考虑多维地震动及重力作用的土层场地地震反应分析模型

Seismic response analysis model of soil-layer sites considering the combined effect of multidirectional seismic ground motions and gravity

合理有效的工程场地自由场分析是开展地下结构地震反应计算、发展地下结构实用抗震分析方法的前提。目前常用的自由场分析方法多局限于单向地震动输入,难以考虑多向地震动共同作用时的非线性耦合效应。鉴于此,提出一种考虑水平和竖向地震动及重力荷载共同作用的土层地震反应分析力学模型,该模型采用捆绑约束条件作为侧面边界条件,采用基于黏性边界的地震动输入方法将输入地震动转化为等效地震荷载,可实现自由场计算中水平和竖向地震动以及重力荷载的同时施加,简化了计算步骤,减少了计算成本。此外,该方法考虑了水平和竖向地震荷载的叠加效应,对于考虑材料非线性及大变形影响的土层场地地震反应分析具有更为良好的计算精度与适用性。

Reasonable and effective free-wave-field analysis of engineering sites is the premise of carrying out seismic response calculation and developing practical seismic analysis methods of underground structures.At present,the commonly used free-wave-field analysis methods are mostly limited to the case of unidirectional seismic wave input,and it is difficult to consider the nonlinear coupling effect when multidirectional ground motions are input together.In view of this,a unified free-wave-field analysis model for soil-layer site considering the combined effect of horizontal and vertical ground motions and gravity is proposed in this study.The binding constraints are adopted as the lateral boundary conditions in this model,and the seismic wave input method based on the viscous artificial boundaries is applied to convert the input ground motions into equivalent seismic loads,thereby the horizontal and vertical ground motions and gravity loads can be applied simultaneously in the free field analysis.By using this model,the calculation procedures can be simplified and the computational cost can be reduced.In addition,this model considers the combined effect of horizontal and vertical seismic loads,thus has better calculation accuracy and applicability for the seismic response analysis of soil-layer sites considering the influence of material nonlinearity and geometric nonlinearity.