地震作用下深厚土层-结构相互作用的高效分析方法

基于黏弹性边界和将场地反应转化为等效地震荷载的有限元直接法是目前进行地震作用下土-结构相互作用分析的常用时程分析方法之一。当土层厚度较深时，整个深厚土层-结构系统的有限元模型自由度数目较多，尤其对于三维问题，计算效率低。该文提出一种高效分析方法，即一维场地反应分析仍然针对整个深厚土层，在后续的土-结构相互作用分析中将土-结构计算模型的底面人工边界从深厚土层底面（基岩面）向上移动到接近结构的位置，通过缩减土-结构相互作用模型尺寸来提高计算效率。采用理论分析与数值算例，通过与采用整个深厚土层的传统土-结构相互作用分析结果对比，说明提出的高效分析方法能够满足精度要求，并且给出底面人工边界位置以及边界条件和地震动输入方式的建议。

EFFICIENT ANALYSIS SCHEME FOR SEISMIC SOIL-STRUCTURE INTERACTION WITH DEEP SOIL LAYER

The direct finite element method is a widely used time history method for seismic soil-structure interaction(SSI)analysis.In this method,the viscous-spring boundary condition is used to model the radiation damping of infinite domain,and the seismic site response is transformed into the equivalent loading.When the soil layer is extraordinary thick,the computational efficiency of seismic SSI analysis especially for three-dimensional problem is very low due to the finite element model of the whole deep soil layer.In this paper,an efficient analysis scheme is developed.In which,the one-dimensional site response analysis is still performed for the whole deep soil layer,and subsequently the bottom artificial boundary of SSI model is moved up from the actual soil layer bottom(bedrock surface)to the location sufficiently near the structure.The theoretical analyses and numerical examples are presented to indicate the accuracy and efficiency of the proposed efficient analysis scheme.The different boundary treatments and seismic inputs at different locations of the moved bottom boundary are compared with the finite element model of the whole deep soil layer.The proposed scheme meets the precision requirements,and some suggestions on artificial boundary treatment and location are given.