Damage Due to Earthquakes and Improvement of Seismic Performance of Reinforced Concrete Buildings in Japan

Japan, which is one of the most earthquake prone countries in the world, has suffered from damaging earthquakes repeatedly and learned lessons from damages. First, history of damages to existing reinforced concrete (RC) buildings due to previous earthquakes and seismic code revision are summarized. Secondly, basic concept and procedure of Japanese seismic evaluation method were outlined and seismic capacity index, I s , of buildings suffered Kobe Earthquake. Strong correlation between damage level and seismic capacity index, I s , was found. After the 1995 Kobe Earthquake, the law for promotion of seismic evaluation and retrofit was enforced based on the lessons learnt from the damage and investigation. Seismic evaluation and retrofit were widely applied to existing RC buildings in all over Japan and contributed to improvement of seismic capacities of existing RC buildings designed by old seismic code. The improvement was proved by recent major earthquakes such as 2011 Tohoku Earthquake and 2016 Kumamoto Earthquake. Typical damage pattern, failure modes and tendency in each earthquake were introduced and effectiveness of seismic evaluation and retrofit was discussed.