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数值模拟是解决土-结构动力相互作用问题的重要手段,而合理地实现地震波动输入直接影响地震作用下土-结构动力相互作用问题数值模拟的精度。波动法是目前常用的地震动输入方法之一,该方法将输入地震动转化为人工边界上的等效荷载,相较于其他地震动输入方法,波动法模拟精度高,但实施上相对复杂。从有限元模型入手,推导了采用波动法确定等效输入地震荷载的另一种形式,以此为基础,提出了一种在人工边界上实现地震动输入的新方法。新方法通过对土-结构有限元模型中由包含人工边界节点的单元组成的子结构施加自由场位移时程并进行动力分析,直接获得可实现地震波动有效输入的等效荷载,然后将等效输入地震荷载施加在土-结构模型的人工边界节点上,从而完成土-结构动力相互作用问题分析中地震动输入和地震反应计算。与原有波动法相比,新方法避免了需分别计算人工边界上自由场应力和由引入人工边界条件带来的附加力,以及需要根据不同人工边界面确定荷载的作用方向等较为复杂的处理过程,具有等效地震荷载计算简便、地震动输入过程更易于实施的特点。采用竖直入射和斜入射地震波动作用下的弹性半空间和成层半空间地震反应算例验证了新方法的有效性。
Numerical simulation is an important method to solve the soil-structure dynamic interaction problem. However, the reasonable realization of seismic wave input directly affects the precision of numerical simulation of soil-structure dynamic interaction under earthquake action. Fluctuation method is one of the commonly used methods for inputting ground motion. The method converts the input ground motion into the equivalent load on the artificial boundary. Compared with other ground motion input methods, the wave method has a high accuracy of simulation, but it is relatively complicated to implement. Based on the finite element model, a new method to determine the equivalent input seismic load using wave method is deduced. Based on this, a new method to realize the seismic input on the artificial boundary is proposed. In the new method, the free-field displacement time-history of the substructure composed of elements with artificial boundary nodes in the soil-structure finite element model is analyzed and the dynamic analysis is performed to directly obtain the equivalent load that can effectively input the seismic wave. Then, The input seismic loads are applied to the artificial boundary nodes of the soil-structure model to complete the input of seismic motion and the seismic response calculation in the analysis of the soil-structure dynamic interaction problems. Compared with the original wave method, the new method avoids the need to separately calculate the free field stress on the artificial boundary and the additional force caused by the introduction of the artificial boundary conditions, and the complicated process of determining the action direction of the load according to different artificial boundary surfaces , Which has the characteristics of simple calculation of equivalent seismic load and easier implementation of ground motion input. The effectiveness of the new method is validated by the seismic half-space and half-space seismic responses under vertically and obliquely incident seismic waves.