Alternative stochastic approaches to seismic response analysis

The importance of NPP structures justifies the adoption of the most advanced methods of analysis that are currently acceptable for engineering practice. Achievements in this field will be beneficial for other categories of structures too, for which the NPP field will play a role of field of pilot activity. Following developments are based on the principle that a satisfactory control of structural safety can be based only on a probabilistic approach. Two basic kinds of representations of seismic action must be considered in this context: representation of seismic motion during one event and representation of the expected sequence of events. The paper deals essentially with representations of the first category. Three basic representations are considered in this direction: stochastic (simplified), making use basically of second order covariance functions; time-history (essentially artificial accelerograms); and design spectra