Application of Structural Reliability Analysis to UHB Pipeline Design

The detailed design of pipelines susceptible to upheaval buckling (UHB) has been characterized by a wide range of industry approaches, especially in relation to selecting safety factors. DNV recently published the draft of their HT/HP design code (RP-F110), which aims to codify and unify approaches to this aspect of design. Sensitivity analysis using Structural Reliability Analysis (SRA) methods highlights the sensitivity of rock cover requirements to a small number of key parameters. Several of these, including: Young’s Modulus; coefficient of thermal expansion; rock cover height; and rock uplift resistance factor have very poor published public domain statistically measured information on mean and variance. It is clear that the early identification in a project of the potential cost benefits associated with an SRA approach maximizes the potential to collect good project-specific statistical data. The clear benefit is an improvement in overall safety by ensuring a more uniform probability of failure along the pipeline which meets target reliability levels.