地基动力阻抗的双自由度集总参数模型

在土－结构动力相互作用分析中，下覆地基对基础与结构的阻抗函数通常强烈地依赖于外加激振频率。当结构为线性时，耦联体系的动力分析可采用子结构法在频域上有效地实施。但对于非线性结构，在时域上要用与频率有关的动力阻抗进行相互作用分析就变得十分困难与复杂。而单靠采用某一频率下动力阻抗函数固定值的单自由度集总参数模型不能充分地包含所有频率成分而难以反映实际性态。

2 DOF lumped parameter model of dynamic impedances of foundation soils

In the dynamic soil structure interaction analysis, the dynamic impedances of foundation soils on the super structure and footing are of frequency dependent nature. Frequency domain formulations for solving seismic response of coupling systems have gained popular usages for linear elastic problems. For nonlinear systems in common practice, it is difficult to perform soil structure interaction analysis in time domain while the frequency dependent impedances are directly employed. The conventional simple lumped parameter model with constant spring and damping coefficients cannot simulate the actual behaviour of foundation and soil system. In order to overcome these deficiencies and drawbacks, a two degrees of freedom mechanical model with 8 constant lumped parameters is developed for the foundation dynamic impedances on the basis of accurate values of soil impedances evaluated by numerically solving actual boundary value problems. This discrete model is simple and applicable in practice. It provides a useful basis for the nonlinear analysis of soil structure interaction system in the time domain.