Generation of spectrum compatible site-dependent earthquake load histories by evolutionary approach

In this work a generation procedure for sets of simulated accelerograms is formulated on the basis of an assigned target design spectrum. The proposed approach accounts for both energy release and frequency content variability in time. The discussed evolutionary model is based on the assumption of decoupling the distribution in time of the energy release from the changing of the frequency content that is obtained by means of an amplitude modulation function and a frequency modulating function. The decoupling of the two main sources of the non-stationary behavior of natural time-histories allows the recognition of strict relations between recorded accelerograms at a site and the underlying evolutionary model here proposed. The numerical example is based on a specific record at a reference Italian seismic site and on the corresponding design spectrum from the national design code.