Seismic performance of underground structures based on realistic soil and structural model

本研究旨在了解地下结构地震土-结构相互作用（SSI）分析常用数值模拟方法的准确性和局限性。为了准确地模拟地震SSI效应对地下结构的影响，有必要用真实的数值单元模拟土壤和结构。特别是当地下结构出现裂缝或局部破坏时，现有的基于理想弹性体系的数值评估方法不能保证准确性。在当前的设计和性能评估实践中，地下结构的地震SSI是通过使用一个非常简化的方法来计算的，该方法基于线弹性土-结构系统的广泛假设。本研究的目的是基于真实的土壤和结构模型来研究地下结构的抗震性能。其主要目的是：1）通过与具有土壤和结构精确表示的数值模型进行比较，评估传统评估方法的准确性; 2）评估附近结构对地下结构地震需求的影响。研究的范围是 仅限于受到地面震动的理想化地铁站。数值模型将建立在一个分布式模拟框架上，该框架允许将不同的分析模型集成在一个模拟中。利用这一先进的建模技术，将调查影响结构抗震性能的各种因素。数值结果将与封闭形式的解决方案进行比较，以进一步解决在实践中使用的简化方法的局限性。

The research aims to understand the accuracy and limitations of commonly used numerical modelling methods for seismic soil-structure-interaction (SSI) analysis of underground structures. To accurately simulate the seismic SSI effect on underground structures, it is necessary to model both soil and structures with realistic numerical elements. Especially, if cracks or local failure develops in the underground structure, the current numerical assessment method based on idealized elastic system is not expected to be accurate. In current design and performance assessment practice, the seismic SSI of underground structure is accounted for by using a very simplified approach which is based on sweeping assumptions on linear-elastic soil-structure system. The proposed research aims to investigate the seismic performance of underground structures based on realistic soil and structural model. The main goal is 1) to evaluate the accuracy of the traditional assessment methods in comparison with a numerical model with accurate representation of soil and structure, and 2) to evaluate the influence of nearby structure on the seismic demand on underground structure. The scope of the study is limited to an idealized subway station subjected to ground shaking. The numerical model will be built upon a distributed simulation framework which allows different analytical models to be integrated within one simulation. Taking the advantage of this advanced modelling technique, various factors influencing the seismic performance of the structure will be investigated. Numerical results will be compared with the closed form solutions to further address the limitations of the simplified methods that are being used in practice.