MITIGATION OF DAMAGE TO FOUNDATIONS CAUSED BY EARTHQUAKES

本文总结了近三年来的研究成果，主要有：在研究刚性基础的地震破坏时，了解基础的动力特性是非常重要的。因此，动态弹簧常数和阻尼系数进行了初步研究，刚体基础的直接和外部振动试验。同时，考虑到不同方向的地震动输入，刚性基础同时承受扭转振动和竖向振动。在进行这些试验之后，作为本研究的主要部分，进行了关于减轻地震对地基损害的试验。本报告详细介绍了采用基础隔震设计的基础的振动试验。在矩形刚性基础附近安装圆形基础隔震结构（直径0.2 m），作用在基础上的地震运动衰减为伊娃 ...更多信息 luated。在安装基础隔震结构之前，测量了基础对地震运动的反应。地震地面运动是通过在距离地基中心6 m处埋设一个垂直墙，并在一个类似于地震的运动中对墙撞击一个1.0 t的混凝土块来产生的。通过改变块体的摆动高度来改变地震动的强度。通过测量距离地面运动源1.0m处的加速度并计算所测加速度与地基响应的比值，对地基的响应进行了评估。通过对单线和双线基础隔震结构的试验研究，评价了基础隔震结构的减震效果，结果表明，在地震动较小的情况下，无基础隔震结构的地震反应小于有基础隔震结构的地震反应。然而，基础隔震的阻尼效果随着地震动的增加而变得显著。结果表明，采用一排隔震结构和两排隔震结构的计算结果无显著性差异，表明一排隔震结构足以产生减震效果。少

The studies carried out in the latest three years are summarized as follows.When studying the mitigation of damage to rigid-body foundations by earthquakes, it is very important to know the dynamic properties of the foundations. Thus, dynamic spring constants and damping coefficients were preliminarily investigated by subjecting rigid-body foundations to direct and external vibration tests. Also, in consideration of earthquake motion inputs from different directions, rigid-body foundations were subjected to torsional and vertical vibrations simultaneously. After carrying out these tests, experiments concerning the mitigation of damage to foundations by earthquakes were conducted as the main part of this study. Vibration tests of foundations incorporating base-isolation designs are detailed in this report.Circular base-isolation structures (0.2-m diameter) were installed near a rectangular rigid-body foundation, and the reduction of the earthquake motion acting on the foundation was eva … More luated. Before installing the base-isolation structures, the response of the foundation to earthquake motion was measured. Earthquake ground motion was generated by burying a vertical wall at a distance of 6 m from the foundation center and impacting a 1.0-t concrete block against the wall in a pendulum-like motion. The intensity of the ground motion was varied by changing the swinging height of the block. The response of the foundation was evaluated by measuring acceleration at a point 1.0m from the ground motion source and calculating the ratio of the measured acceleration to the foundation response. Tests were carried out with both one line and two lines of base-isolation structures and their effect of ground motion damping was evaluated.The results indicate that, when ground motion is small, the foundation without base isolation exhibits smaller response than the foundation with base isolation. However, the damping effect of base isolation becomes significant with increasing ground motion. No significant difference is found between the results obtained by the one-line and the two-line base isolation structures ; this indicates one line of base-isolation structures is sufficient to bring about the effect of ground motion damping. Less