地震作用下土‐深埋地下结构相互作用的高效时程分析方法?

基于黏弹性边界和将场地地震反应转化为等效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。当结构埋深较深时,整个土-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。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-结构计算模型的自由表面向下移动、底边界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,并且针对不同结构尺寸、结构埋深和围岩等级给出上、下人工边界位置的建议。

Efficient Analysis for Seismic Soil-structure Interaction with Deep Burial Depth

The direct finite element method has been widely used in the soil-structure interaction(SSI) analysis.It is achieved by transforming the site response into the equivalent loading based on the viscous-spring boundary condition.When the structure is deeply buried in the soil,the whole finite element model of the SSI system contains too many degrees of freedom,especially for the three-dimensional problem,so that the computation efficiency is low.In this paper,an efficient analysis scheme is developed.In this new scheme,the one-dimensional site response analysis is still performed for the whole deep soil layer.Subsequently,the artificial bottom and top boundaries of the SSI model are moved up from the bottom of the actual soil layer(bedrock surface) and down from free surface,respectively,to the locations sufficiently near the structure.The theoretical analysis and numerical examples indicate that the proposed efficient analysis scheme satisfies the requirements of precision,even when the location of the artificial boundary is sufficiently near the structure.The boundary location is discussed based on some parametric analyses regarding the structure size,its buried depth and the surrounding rock grade.