Analysis of floor response spectrum in nuclear power plants taking into consideration uncertainty of ground motion input

The floor response spectrum has great significance for the seismic safety assessment of structures and equipments of nuclear power plant (NPP). Deterministic methods are generally employed to evaluate the floor response spectrum in NPP design. Taking into consideration of the randomness of earthquake occurrence, based on the seismic risk analysis of earthquake affected zone and the probability density of earthquake occurrence at the sites of NPP in China, by employing Monte Carlo probabilistic statistics method, the effect of seismic uncertainty on the dynamic response of NPP structure is investigated. As indicated by the results of numerical example, with a probability of nonexceedance no less than 90%, the peak value of floor response spectrum obtained by considering the aforementioned uncertainties is somewhat lower than that obtained by ignoring the uncertainties. The research results offer a better understanding of the conservatism in NPP design.