Though the Kashiwazaki-Kariwa Nuclear Power Station was subjected to significantly strong ground motions of the Niigataken Chuetsu-oki Earthquake in 2007, the main facility buildings had almost no damage. Since a large amount of land subsidence was observed near the buildings, the soil around the buildings was expected to be in the strong nonlinear state during the earthquake. In this paper, the authors tried to clarify actual behavior of Unit No.7 reactor building during the earthquake through the simulation analyses using the finite element method. In our analyses, nonlinear effects were considered in contact conditions between the buildings and the surrounding soil by employing joint elements in addition to soil materials.
