Response Of Buried Elbow Pipeline Under Oblique Incidence Seismic Wave

The buried pipeline is high vulnerable in earthquake, as the one of main four transmission system, the pipeline or buried pipeline plays a more and more important role for energy transportation, like oil, natural gas. so, it is very important for healthy economic and social sustainable development how to keep the pipeline system safety. Unlike the traditional experimental researches, With the rapid development of computer simulation technology, it has provided an economical and feasible method for the seismic research of underground pipelines. At present, the vertical incidence of seismic wave is considered in the seismic response analysis of underground structure, although the assumption is not consistent with the engineering practice in most of cases, particularly for the study of large volume and long linear structures, it is more accurate to consider the effect of oblique incidence of seismic wave. For this reason, based on the elastic-wave theory combining the finite element method with viscous-spring artificial boundary condition, the input method of the oblique incidence of seismic waves are realized. Then the effect of the oblique incidence of seismic waves on the buried elbow pipeline and related factors are studied. Herein, the main researches and conclusions are concluded as follows:Firstly, the elastic wave theory that combines finite element method with viscous-spring artificial boundary condition is introduced. The equivalent seismic nodal loads calculated by MATLAB are imported into ANSYS. Then the input method of the oblique incidence of seismic waves are realized by using APDL language. The numerical results of a half space proved that the model and the method was reliable and could be used to simulate the dynamic response of soil and buried structure.Then, the seismic responses of buried pipe elbow under vertical incidence and oblique incidence is discussed respectively. The simulation results shows that oblique incidence of seismic waves have a significant influence on the horizontal displacement and velocity, despite of negligible impact on the vertical response; It can be also found that the stresses distribution of the elbow vary clearly and have an obvious increase at some key nodal points with increasing incident angel; Besides, compared with vertical incidence, deformed shape of buried elbow section shows the trend of a gradual flattening with increasing incident angel.Lastly, several key factors affecting the seismic responses of buried elbow pipeline are discussed with the same incident angel but different seismic waves. The simulation results also shows that the frequency spectrum of seismic wave has a significant effect on the seismic response of the buried pipeline; The smaller the dynamic elastic modulus of soil is, the more obvious the delay effect and the bigger displacement response is; The smaller the soil Poisson’s ratio is, the bigger the stress response is; The more shallow the buried pipeline is, the smaller the stress response is; The smaller the pipe thickness and the friction coefficient between the pipe and soil is, the greater the displacement, velocity and acceleration response is.It has been proven that the study in this dissertation can successfully simulate earthquake damage characteristics of buried elbow pipeline under earthquake invading, and the results from this paper could be used to improve the resisting seismic performance of buried pipeline system.