Development of a frequency- and amplitute-dependent macro element for seismic SSI analysis of shallow and deep foundations

建议的研究的目的是开发一个计算效率高的数值单元，可以捕获的非弹性和频率依赖性的浅，深基础的地震土-结构相互作用分析。明确建模的土壤基础系统的挑战之一是系统的动态负载下的响应的复杂性。在现实中，地基系统是一个大型的半无限连续体与非弹性材料。在土壤和基础之间的界面处的非线性（即摇摆和滑动）也影响基础的滞后行为。此外，土-基础系统的动力响应是频率相关的。根据土壤基础和结构系统的相对阻抗，非弹性和频率相关特性都需要在数值模型中表示。然而，在简化的模型中，例如集总或Winkler弹簧模型，很难捕捉这些特性。在拟议的研究中，广义宏单元将开发与近场土壤的非弹性行为和频率依赖特性的土壤-基础系统可以模拟。PI和行业合作伙伴开发了一个框架，其中宏元素可以与递归参数模型集成。宏单元是基于塑性理论，捕捉近场土壤的非弹性，而递归参数模型捕捉频率相关的特性。该框架被应用到一个二维浅基础。在这项拟议的研究中，该框架将被推广，使其可以适用于两个二维和三维问题的浅和深的基础。该单元将根据现有的实验测试结果和复杂的有限元分析进行校准和验证。该单元将减少建模工作量和计算时间，同时为结构的地震评估提供实际精确的土-地基系统响应。该元件的开发将导致安全和优化的建筑物和桥梁结构。

The objective of the proposed research is to develop a computationally efficient numerical element which can capture both the inelasticity and the frequency dependency of shallow and deep foundations for seismic soil-structure-interaction analyses. One of the challenges in explicitly modelling a soil-foundation system is the complexity of the system's response under dynamic load. In reality a soil-foundation system is a large semi-infinite continuum with inelastic material. The nonlinearity at the interface between the soil and the foundation (i.e. rocking and sliding) also influences the hysteretic behaviour of the foundation. In addition, the dynamic response of the soil-foundation system is frequency dependent. Depending on the relative impedance of the soil-foundation and the structural system, both the inelasticity and the frequency dependent characteristics need to be represented in a numerical model. In a simplified models, such as lumped or Winkler spring models, however, it is difficult to capture these characteristics. In the proposed research, a generalized macro element will be developed with which the inelastic behavior of near-field soil and the frequency dependent characteristics of the soil-foundation system can be modelled. The PI and the industry partner has developed a framework in which a macro element can be integrated with a recursive parameter model. The macro element is based on a plasticity theory and captures the inelasticity of near field soil while the recursive parameter model captures the frequency dependent characteristics. The framework was applied to a two-dimensional shallow foundation. In this proposed research, the framework will be generalized such that it can be applied to both shallow and deep foundation for both two- and three-dimensional problems. The element will be calibrated and validated against available experimental test results and sophisticated finite element analyses. The element will reduce the modelling efforts and computational time while providing practically accurate response of soil-foundation system for seismic assessment of structures. The development of the element will lead to safe and optimized buildings and bridge structures.