近场数值波动分析中地震波输入的一种简化方法

在显式有限元方法结合黏弹性人工边界的时域波动方法的基础上，建立了地震波垂直输入时的一种简化输入方法。将近场有限元模型沿高度方向进行分层，将地震动的入射运动转化为作用于人工边界底面及分层后每层侧面上的均布力，以实现地震动的输入。与以等效节点力的方式实现的地震动输入相比，施加均布力的方式简化了地震波输入的前处理工作，且又能保证与等效节点力方式相同的精度。自由场数值算例表明：当本文方法中的分层高度与波动有限元网格离散要求的最大尺寸相等时，本文方法与等效节点力方法具有相同的精度；当局部区域按网格离散要求的最大尺寸进行分层而在其它区域放大分层高度时，局部区域上的近场波动响应仍可保证具有相当高的精度。另外，某隧道结构地震响应算例的计算结果同样说明了本文方法的有效性。

A simplified seismic wave input method for near-field wave analysis

On the basis of the time-domain wave method coupled with the explicit finite element method for the viscous-spring artificial boundary issue, a simplified seismic wave input method for near-field wave analysis is proposed. In the present approach, the near-field model is stratified in the height direction, and then the seismic motion is converted to stress applied to the viscous-spring artificial boundary. Compared with the equivalent node force input method, the new method simplifies the antecedent work with acceptable accuracy. The numerical results obtained from free ground model indicate that: When the stratified size equals to the maximum size of the element mesh in dynamical analysis, the accuracy of the simplified model is totally same with that of the equivalent node method; when meshing the focus parts of the near-field model with the maximum size of dynamical analysis and meshing other parts with lager size, the dynamic response of caring part is still satisfied. Moreover, the dynamic response of a rock tunnel also demonstrates the effectiveness of the present simplified approach.