建築物の耐震改修促進法改正と政策の展開

Abstract

The Building Standards Act was enacted in 1950 to promote safe buildings in Japan. In 1981, the seismic code was largely revised, requiring that buildings would not collapse, causing casualties, under a JMA seismic intensity of scale 6 upper. Buildings built before 1981 adopting the old seismic code but not the new one are classed as “existing non-conforming buildings”. These buildings do not conform to the new seismic code, however, damage to buildings built before 1981 caused by the Great Hanshin-Awaji Earthquake in 1995 was much greater than that to buildings constructed after 1981. This resulted in the enactment of Building Retrofitting Promotion Act in 1995, which aims to promote anti-seismic performance checks and seismic retrofits.This paper shows the situation of current retrofitting and policy development. It indicates the situation of administrative guidance to owners of about 90, 000 specific buildings not constructed to an anti-seismic design. It is significant to promote seismic retrofits for houses that constitute the majority of buildings. In 2003, the total number of houses was estimated to be about 47, 000, 000, of which about 18, 500, 000 were built before 1980. 11, 500, 000 of these are estimated to be vulnerable to earthquakes. As a policy development, the target is to increase the current seismic retrofit rate of 75% to 90% by 2015. To achieve this, the Building Retrofitting Promotion Act has been amended, and retrofitting is being promoted by local governments, strengthening administrative guidance to owners of specific buildings, providing support and financing for seismic retrofits, as well as support through the tax system.