层状地基-非线性结构系统地震响应特性分析

Analysis of seismic response properties of layered foundation-nonlinear structure system

根据从系统能量导出的地震动力方程,采用渐近解析法对层状地基-非线性结构系统的地震响应进行了分析,给出了共振区的振幅-频率以及相位-频率的解析公式,并对地基参数的不同取值,给出了一系列相应的计算结果。进而根据计算结果分析了地基参数对结构地震响应特性的影响,讨论了共振区畸变、振幅的分叉和突变现象以及“路径”效应等非线性动力特性。分析结果表明,同一类别地基的参数变化对结构的动力特性有显著的影响,按现行抗震设计方法对层状地基-非结构系统进行抗震分析时,可能产生较大的偏差,需考虑相互作用和非线性特性,以使设计参数更合理和优化。

On the basis of dynamic equations for seismic analysis derived from system energy, the seismic response of layered foundation-nonlinear structure system is studied by means of asymptotic method (KBM). The analytical formulas of amplitude-frequency and phase-frequency are obtained. A series of calculating results for different values of foundation parameters are presented in seismic resonant area. And then according to corresponding calculating results, the effect of foundation parameters on seismic properties of structure is analyzed; and the nonlinear dynamic characteristics,such as distortion of resonant area, bifurcation and suddenly jumping of amplitude, as well as the path effect , are discussed. It is indicated that the value change of foundation parameters of the same sort causes remarkable influence on structure dynamic properties, and the calculating error by the current Code of seismic design might be obvious for the analysis of layered foundation- nonlinear structure system. The interaction between soil and structure and nonlinear properties must be considered in order that design parameters are more reasonable and optimal.