The Role Of Epsilon For The Identification Of Groups Of Earthquake Inputs Of Given Hazard

This paper focuses on the identification of groups of uniform hazard (acceleration) timehistories for Performance Based Seismic Design applications. In detail, on the basis of a peculiar Probabilistic Seismic Hazard Analysis, the characteristics that a group of earthquake inputs must possess in order to be associated to a given exceedance probability are obtained. The proposed procedure takes advantage of the information carried by the “epsilon” parameter, and is rooted on a separate treatment of the aleatory variability and the epistemic uncertainty considered in the hazard analysis. The analytical developments allow to identify a condition for the spectral ordinates (“spectral cloud”) of the acceleration time histories, which is valid for a number of structural periods at once, and to quantify (in terms of coefficient of variation of the spectral ordinates) the randomness associated to the epistemic uncertainty (error in the spectral acceleration prediction law).