, uncertainties in calculation of pipe deflection are reviewed. Soil stiffness and load are considered as random variables. Reliability assessment of deflection of a typical pipe section with typical soil properties is conducted using the point estimate method with respect to two reliability measures, central factor of safety and safety margin. Within the framework of analysis, results show that for flexible pipes, the conventional tolerable deflection limit of 5% of diameter of the pipe with respect to a factor of safety of 4 is conservative.