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

本研究的目的是预测札幌地区近场地震引起的强烈地震动，并评估现有建筑物的结构损伤。假设札幌附近地震的断层参数是根据指定区域记录地震的震中分布和前人对地质构造的研究确定的。通过考虑凸起位置、断层破裂速度和断层角度等特定断层参数的变化，预测出一组地震动。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大楼。建筑模型考虑了屋顶上积雪的重量、应用建筑规范的产生和基础类型（固定或隔离）。确定了建筑物模型的参数，使模型能够反映实际建筑物的横向承载力和由振动观测得到的动力特性。预测的强地震动对建筑物的影响几乎与日本用于建筑物抗震设计的所谓2级地震动相同。裂缝的位置对结构损伤的影响最大。仅用峰值地加速度等单一参数对结构损伤进行评估是困难的。建筑物模型的横向承载力和动力特性也很容易改变预估损伤。建立了近场地震损伤的精确评估方法。

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.