Soil-structure-interaction (SSI) analyses are essential to evaluate the seismic performance of important structures before finalizing their structural design. SSI under seismic condition involves much more complex interaction with soil compared to the dynamic loads having source on the structure. Seismic SSI analysis requires due consideration of sitespecific and structure-specific properties to estimate the actual ground motion (scattered motion) experienced at the base of the structure, and subsequently the effects of the scattered motion on the structure. Most challenging aspect of seismic SSI analysis is to implement transmitting boundaries that absorb the artificial reflections of stress waves at the truncated interface of the finite and infinite domains, while allowing the seismic waves to enter the finite domain. In this paper, the time domain implementation of seismic analysis of a soil-structure system is presented using classical discrete models of structure and interactive force boundary conditions for soil. These models represent typical SSI systemsa single Degree of Freedom (DOF) of a spherical cavity with mass attached to its wall, a two DOF system consisting of a mass attached by a nonlinear spring to a semi-infinite rod on elastic foundation, and a three DOF system with additional DOFs for modelling the structural stiffness and damping. The convolution integral representing the force boundary condition on the truncated interface, is evaluated interactively using UAMP user-subroutine in ABAQUS and applied as concentrated forces at the interface (truncated interface) nodes of the bounded domain or generalized-structure domain. The verification problems presented in the paper show the satisfactory performance of the developed MATLAB code and ABAQUS implementation with FORTRAN user-subroutines. The classical phenomena associated with the dynamic soil-structure systems are discussed through the present work. KeywordsSoil-structure interaction, Seismic analysis, Transmitting boundaries, ABAQUS, UAMP subroutine.

中文翻译：

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离散土壤-结构相互作用系统中ABAQUS传输边界的时域实现

在完成重要结构的结构设计之前，土壤-结构相互作用（SSI）分析对于评估重要结构的抗震性能至关重要。与在结构上具有源的动态载荷相比，地震条件下的SSI与土壤的相互作用要复杂得多。地震SSI分析需要适当考虑特定地点和特定结构的属性，以估计在结构底部经历的实际地面运动（散射运动），然后评估散射运动对结构的影响。地震SSI分析中最具挑战性的方面是实现传输边界，该边界吸收应力波在有限域和无限域的截断面处的人工反射，同时允许地震波进入有限域。在本文中，利用经典的离散结构模型和相互作用力边界条件，提出了土-结构系统地震分析的时域实现方法。这些模型代表了典型的SSI系统：球形腔的单自由度（DOF），其壁上附着有质量；两个DOF系统，其质量由非线性弹簧附着到弹性基础上的半无限杆上；三个具有附加DOF的DOF系统，用于对结构刚度和阻尼进行建模。使用ABAQUS中的UAMP用户子例程交互地评估代表截断界面上力边界条件的卷积积分，并将其作为集中力应用于有界域或广义结构域的界面（截断界面）节点。本文中提出的验证问题表明，使用FORTRAN用户子程序开发的MATLAB代码和ABAQUS实现的性能令人满意。通过目前的工作讨论了与动态土壤结构系统有关的经典现象。关键词：土-结构相互作用，地震分析，传输边界，ABAQUS，UAMP子程序。