A Study on a Seismic Behavior of embedded Pipeline Under an Earthquake

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This study deal with a seismic behavior of an embedded pipeline subjected to incident wave as for a three dimensional easto-dynamic problem. The incident wave is taken to be a plane SH wave in the form of a Ricker wavelet whose front is slanting to the axis of the cylinder. These problems were analyzed by the use of solutions of three dimensional wave equations of a cylinder, a boundary layer and an elastic medium having a cavity, so as to satisfy the boundary conditions of the elastic medium, the boundary layer and the cylinder. These solutions are easily obtained by mean of Fourie-Hankel transforms with respect to three direction of space coodirates, and the time direction. The cylinder and the elastic medium are models of the pipeline and the ground respectively. And the boundary layer is also model of different layer from the cylinder or the elastic medium, surrounding the pipeline.The numerical caluclations are carried out for various cases of the eastic constant ratios for elastic medium, boundaty layer and pipe ; the angle between an axis of pipe and the direction of incident wave ; and the period of incident wave.The results are presented in the from of a radial displacement diagram of the horizontal plane, including the diametrical plane of pipe ; and a tangential stress distribution diagram to the inner and outer surface of the pipe and those results are as follows :1) At the short period of incident wave, the reflected waves appear in the incident side of elastic medium and the large local tangential stresses occur in the cylinder, but the displacements of cylinder are very small.2) At the long period of incident wave and in case of relatively large elastic constant of the boundary layer, the displacements of cylinder is almost same as the displacement of incident wave, and the overall stresses occur is the cylinder.