Elastoplastic stress–strain analysis of buried steel pipelines subjected to fault displacements with account for service loads

Abstract

This paper presents an analytical model for stress–strain analysis of buried steel pipelines subjected to active fault displacements, accounting for internal pressure and temperature variation Δ T (a difference between the operational temperature and the temperature of pipelay). Along with the longitudinal stresses and strains arising from combined bending and tension due to fault displacements, additional hoop and axial stresses and strains resulting from the internal pressure and temperature variation are taken into account within a two-dimensional elastoplastic model based on the plastic flow theory. The interaction of the pipeline with the surrounding soil is modeled in axial and transverse directions using bilinear soil springs. The analysis is performed iteratively as a series of elastic solutions using a secant modulus of the pipe steel. The validation of the proposed model is performed through comparison of the obtained solutions to the results of numerical simulations of the finite-element beam-type and shell-type models in the finite-element software ANSYS 12.1. It is shown that incorporating the two-dimensional elastoplastic approach within the analytical structural model of pipeline at active fault crossings provides good correspondence to the numerical results obtained with the finite-element model for various service conditions and a range of fault intersection angles.