Seismic intensity measure selection considering Record-to-Record and Angle-to-Angle uncertainties.

This study addresses the critical task of selecting an appropriate seismic intensity measure to assess structural performance under earthquake loading. It explores the impact of intensity measure selection on two significant sources of uncertainty: Record-to-Record (R-to-R) and Angle-to-Angle (A-to-A) variability. While R-to-R variability has been extensively studied, A-to-A variability remains relatively unexplored. A large set of Intensity Measures are evaluated and compared in terms of their Record-to-Record Efficiency and Angular Efficiency. This study aims to provide a more comprehensive understanding of their suitability, regarding the simultaneous impact of mentioned uncertainties. Numerical analyses are conducted on two moment-resisting steel frame structures subjected to a diverse set of ground motions along with ten rotation angles. The efficiency of different intensity measures is computed, among which Ev indicated an acceptable performance in reducing the parallel randomness in probabilistic seismic performance assessment.