引言结构的地震反应依赖于由地面传递到结构基底的运动的特征。对于支承在岩石或很坚硬地基上的结构,其基础运动基本上相同于自由场地运动,即指若该结构不存在时,基底处可能发生的运动。此时,由结构运动本身使地基土产生的变形与由地震应力波产生的变形相比,可以忽略不 Introduction The seismic response of a structure depends on the characteristics of the motion transmitted from the ground to the structural base. For a structure supported on rock or a very hard foundation, the basic movement is basically the same as the free-field movement, that is, the movement that may occur at the base if the structure does not exist. In this case, the deformation caused by the movement of the structure itself and the deformation caused by the seismic stress wave can be ignored.