Stochastic approach for the seismic design of nuclear power plant equipments

In this paper, the drawbacks of the classical seismic design process, in which inputs are defined in terms of response spectra, are underlined. Upon other author's studies, the outlines of an alternative stochastic approach are presented. In this new methodology, the ground input motion is described by its power spectral density (PSD) function. The PSD functions of the design parameters are obtained through transfer functions. Then, using the cumulative probability function of the maximum response proposed by Vanmarcke, design values are derived according to an acceptable probability of exceedance. For the example of a primary structure, the proposed method is applicable. In the case of secondary structures, comparisons with simulations show that those cumulative probability functions do not apply in all the cases. Essentially, that depends on the number and relative importance of the different peaks appearance in the PSD of the responses. (orig.)