Seismic response of isolated nuclear power plant considering nonlinear restoring force characteristics of rubber bearings

Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi 

In Japan, applications of seismic isolation systems using rubber bearings to new generation Nuclear Power Plants (NPPs) and Fast Breeder Reactors (FBRs) have been considered in order to enhance seismic safety. However, the isolation performance will decline in case of huge earthquakes, because of nonlinearity of both horizontal and vertical restoring characteristics of rubber bearings. In addition, Probabilistic Safety Assessment (PSA) has been introduced to seismic design. However the application of PSA to seismic isolation has not been attempted yet, and accurate seismic response simulation of isolation system required for the application. Authors carried out seismic response analysis that considers both horizontal and vertical nonlinearity of rubber bearing. Influence of nonlinearity of rubber bearing upon response of building was investigated by the analysis.