摘要:以某多层框架结构为工程背景，通过PLAXIS 3D有限元程序构建包含上部结构与地基基础的三维数值模型，借助程序内嵌的弹塑性分析功能；首先，采用SAP2000建立结构有限元模型，在PLAXIS 3D中采用与其相同的底部约束条件，对比仅考虑自重作用时两模型中结构内力的差异，验证PLAXIS 3D进行框架结构内力分析的计算精度；然后，分别考虑小震与大震两种工况，采用拟静力方法，对结构施加水平地震力，研究土-结构共同作用下结构内力与不考虑共同作用时结构内力的差异性；最后，除PLAXIS3D整体模型之外，考虑将上部结构简化为均布荷载，分析两种情况下基础沉降的差异性。结果表明，建立土体与结构的整体三维模型可以直接考虑地基基础与上部结构的刚度协调，从而获得更加符合实际的结构内力和基础变形。

Abstract: In the engineering background of a multistory frame structure, a PLAXIS 3D numerical model including superstructure, foundation and subsoil is built for elasto-plastic analysis. Firstly, in the PLAXIS 3D model, the same constraint condition is applied using SAP2000 to build the structural finite element model. The structural internal force in consideration of only gravity function from the two models is compared for verifying the calculation accuracy of PLAXIS 3D structure model. Secondly, the differences of structural internal force obtained by considering interaction or not are studied in two cases of small earthquake and large earthquake with pseudo-static analysis. Finally, the differences of foundation settlement between the full 3D model and the simplified model, in which superstructure is replaced by uniform distributed load, are analyzed. The numerical results indicate that full 3D model of superstructure, foundation and subsoil considers stiffness coordination directly and gives structural internal force and foundation settlement conforms to reality better than the simplified structure model.