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土层动力反应分忻是进行地震小区划和选择重点工程设计地震动的重要手段之一。Iwan模型能较好地反映循环荷载下土的应力应变关系。本文着重讨论了Iwan模型中附加阻尼元件的特性。作者指出,该元件实际上等效于在运动方程中附加一个阻尼项;它和模型的连接方式,即取串联或并联的连接方式,决定于模型的荷载是力还是变位。据此编制了一个用显式差分方法分析一维场址动力反应的计算程序,该程序考虑了边界能量的透射和孔隙水压力的产生对士层反应的影响。文中还简略介绍了运用Iwan模型于烟台市地震小区划的结果。
Soil dynamic response is one of the important means to carry out earthquake subduction and select key engineering design ground motions. The Iwan model can better reflect the stress-strain relationship of the soil under cyclic loading. This article focuses on the characteristics of the additional damping elements in the Iwan model. The author points out that this element is actually equivalent to adding a damping term to the equation of motion; it is connected to the model by taking series or parallel connections depending on whether the model’s load is a force or a displacement. Based on this, a computational program for analyzing the dynamic response of one-dimensional site using the explicit difference method was developed. This program considers the influence of the transmission of boundary energy and the generation of pore water pressure on the strata response. The paper also briefly introduced the results of the earthquake subdivision using the Iwan model in Yantai City.