外源波动问题数值模拟的一种实现方式

将人工边界上的波动场分解为无局部场地效应影响的自由场与局部场地效应引起的散射场两部分,无限域地基中的波动传播对人工边界的影响通过将位移场、速度场转化为应力场施加到人工边界节点上来反映,其中散射波场的模拟采用了杜修力等提出的一种远场近似解。在此基础上,利用通用有限元软件实现了斜入射条件下瞬态平面地震波作用引起的局部场地效应的时域数值模拟,为计算二维、三维局部不规则、非均匀场地的地震局部场地效应以及土结动力相互作用等外源波动问题提供了一种有效、实用的实现方式。建议方法的优点是可直接借助通用有限元软件强大的求解器和前后处理功能来计算和分析近场波动反应,且实现简便。实际上,由于通用有限元软件强大的求解功能,可方便地用于局部场地存在不均匀、非线性的情况。

AN APPROACH TO NUMERICAL SIMULATION FOR EXTERNAL SOURCE WAVE MOTION

The wave field of artificial boundary is separated into free field without local topography effect and scattering field induced by local topography effect. In infinite ground, the influence of wave propagation on artificial boundary is realized by transforming displacement field as well as velocity field to stress field which are imposed on the boundary nodes, and scattering wave field is modeled as a far field approximately solution introduced by Du Xiuli. On this basis, the time domain numerical simulation of local topography effect under obliquely incident transient plane wave can be performed in virtue of general FEM software. Thusly, an efficient method to calculate external source wave motion such as local topography effect in two or three dimension irregular, uneven field and soil structure dynamic interaction is developed. The advantage of the proposed method will simplify the analysis of nearfield wave with strong solver and pre-post process of general finite element software. In fact, due to the strong calculation function of general FEM software, the method can easily applied to the analysis of uneven and nonlinear problems.