Seismic fragility curve estimation using signals generated with GMPE - Case study on the Kashiwazaki-kariwa power plant

Overview & Synopsis

As one of the participants to the international KARISMA Benchmark, we had conducted soil-structure interaction analysis on the Unit 7 reactor building of the Kashiwazaki-Kariwa nuclear power plant (Japan) using a full 3D finite element model. In this paper, we focused on the uncertainty propagation through the soil-structure system. For this purpose, a simplified model representing the largely embedded reactor building has been used for computation efficiency as a large number of numerical simulations were necessary.Seismic signals generated with NGA GMPE according to the July 2007 NCO earthquake scenario have been used to estimate the fragility curves. In the process, soil non-linearity caused by each seismic signal has been taken into account using the equivalent linear method. The results suggest that defining the control point of the input motion at the soil surface as prescribed in the French nuclear practice is not appropriate and may lead to biased results when performing non-linear soil-structure fragility analysis. The control point should be defined at the outcropping bedrock level.