Incident Wave Angle Effect on the Behaviour of Bent Embedded Pipe

Abstract

Pipelines are important lifeline facilities distributed over a large area and they generally encounter a range of seismic hazards and soil conditions. Seismic wave propagation and its incidence affect the performance of buried pipes. Due to considerable stress concentration and additional flexural strains in the elbow region of pipelines, consideration of this area is important. This subject has been studied in the presented research. For this purpose, three dimensional finite element models have been employed. In these models beam elements and nonlinear spring elements are used for simulation of the buried pipelines and soil-pipe interaction, respectively. Moreover, an equivalent boundary condition has been used at the end of each leg of the pipe that simulates its infinite length more accurately. Incidence of waves with different angles causing time lag in vibration of different points has been studied as an important influencing parameter on a pipeline system. Also, the effect of soil type on seismic response of the buried pipe in bent area is considered in this paper. It is concluded that a direct relationship exists between larger soil stiffness and increasing axial elbow strains. Also inclined wave propagation multiples the elbow response compared to vertical propagation of waves. The peak response happens when waves travel parallel to a pipe leg.
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