Response Of Underground Pipeline To Random Ground Motion

Seismic response of underground pipelines is usually calculated by wave propagation theory, in which stochastic spatial variation of ground motions is underestimated. The data recorded at dense instrument arrays has confirmed the strong randomness in space and time of seismic ground motions at different stations and the non-obvious wave passage. Hence it is of importance to investigate seismic responses of underground pipeline to random ground motions both in theory and engineering. The series solutions of responses of underground pipeline to multi-support excitations are given by Qu Tie-jun and Wang Qian-xin, in which pseudo-static and dynamic responses of underground pipeline could be analyzed respectively, and the pseudo-excitation method is established by Lin Jia-hao and Zhang Ya-hui for random vibration of structure, so random vibration analysis of underground pipeline by pseudo-excitation method will be mainly solved in this paper.Seismic ground motions are considered stationary stochastic process, the pipe rests on elastic foundations in uniform medium, the seismic input is stationary cross-PSD matrix, and responses of underground pipeline to stationary random ground motions are solved by pseudo-static method. The effect of spatial coherence of seismic ground motions on pipeline is mainly analyzed, the results show that the partial coherence of seismic ground motions could produce excessive stresses, it is suggested that the partial coherence of seismic ground motions should be considered, and coherence models should be chosen cautiously.Seismic ground motions are considered non-stationary stochastic process, the pipe rests on elastic foundations in uniform medium, the seismic input is time-varying cross-PSD matrix, and the responses of underground pipeline to non-stationary random ground motions are solved by pseudo-static method. The impact of locality effect on pipeline is mainly analyzed, the study shows that the locality effect has little impact on pipeline, it is suggested that locality effect can be neglected in practice.Seismic ground motions are considered stationary stochastic process, the pipe rests on elastic foundations near the interface of two media, pseudo-static responses are only considered, and responses of underground pipeline through two media to stationary random ground motions are solved by the basic random vibration theory and the pseudo-static method. The effect of the sudden change of media properties on pipeline is mainly analyzed, the results show that the pipeline near the media interface is easily damaged, and the larger soil differences, the more easily damaged pipeline.Seismic ground motions are considered stationary stochastic process, based on Mindlin solution and dynamic basic solution of elastic half-space, static stiffness and dynamic stiffness of foundation are obtained respectively, and then responses of underground pipeline in uniform medium to stationary random ground motions are solved by pseudo-static method. The study shows that due to low-frequency properties of auto-PSD of ground displacements, dynamic stiffness of foundation can be replaced approximately by the static one.