Mitigating seismic response of RC moment resisting frames using steel energy-dissipative columns

A novel system of steel Energy-Dissipative Columns (EDCs) is proposed to mitigate seismic responses of reinforced concrete Moment Resisting Frames (MRFs). The EDC-MF dual system aims to not only dissipate seismic energy by replaceable steel strip dampers in EDCs but mitigate inter-story drift concentration to avoid soft/weak-story failure of conventional MRFs. A simplified numerical model of EDC-MF dual system is established by using lumped mass shear model for MRFs and finite element model for EDCs. Parametric studies are conducted to investigate the effect of storey number, stiffness ratio, soft story factor and seismic intensity factor on the mitigation efficiency of EDCs. The results show that the lateral stiffness ratio of EDC to MRF, the story irregularity factor of MRFs, and the ratio of story shear capacity of EDC-MF systems to seismic base shear are the most important parameters. It is found that both the maximum inter-story drift and the inter-story drift concentration can be effectively mitigated due to the presence of EDCs, compared to traditional MRFs. The mitigation efficiency of EDCs increases with increasing lateral stiffness ratio and story irregularity factor under various ground motion intensities. A rational range of lateral stiffness ratios of 0.02-0.2 is recommended for the seismic design of EDC-MF dual systems.