Seismic analysis of a buried operating steel pipeline with emphasis on the equivalent-boundary conditions

It is of fundamental importance in engineering design practice to accurately evaluate the structural response of buried pipelines subjected to seismic hazards, like landslides, lateral spreading due to liquefaction, and faulting, because these seriously threaten pipeline safety. The present paper investigates the seismic performance of a buried operating steel pipeline subjected to strike-slip faulting using the continuum finite element modeling approach and considering appropriate equivalent boundaries representing the interaction with the rest of the soil-pipeline system. The latter are derived analytically in terms of an axial spring expressed in function of the soil-pipeline nonlinearities, service loads like the internal pressure and temperature variation, pipeline unanchored length, cross-section area, and the different loading paths either in tension or compression. The obtained analytical and numerical results give a better insight into the mechanical behavior of the soil-pipeline system subjected to strike-slip faulting that induces overall tension in the pipeline under different levels of operating loads. The methodology described in this paper, including the formulation of the equivalent boundaries, can be applied to accurately and efficiently assess the seismic performance of operating buried pipelines subjected to strike-slip fault movement and similar permanent ground deformations (PGDs)