On the evaluation of probabilistic displacement spectra

In this paper, on the basis of a large set of ground motion records, the result of a statistical analysis on the elastic displacement spectra and the comparison between different theoretical probabilistic distribution will be presented for a selected number of vibration periods. The following four theoretical distributions have been taken into account: Normal, Lognormal, Gamma and Gumbel type I. Since the best fit to the data was provided from the Lognormal distribution, in this paper lognormal displacement spectra will be defined, for different levels of probability of non-exceedance, for the estimation of the displacement demands to structures located on different local soil condition, at different distance from the causative fault, and for different levels of magnitude.