A statistical study on the peak ground parameters and amplification factors for an updated design displacement spectrum and a criterion for the selection of recorded ground motions

The development of performance-based design methodologies and displacement-based approaches requires a special attention to the correct definition of the seismic input to be used for the analyses and in particular of reliable displacement response spectra. In this paper, the characterization of the schematized response spectra has been deeply investigated with the purpose of obtaining a more accurate displacement design spectrum and a simple but efficient criterion for the selection of recorded ground motions. First, a correlation analysis between peak ground motions parameters and other intensity measures has been performed. The independent parameters which are both necessary and sufficient for an engineering characterization of the seismic input at a specific site have been identified as the three peak parameters (PGA, PGV and PGD). Second, the amplification factors have been modeled as random processes in order to identify their fundamental properties in terms of mean values and variability. Based on the obtained results, an updated formulation for the design displacement spectrum is proposed and compared with that suggested by the Eurocode 8. Finally, a criterion for the selection of recorded ground motions for time-history analyses is presented.