Studies on Seismic Safety of Structure-Soil Interaction System and Its Rational Design Procedures

本研究旨在通过对扩展大型土木工程结构的动力相互作用分析，为此类结构的设计提供有用的信息。(1)具有局部地形的土层中波的传播；(2)土-结构动力相互作用及地基阻抗和有效输入运动；(3)强震作用下土体的非线性效应对结构响应的影响；(4)多输入结构的递进输入运动。采用了频域分析、时间域分析以及两者相结合的方法。所使用的参数包括入射波型、入射角、地形、土层宽深比。对由表面宽度…定义的代表性无量纲频率进行分析更多的是沉淀物和入射波长。局部地形引起的土体放大效应与波型和无因次频率有很大关系，对于集中力和均匀分布力，建立了边界元分析中涉及的格林函数。傅里叶变换方法需要对波数进行积分才能进行逆变换。这是通过高斯求积和改进的Clenshaw-Curtis方法来实现的。多层格林函数的引入，使层状半空间土体的分析成为可能。对间接边界元方法中的源力偏移问题进行了详细的讨论。采用Cgniad-de Hoop法求全平面的解析解，在软土地基上建造群桩基础来支撑上部结构。本文的分析考虑了桩-土-桩的相互作用。采用了子结构法，将土体和桩分开。土体分析采用薄层方法。桩的分析分为质量离散系统和质量分布系统。研究的重点是桩头阻抗函数。模拟了单桩荷载试验，研究了刚性埋置基础的土层分层、相邻地基通过土体的相互作用、回填效应。在强地震动作用下，土体表现出高应变，表现出强烈的非线性行为，非周期地震输入的基线漂移。在假定应力应变关系一定的情况下，采用直接逐步积分法和基于有效应变的等效方法对一维和二维模型进行了响应计算。对计算结果进行了时程分析和反应谱比较。阐明了建模的区别和非线性的特点。为了解释记录数据，强调了二维建模的重要性。研究了考虑土的非线性特性的桩基结构响应，并进行了当量线性分析。土体变形是基于假定的土体应力应变特性。虽然等效线性化技术合理地预测了真正的非线性响应，但随着输入运动的增加，这些响应之间的差异变得明显。特别是，这种非线性结构反应导致加速度减小，但位移放大。较少

This study aims at getting useful information for design of extended large scale civil engineering structures through the analysis of such structures with emphasis on dynamic soil structure interaction. The following issues has been focused :(1) Wave propagation in the soil deposit with the local topography(2) Dynamic soil-structure interaction and the foundation impedance and the effective input motion(3) Nonlinear soil effect in strong earthquake motion on structural response(4) Progressive input motion to multiple input structuresTopographical study of the construction site is made to investigate the seismic wave amplification in 2 dimensional sense. The frequency domain analysis, the time domain analysis and their hybrid approach have been employed. The parameter used are the incident wave types, angle of incidence, topography, aspect ratio between wide and depth of the soil deposits. Analysis is conducted for representative nondimensional frequency as defined by the surface width … More of the deposit and the incident wave length. Soil amplification due to the local topography depends significantly on the wave type and noodimension frequency.The Green function involved for the BEM analysis is developed for the concentrated as well as uniform distributed forces. The Fourier transform method needs the wave number integration for the inverse transform. This is performed by the Gauss quadrature and by the modified Clenshaw-Curtis method. The Green function for multilayer makes it possible to perform the soil deposits with layered half space. Detail discussion is made for the offset of source forces in the indirect boundary element method. The time domain analysis used the Cgniad-de Hoop method for the analytical solution for a full plane.Group pile foundations are constructed on soft soils to support superstructures. The present analysis took deliberate consideration for the pile-soil-pile interaction. The substructure method is used to advantage, splitting the soil and piles. The soil analysis is performed by use of the thin layer method. The pile analysis is made from the mass discrete system and the mass distributed system. The investigation is focused the pile head impedance function. The simulation is carried out for a single pile loading test.The investigation for rigid buried foundations is also executed with interest to soil layering, the interaction between adjacent foundation through soil, fillback effect.Soils in strong ground motion attain high strains, indicating heavily nonlinear behavior with drift of the base line for the nonperiodic seismic input. Assuming certain stress-strain relationship, response computation are made for the 1-dimensional and the 2-dimensional models by the direct step-by-step integration scheme and by the equivalent method based on effective stain. The results are compared for the time histories and the response spectra. The difference of modeling and the characteristic of nonlinearity are clarified. The importance of the 2-dimensional modeling is emphasized in order to interpret the recorded data.Pile supported structural response with nonlinear soil properties is investigated, together with the equivalent linear analysis. Soil-deformation is based on the assumed soil stress-strain characteristic. Although the equivalent linearization technique predicts reasonably the truly nonlinear response, the difference between these responses becomes appreciable as the input motion grows. Especially, such nonlinear structural response gives rise to reduced acceleration but amplified displacement. Less