This study identified and quantified possible cliff edge effects through a seismic safety evaluation of a nuclear power plant, based on the concepts of risk and defense in depth. Cliff edges of the both physical and knowledge-oriented type were considered in this study. We investigated a seismic isolation effect, etc., for physical cliff edges, and the modeling of the target structure, boundary conditions, etc., for knowledge-oriented cliff edges.
Response analysis was performed using a sway-rocking (SR) model and a three-dimensional model of the target building. The seismic isolation effect of the base-isolated building was confirmed by comparison to the results of earthquake-resistant building. In the case of a collision with the retaining wall of the base-isolated building, the level of damage was found to depend on the modeling of the collision condition assumed. On the other hand, the study confirmed the differences between the results from the SR model and the three-dimensional model. And the greater fidelity of the three-dimensional model was also confirmed. This paper presents and discusses these results.