Seismic Fragility of Base-isolated Nuclear Power Plant Structures Considering Spatially Varying Ground Motions

摘要

The amplitudes and phases of the seismic ground motions change significantly over extended distances. Therefore, the spatial variation of ground motions has an important effect on the responses of long structures and foundations such as nuclear power plants (NPPs). The study presents the seismic fragility analysis of a base-isolated structure under the spatially varying ground motions. In this study, the base-isolated NPP with a total height of 65.8m and hemispherical dome is modelled as a lumped mass stick model. The structural NPP stick model and the nuclear island base mat are established by installing 121 lead rubber bearing (LRB) base isolation. The ground motions incoherency is performed using an isotropic frequency-dependent spatially correlation function. The seismic fragility of BI-NPP are investigated under the uniform excitation in addition to considering the spatially varying ground motions. The fragility curves are estimated for three limit states representing the design displacement of the base isolation. Thereafter this study emphasize the need of consideration of spatial variation in seismic design codes more practically for base-isolated nuclear power plants.