Engineering design earthquakes from multimodal hazard disaggregation: Fid-Bau Portal

Engineering design earthquakes from multimodal hazard disaggregation

Iervolino, Iunio / Chioccarelli, Eugenio / Convertito, Vincenzo

Abstract To define reference structural actions, engineers practicing earthquake resistant design are required by codes to account for ground motion likely to threaten the site of interest and also for pertinent seismic source features. In most of the cases, while the former issue is addressed assigning a mandatory design response spectrum, the latter is left unsolved. However, in the case that the design spectrum is derived from probabilistic seismic hazard analysis, disaggregation may be helpful, allowing to identify the earthquakes having the largest contribution to the hazard for the spectral ordinates of interest. Such information may also be useful to engineers in better defining the design scenario for the structure, e.g., in record selection for nonlinear seismic structural analysis. On the other hand, disaggregation results change with the spectral ordinate and return period, and more than a single event may dominate the hazard, especially if multiple sources affect the hazard at the site. This work discusses identification of engineering design earthquakes referring, as an example, to the Italian case. The considered hazard refers to the exceedance of peak ground acceleration and 1s spectral acceleration with four return periods between 50 and 2475 year. It is discussed how, for most of the Italian sites, more than a design earthquake exists, because of the modeling of seismic sources. Furthermore, it is explained how and why these change with the limit state and the dynamic properties of the structure. Finally, it is illustrated how these concepts may be easily included in engineering practice complementing design hazard maps and effectively enhancing definition of design seismic actions with relatively small effort.

Highlights ► Design scenarios from hazard disaggregation are investigated for engineering use. ► Maps of design earthquakes in terms of M, R and ε are shown for Italy. ► First design earthquake in most of cases is a close, moderate magnitude event. ► Dependency of design earthquakes on spectral and return periods was demonstrated. ► Discussion on possible practical applications of these results is provided.