Susumu Minami

RECONNAISSANCE OF DAMAGED STEEL SCHOOL BUILDINGS DUE TO THE 2011 TOHOKU EARTHQUAKE

An outline of a reconnaissance of steel school buildings damaged by the 2011 Tohoku earthquake is presented. In this reconnaissance, a total of 216 facilities have been investigated by the Steel Structure Working Group of the Subcommittee on Seismic Performance of School Buildings, Architectural Institute of Japan. The damage to structural elements, connections, non-structural elements, foundation and surrounding soil, as well as the details including building history and seismic retrofit have been recorded and the overall damage has been evaluated based on the “Standard for Post-earthquake Damage Evaluation of Damaged Buildings” published by the Japan Building Disaster Prevention Association. Not only seismic damage but damage caused by the devastating tsunami are also covered. Detailed analysis of the damage to individual structural and non-structural components are presented in following papers.

Study on fracture condition of biaxially loaded connections in steel structure.

It is considered that the fracture of beam-to-column connections in steel structures occurs after the slow crack growth, when structures are subjected to repetitive large strains such as a strong earthquake exciation.The purpose of the present experiments and analysis was to investigate the influences of fracture toughness, temperature and stress distribution on their fracture conditions. This paper deals with the investigation on fracture of subassemblages including beam-to-column connections with notch and lamination under biaxial force. The axial stress ratio (axial stress of column/yield stress) was varied. The model was analyzed by using the elasto-plastic finite element method. The results of the analysis and the experiments are as follows.J-integral of these analytical models was influenced by the axial stress which is parallel to the crack; the higher the compressive axial stress of column, the larger the value of J-integral. The fracture of specimens made of low fracture toughness steel can be explained by JIc fracture criterion. For steel of high fracture toughness, however, it is necessary to consider not only J-integral but also other fracture conditions such as elastic strain energy for brittle fracture after slow crack growth.