Seismic collapse of self-centering steel MRFs with different column base structural properties.

The effect of the strength and stiffness characteristics of a previously proposed novel column base on the seismic performance and collapse capacity of steel self-centering moment-resisting frames is evaluated in this paper. This is done through three normalised parameters that represent the initial stiffness, post-yield stiffness, and strength of the column base, which can be independently adjusted. For these evaluations, a prototype steel building, which serves as a case study, is designed with sixteen different cases of a self-centering moment-resisting frame with different column base stiffness and strength characteristics (SC-MRF-CBs). A self-centering moment-resisting frame with conventional column bases and the same members and beam-column connections as those of the SC-MRF-CBs, named SC-MRF, serves as a benchmark frame. A set of 44 ground motions was used to conduct non-linear dynamic analyses and evaluate the seismic performance of the frames. Incremental dynamic analyses were also performed with the same ground motions set to evaluate the collapse capacity of the frames. Collapse capacity fragility curves and adjusted collapse margin ratios of the frames were derived and used for the comparison of the seismic risk of the frames. The results show that the new self-centering column base significantly improves the seismic performance of the SC-MRF, demonstrating the potential of the SC-MRF-CBs to be redesigned with smaller member sections. Moreover, the SC-MRF-CBs achieve significant reduction in collapse risk compared to the SC-MRF. Finally, the results show that increasing the base strength and stiffness improves the seismic performance and collapse capacity of the SC-MRF-CBs.