Analyzing and Comparing the Floor Response Spectra of the NPP Based on Different Soil Dynamic Numerical Models

The traditional soil dynamic impedance models, recommended by the main international seismic design codes of the nuclear power plant (NPP), are only expressed by a single parallel connection system of spring and dashpot which can not reflect the dynamic stiffness varying with excitation frequencies, and also can not simulate the cases of non-homogeneous site conditions. With the recent development of soil-structure interaction (SSI) analysis, based on the damping-solvent extraction method (DSEM) and the lumped parameter models recommended by seismic design codes of ASCE4-98,RCCG which are all applicable to the homogeneous site and also massless foundation model and viscous-spring artificial boundary model of especially fit for the numerical simulation of non-homogeneous site, comparative study of both the direct method and sub-structure method is carried out in this paper. Finally, by taking the analysis of floor response spectra (FRS) for a certain CPR1000 reactor building as an example, comparative analyses of homogeneous and layered site conditions using various soil dynamic numerical models above-mentioned are performed. In addition, in order to validate the accuracy, the calculated results are compared to that of SASSI program. The results show that FRS in the horizontal direction are good agreement regardless for the homogeneous and layered site conditions, the shapes of FRS in the vertical direction change obviously in the homogeneous site condition. This paper provides some guidance and reference in the aspect of evaluation the seismic suitability for the site of nuclear power plant (NPP).