应用通用程序计算深覆盖土层地震反应的几个问题

摘要

Several problems in seismic response analysis of soil layer with deep deposit were discussed using ANSYS and LS-DYNA.The effects of some factors,such as,selection of calculation scope of soil layer,division of mesh elements,formation of damping matrix,etc.calculation accuracy were analyzed by comparing the numerical results obtained with the general programs.Numerical examples demonstrated that the relationship between the fundamental frequency of soil layer and the predominant frequency of earthquake excitation is an important factor to affect calculation accuracy;when the former is smaller than the latter,especially,much smaller than the latter,the proportional coefficients in damping matrix should be formed with the two frequencies;the vertical and horizontal grid sizes and the selection of artificial boundary have a significant influence on calculation results.%讨论了利用ANSYS和LS－DYNA程序进行深覆盖土层地震反应时域计算时所涉及的几个问题。综合前期研究成果，通过对比通用程序的数值计算结果，分析了数值计算时土层计算范围的选取及单元网格划分、阻尼矩阵的形成等对计算精度的影响。分析结果表明：在确定深覆盖土层阻尼矩阵的比例系数时，土层基频与地震激励主要特征频率之间的关系是一个重要影响因素，当前者小于后者，特别是远小于后者时，应基于土层的基频与地震激励的主要特征频率来形成阻尼矩阵的比例系数；竖向、横向网格尺寸及人工边界的选取会对计算的结果造成显著影响。