Longitudinal Seismic Response of Underground Pipelines Subjected to Multiple-Supported Random Ground Excitations

Abstract

For long-span structures, such as long bridges and underground pipelines, the loss of correlation of ground movements during an earthquake should be taken into account for seismic analyses. In this paper, longitudinal seismic responses of underground pipelines, which are modeled as distributed mass pipelines with fixed-fixed ends, are derived with a pseudo-excitation method. The seismic excitation is considered a random process and partially correlated. The root mean square (RMS) axial stresses and displacements are compared between pipelines with fixed-fixed and free-free ends. The effects of slenderness ratio and pipe thickness on the seismic responses are also investigated. The results show that the seismic response of fixed-ends and free-ends pipelines matches well when the slenderness ratio is large enough. On the contrary, the boundary conditions should be taken into account for short pipes or pipes with a large external radius. The RMS axial stresses at the midpoint of the pipes decrease with the increase of pipe thickness, and no significant difference is found between fixed-ends and free-ends pipes.