Updated evaluation metrics for optimal intensity measure selection in probabilistic seismic demand models

This study proposes an update on the criteria that are typically used to select the optimal intensity measures (IMs) for development of probabilistic seismic demand models (PSDMs), which relate the input seismic hazard and structural responses. Employing an optimal IM contributes to decreasing the uncertainty in the PSDMs, which, in turn, increases the reliability of the PSDMs used in performance-based earthquake engineering analyses. In the literature, the optimality of the IMs is generally evaluated by the following metrics: efficiency; practicality; proficiency, which is the composite of efficiency and practicality; sufficiency; and hazard computability. The present study shows that the current criteria for evaluating the practicality and proficiency features may mislead the selection of the optimal IM when IMs with different ranges and magnitudes are investigated. Moreover, the efficiency metric can provide biased results when comparing IMs for predicting demands of different structural components or types of systems. As a result, alternative solutions are proposed to investigate the efficiency, practicality, and proficiency features of the IMs. The suggested metrics are employed in a case study to evaluate the IMs used to develop PSDMs for multi-span continuous steel girder bridges in Texas subjected to human-induced seismic hazard.