The Criteria for Assessment of Seismically Damaged Degree of Buildings in Japan

Publisher Summary This chapter presents the damage classifications for the seismically damaged buildings including reinforced concrete structures, steel structures, and wood structures, as well as the guidelines published in Japan. During the last half century, Japan has encountered occasional major earthquakes that have resulted in a loss of not more than 50 human lives due to the collapse of buildings and slope instabilities, unfortunately, except due to tsunami disaster. In 1981, the Japanese earthquake resistant regulations were drastically revised, taking account of key dynamic characteristics of structures. Therefore, the guidelines for reinforced concrete (RC) structures and steel structures were published, giving instructions to retrofit structures. These guidelines provide procedures to estimate the seismic resistant capacities of structures, earthquake input forces, and strengthening techniques. They provide two levels of damage evaluation: rapid evaluation and overall damage classification including repairing techniques. Rapid evaluation begins with a quick visual inspection for the general level of damage, and then within a day or two, determines the building usability to avoid the potential damage due to aftershocks. The more detailed overall damage classification is done during at least about a week to about a month after deciding whether repairing and/or strengthening are needed for the long-term continued use of buildings, or whether a building should be demolished or removed. Prior to retrofitting, detailed planning is needed for the earthquake resistant capacities, costs, and building usability. Especially for the earthquake resistant capacities, a damage index is computed from a ratio of the structure's seismic index after and before an earthquake. Because the guidelines for the damage evaluation are to be applied at the emergency, it is urgently necessary to make the guidelines practical, and to train the structural engineers for the immediate and effective damage evaluation before disastrous incidents would occur.