Probabilistic Seismic Hazard Analysis: Identification of Design Earthquake Inputs

In recent years, Performance Based Seismic Design (PBSD) has played a central role for re-search works in the field of seismic engineering. The core idea of the PBSD is the probabilistic assessment of the structural performances due to seismic action [Bertero and Bertero 2002, Moehle and Deierlein 2004, Zhang et al. 2004]. From a practical point of view, following the PEER framework [Cornell and Krawinkler 2000], this assessment can be achieved through an articulated procedure which can be summarized in the following subtasks [Zhang et al. 2004]: · Probabilistic Seismic Hazard Analysis (PSHA) or simply Hazard Analysis (HA); · Probabilistic Seismic Demand Hazard Analysis (PSDHA); · Probabilistic Seismic Capacity Analysis (PSCA) also called Fragility Analysis; · Seismic Reliability Analysis (SRA). As pointed out in recent scientific contributions [Giovenale et al. 2004] the main shortcoming which prevent the effective application of such a approach currently lies in the large dispersion (i.e. large variability) of the structural response (as evaluated through properly chosen Damage Measure DM or Estimated Damage Parameters EDP) obtained from non-linear dynamic analy-sis which uses as input selected earthquake acceleration time histories. This paper focuses mainly on the correct identification of the dynamic inputs (“bins” as defined by Giovenale et al. [2004] or “EPI groups” as defined hereafter by the authors) to be used in the PSDHA subtask. In detail, the paper introduces a general framework (“methodology for EPI group creation”) for the rationally-organised treatment of the latest contributions in terms of ground motion parameters which have a substantial effect upon the structural response. Moreover, this paper (a) compares the results which can be obtained following different rules for the application of the methodology proposed, (b) identifies a practical proposal for the ef-fective application of the methodology based upon the use of a vector-valued IM composed of Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV), (c) proposes the use of “representative” EPI groups characterised by a (1) a vectorial IM composed of PGA and PGV and (2) a specific relative ratio of near-field records to far-field records.