Seismic Damage of and Seismic Rehabilitation Techniques for Railway Reinforced Concrete Structures

The Miyagi Prefecture Earthquake in 1978 was the first earthquake to cause serious damage to railway concrete structures in Japan. This was followed by the South Hyogo Prefecture Earthquake in 1995, which caused shear failure of columns of RC viaducts carrying the Shinkansen (Bullet Train) and old railroad lines predating the 1983 seismic design standard. As the result of various concrete structures sustaining extensive damage never experienced before, the seismic design standard was greatly revised, and the seismic rehabilitation of existing structures was started on a full scale. Basic concept of seismic rehabilitation is to prevent shear failure of columns that led to the collapse of RC viaducts and bridges catastrophically occurred in whole structural frame during the past large earthquakes. To enhance the seismic capacity of the whole structural frame, increase in ductility of each column through seismic rehabilitation capable of absorbing seismic energy is needed. As the space under many railway viaducts is used by stations and shops, negotiations regarding the relocation of businesses, the removal of large obstacles such as heavy machinery, and the development of valid seismic rehabilitation methods to reinforce a large number of massive columns were called for. At present, we are trying to enhance seismic capacity as much as possible for new structures in order to prevent serious damage and enable early restoration.