Analysis of terrain effect on the properties of ground motion

The explicit finite element analysis method combined with the artificial viscous-elastic boundary theory based on the platform ABAQUS is performed to evaluate the terrain effects on ground motion (such as the response spectrum, peak acceleration, peak velocity and peak displacement), and the influence of the terrain width on its amplification effects is studied. The results show that the ground motions on the platform are affected most seriously by the topography; in the zero damping conditions, the spectral ratio curves present the characteristics of double peaks,with their values being a higher value of 1.6 in the long period range of 0.8—0.9 s and exceeding 2 in the high-frequency range of 0.08—0.09 s, and the maximum ratio appearing at the midpoint of the platform. For the slope section, as to most natural periods of response spectrum, the spectral ratios of the vertices are higher than the other surface points on theslope.Inaddition,inthenatural period beyond 0.4 s, the spectral ratios of the spatial points on the slope show some regularity: the closer to the vertex the observation point, the greater the spectral ratio.Spectral ratios of different observation points on the bottom change between spectral ratios corresponding to basic foot point and those to the boundary point,ortheartificial boundary point, which is obvious in different frequency bands. The width of terrain imposes significant influence on its amplification effects on high-frequency componentsofgroundmotion.However, such influenceislimited in some range of width, and with the increase of width, the influence of width on the topographic amplification effects becomes weak. In addition, the width of terrain influences the amplification effect on the peak acceleration of ground motion to some extent, while its influences on the amplification effects on thepeakground velocity and peak ground displacement are not distinct.