Optimal ground motion intensity measure for seismic assessment of high-rise reinforced concrete structures

Abstract

The ground motion intensity measure is a key parameter affecting the accuracy of probabilistic seismic demand analysis (PSDA). This paper uses the incremental dynamic analysis (IDA) results of 12 three-dimensional reinforced concrete (RC) high-rise structures to explore the efficiency and sufficiency of a spectral acceleration Sa(T) intensity measure (IM) in a continuous period T (0–8 s). Subsequently, the effects of higher modes and period softening on the results are investigated. Controlling periods – that is, the lower and upper bounds of periods – across the spectrum are also examined in order to propose an optimal IM Sa,GM that considers the effects of higher modes and nonlinear softening on the seismic responses of three-dimensional high-rise buildings. Finally, the proposed optimal IM Sa,GM is compared to the widely used IM of spectral acceleration at the first-mode period Sa(T1) of the structure and the improved IM Sa¯, which considers the first n modes in the field, based on the criteria of efficiency, practicality, sufficiency, proficiency, and scaling robustness. The results indicate that the efficiency and sufficiency of the IM Sa(T) fluctuate with increasing periods T and are affected by higher modes and period softening. Furthermore, the proposed optimal IM Sa,GM exhibits a significant decrease in dispersion with respect to the structural response (efficiency) and scores higher on sufficiency, practicality, proficiency, and effectivity robustness than the IMs Sa(T1) and Sa¯.