Seismic performance evaluations of the existing buildings based on the prediction of the strong ground motions caused by near-field scenario earthquakes

研究的目的是预测近场地震引起的强地面运动，并评估札幌地区既有建筑的结构破坏。根据所记录地震在特定地区的震中分布和前人对地质构造的研究，确定了表征假想札幌近震的断层参数。通过考虑指定的断层参数(如凹凸体的位置、断层破裂速度和断层角度)的变化来预测一组地面运动。利用预测的强地震动进行了一系列地震反应分析。建造了四种类型的建筑模型，分别是一座木屋、两座钢筋混凝土建筑和作为历史重要建筑的前北海道政府办公楼。建筑模型考虑了屋顶积雪的重量、适用建筑规范的生成和基础类型(固定或隔离)。确定了建筑模型的参数，以使模型能够反映实际建筑的预期水平承载力和通过振动观测获得的动力特性。预测的强地震动对建筑物的影响与日本建筑抗震设计中所采用的所谓二级地震动的影响几乎相同。凹凸体的位置对结构损伤的影响最大。仅用地面峰值加速度等一种参数很难对结构的损伤进行评估。估计的损失也很容易随建筑模型的横向承载能力和动力特性而改变。建立了精确评估近场地震震害的程序。

The purpose of the research is to predict the strong ground motions caused by near-field earthquakes and to evaluate the structural damages of the existing buildings in Sapporo region. The fault parameters characterizing the hypothetical close-by Sapporo earthquakes were determined from the epicenter distribution of the recorded earthquakes in the specified region and the previous researches about the geological structure. A set of ground motions were predicted by considering the variance of the specified fault parameters such as the location of asperity, fault rapture velocity and fault angle. A series of seismic response analyses were conducted using the predicted strong ground motions. Four types of building models were constructed, which were a wooden house, two of reinforced-concrete buildings and the Former Hokkaido Government Office Building as a historically important building. The weight of snow on the roof, generation of the applied building codes and foundation types (fixed or isolated) were considered for the building models. The parameters for the building models were determined so that the models can represent the lateral capacity expected as a real building and the dynamic properties obtained from the vibration observation. The influence to the buildings of the predicted strong ground motions were almost the same as the so-called Level-2 ground motions which have been used for the seismic design of the buildings in Japan. The location of the asperity provided the largest influence to the structural damages. It was difficult to evaluate the structural damage using only one type of parameter such as the peak ground acceleration. The estimated damages were also easily changeable by the lateral capacity and the dynamic properties of the building models. The procedure of the precise evaluation of the damages caused by near-field earthquake was established in the research.