Seismic response and behavior of buried continuous piping systems containing elbows

This thesis examines the seismic behavior of buried pipe containing elbows. In particular, an analytical solution is provided for a piping system containing a 90° elbow that allows for possible inelastic soil behavior in the direction of the ground movement. Existing analytical techniques only allow inelastic soil behavior along the longitudinal leg of the pipe elbow, that is, the leg parallel to the direction of ground movement. The formulation provided herein allows for soil slippage along the transverse leg as well.; The presence of an elbow acts as a structural discontinuity with respect to the behavior of a straight section of pipe. For small to moderate diameter pipelines, straight sections typically are more susceptible to axial effects than to bending effects. Consequently, buried piping systems (i.e., those in a horizontal plane) are most susceptible to Rayleigh Wave Propagation (WP) which induces axial strain in the direction of propagation. In terms of Permanent Ground Deformation (PGD), longitudinal PGD is also of particular interest since it can induce significant axial strains.; For moderate to large WP (Rayleigh wave) ground strain, the elbow acts as a stress riser compared to the response of continuous pipe, with the majority of strain being flexural. Elbow strain values remain below ground strain values, with the lag increasing with increasing ground strain. This effect is only marginally over predicted by existing formulations, but increases with increasing ground strain.; For longitudinal PGD, it is shown that the distribution of loads and displacements within the PGD zone is sensitive to the location of and specific type of structural discontinuity (i.e., pin, free end or elbow). Existing formulations consider only an elbow discontinuity and inelastic soil behavior only along the longitudinal leg. For a "flexible" device (i.e., elbow or free end) outside of the PGD zone, the maximum tensile strain in the tensile region of the straight section increases while the maximum compressive strain in the corresponding compression region of the straight section decreases. Furthermore, the flexural strain at an elbow increases the closer the elbow approaches the PGD zone, and consequently acts as a stress riser.