Simulation of non stationary ground motion compatible withNGA-spectra

The modelling of seismic load is a major topic that has to be addressed thoroughlywhen performingtransient seismic analysis.A common approach, widely accepted also by the international seismic codes, is tosimulate artificial accelerograms whose mean or median response spectrum matches, within a certain toleranceand along a defined range of frequencies, a target response spectrum. However, recent ground motion attenuationmodels do not only provide median or mean values but come along with information on dispersion and spectralcorrelations (Baker & Jayaram 2008). Concurrently, common ground motion models based on power spectraldensities do not allow to simulate artificial accelerograms featuring all of the variability observed for recordedtime histories. In this paper, the information on dispersion and correlation of pseudo-spectral acceleration valuesis used in order to construct a probabilistic spectrum-compatible non-stationary power spectral density model.Samples of ground motion time histories can be simulated using the classical spectral representation theoremfor evolutionary power spectral densities.