Estimation of Ultimate Safety for Soil-structure Interaction System and its Application to Aseismic Design

在本项目中，我们提出了几种分析和实验方法和理论，以发展土-结构相互作用体系的弹性和延性设计方法相结合的抗震设计。本文主要研究了以下四个方面的问题：(1)土-结构动力相互作用的评价，开发了基于子结构法和有限元法分析基础结构体系的计算机程序。考虑土与结构之间的滑动、分离以及材料的非线性，分析了三维土-结构相互作用系统的动力非线性行为。(2)基础结构破坏过程分析采用实验和分析相结合的方法，对颗粒结构和基础结构的动力稳定性进行了研究。本文提出了一种新的实验技术，用于在模型中可视化粒子互锁的动力学行为。用离散元法（DEM）验证了该方法的有效性。将DEM应用于桩承载力动力问题的研究。(3)地下结构和基础结构的试验研究通过试验和数值模拟研究了水平作用于地下管道侧壁上的非线性动土压力。对桩基础的非线性恢复力特性进行了测量和识别。本文提出了一种简单的分析方法来模拟桩-土体系的行为。(4)土-结构体系简化模型的建立为了简化土木结构的抗震设计，将土-结构相互作用的耦合体系替换为简单的摇摇（S-R）模型。提出了利用微震谱比估计地基振动特性的简单方法。

We have proposed several analytical and experimental methods and theories in this project to develop earthquake resistant design which combines the elastic and ductile design methods of soil-structure interaction system. The following four topics has been investigated :(1) Evaluation of dynamic soil-structure interactionA computer program has been developed to analyze foundation structure systems by substructure method and FEM. We analyzed dynamic nonlinear behaviour of three dimensional soil-structure interaction system taking into account sliding and separation between soil and and structures as well as material nonlinearity.(2) Analysis of failure process of foundation structuresDynamic stability of granular structures and foundation structures were studied by use of experimental and analytical methods. A new experimental technique to visualize dynamic behaviour of particles interlocking in a model was developed. The efficiency of this technique was examined by Distinct Element Method (DEM). DEM was applied to the dynamic problem of bearing capacity of piles.(3) Experimental study of underground structures and foundation structuresNonlinear dynamic earth pressure acting horizontally on side walls of an underground conduit was investigated by the experiments and numerical simulation. A hybrid study has been done to measure and identify nonlinear restoring force characteristics of pile foundations. A simple analytical method to simulate the behavior of soil-pile systems has been developed.(4) Development of simplified model for soil-structure systemFor the purpose of a simple aseismic design of civil structure, the coupling system of soil-structure interaction was replaced to the simple sway-rocking (S-R) model. Simple estimation method of the vibration characteristics for the ground was developed by use of the spectrum ratio of microtremors.