A new global damage index for steel moment resisting frames based on two steps pushover analyses

Abstract

This paper proposes a new global damage index (DI) to evaluate and quantify the overall damage state induced by near-fault ground motions to the steel structures. DIs are conventional tools that evaluate and quantify the level of damage caused by earthquake excitement. The proposed damage index is based on two steps pushover analyses, which use roof residual drift ratio and maximum base shear before and after the earthquake. Moreover, the proposed damage index was compared with several well-known damage indices. Six steel moment resisting frames from 6- to 21-story frames were used for the evaluation. The strength and stiffness degradation were applied to all models as well. The incremental dynamic analysis was performed on the frames for 36 near-fault ground motions (a total number of 3312 nonlinear time history analyses) in the OpenSEES platform. The results show that the proposed DI can evaluate the damage properly in the nonlinear zone and collapse area in any nonlinear modeling methods. In addition, the merits and drawbacks of the proposed and other evaluated DIs were also discussed, and some of those drawbacks are being studied by the authors to be overcome in future works. Moreover, the efficiency of the proposed DI is also compared with the other studied DIs and shows that the proposed DI is significantly more efficient. The selected OpenSEES example files for the present study are shared through the link provided in the text.