Study on seismic performance of a rocking steel frame structure with buckling-restrained columns

To avoid damage localization effect in steel frame structures and enhance the structural energy dissipation capacity, a rocking steel frame with buckling-restrained columns (RSFB) was formed by replacing the side steel columns at the bottom story with buckling-restrained braces (BRBs). The buckling-restrained columns (BRCs) firstly yield to dissipate energy under a rare earthquake, and the rest parts of the steel frame remain elastic and rotate around the base of the middle column to control the deformation of the structure. A pseudo-static test was conducted for an RSFB model, the test phenomena and analysis results show that the larger out-of-plane deformation occurs in the steel frame and embedment portions of BRC due to the failure of the out-of-plane restraints. The capacity of the BRC on the compression side cannot be fully used, and the pinching effect is observed in the structural hysteretic loops. However, the BRC in the tension side can work normally, and the structural lateral carrying capacity is not fully lost. A multi-scale finite element model was established and validated by the test results. The seismic performance of RSFB with full out-of-plane restraints (RSFB-FOR) was investigated based on the validated numerical model. The simulation results show that the hysteretic loops of RSFB-FOR are plump under the cyclic loads, the structural lateral inter-story drift is uniformly distributed, and the plastic deformation is mainly concentrated in the energy dissipating portion of BRCs, showing that the proposed RSFB can achieve good seismic performance. Finally, the influence of the arrangement direction of strong axis of BRC in RSFB on the structural seismic performance was investigated, and the results show that the stability and energy dissipation capacity of RSFB can be enhanced by rotating strong axis of BRC by 90 degrees.