Joint Study on Urban Seismic Disaster of Irregular Site

在不规则场地城市震害联合研究中，研究了不规则地形场地对地面运动特性和城市地震灾害的影响。研究的第一部分是在同济大学中国和日本丰桥工业大学进行的地震运动观测。分析结果表明，无论输入的地震运动是什么，如震中、入射方向、震级等，不同地震的频谱比对各个观测点的变化趋势是一致的。为了比较观测结果和理论结果的放大效果，根据实际地面条件，分别采用一维和二维模型进行了分析。结果表明，入射波的方向和角度对放大的影响不大，而地形条件对放大的影响较大。基于…的轴对称沟谷响应分析对于入射波，我们发现：a)相应的放大在谷心最大，向边缘减小；b)基频仅取决于谷心的一维频率和形状比，而与入射波场和阻抗对比度无关。所提出的经验公式可以准确地估计基波频率。c)谷心的基波共振幅度取决于形状比和阻抗对比度。所提出的经验公式可以近似估计基频共振振幅。第二部分考虑了城市地区(上海和东京)的地震危险性估计。利用概率方法，分析了地震时道路和街道的失灵主要受房屋和建筑物的倒塌和火灾破坏的影响。地震疏散风险评价结果表明，居民疏散风险受人口密度、道路和街道故障、避难岛数量等因素的影响。并通过对历次历史地震、地基条件和民居建筑结构特征的研究，发现上海的地震危险性低于东京。较少

In the joint study on urban seismic disaster of irregular site, the effects of irregular topography site in behavior of ground motions and urban seismic disasters are investigated. The first part of the study the seismic motion observation in China (Tongji University) and Japan(Toyohashi University of Technology) were carried out. From the analysis the results showed the spectral ratios of different earthquake indicate the same tendency for individual observation point regardless of the input earthquake motion, such as the epicenter, incident direction and the magnitude. In order to compare the amplification effects of the observational results and theoretical results, the analysis based on the actual ground conditions has been performed by using 1-dimensional and 2-dimensional model. It was found that the amplification was not influenced very much by the direction and angle of incident wave but by the topographical conditions. From the response analyses of axisymmetric valleys subject … More ed to incident waves, it found thata) The corresponding amplification is maximum at the valley center and decreases toward the edges.b) The fundamental resonance frequencies depend only on two parameters, namely, the onedimensional frequency at the valley center and the shape ratio, regardless of the incident wave field and the impedance contrast. The proposed empirical formulas can estimate accurately the fundamental frequencies.c) The fundamental resonance amplitudes at the valley center depend on the shape ratio and the impedance contrast. The proposed empirical formulas can estimate approximately the fundamental resonance amplitudes.In the second part the estimation of earthquake risk in urban areas (Shanghai and Tokyo) are considered. By the using the probabilistic method, the malfunction of the roads and streets during earthquake were influenced by the collapse of houses and building and the destruction of them by fire. From earthquake evacuation risk evaluation, the results showed that the evacuation risks of inhabitants were influenced by population density, the malfunction of the roads and streets and number of refuge islands. And in the study the past histrical earthquakes, subsoil conditions and structural characteristics of residential houses and building , it was found that the earthquake risk in Shanghai were lower than in Tokyo. Less