Selection of Lateral Artificial Boundary Distance and Its Influence on the Site Seismic Responses Analysis

摘要

Numerical simulation has been used to research the problem how to select the lateral artificial boundary distance for the uniform site and layered uniform site. The main factors and its influence on the seismic analysis results have also been studied. The main results can be summarized as following: the ratio between one side lateral artificial boundary distances and the soil depth (L/h) is the key parameter to affect the numerical results. But the error of the finite element method does not always decrease with the increasing of the L/h, in some range of L/h, the accuracy decreases as the L/h goes up. The ratio L/h corresponding to steady value are not affected by those parameters such as the site shear velocity and damping ratio and the excitation frequency, but the spectrum characteristics of the seismic wave have obvious effect on the calculating results, especially for the free-field boundary condition. For the one-dimensional site, tied degrees of freedom boundary condition achieved the best results, followed by free-field boundary condition and the viscous boundary condition is less suitable for seismic responses analysis of site. Whatever boundary conditions, we can get the steady results under the ratio of L/h larger than some value. The ratio of L/h usually can be moderately reduced for the layered uniform site than the uniform site.