Abstract：The collapse of building structure is characterized with discrete and systematic features, indicating that the study of seismic collapse of buildings shall be conducted from multi-parameter and multi-level aspects. Three 1/3-scale models of three-story, three-bay reinforced concrete plane frames were fabricated and tested under low-cycle loading, based on the research of structural collapse and failure mode. The effects of axial compression ratio and beam-to-column linear stiffness ratio on the seismic performance of RC frame structures were discussed through the analyses on failure process, failure pattern, energy dissipation capacity and stiffness degradation of model frame, which provides references for further researches. Test results indicate that the ideal beam-hinge failure mechanism of RC frame structures can be easily attained by reducing vertical axial force and beam-to-column linear stiffness ratio, which shall be beneficial to the full development of plastic hinges at beam ends. The ultimate failure of test frames was caused by the sudden crushing of concrete owing to the full development of plastic hinges at column bottoms in the first floor, and the energy dissipation capacity of components in the first floor was fully utilized, while those of second floor and third floor were relatively less. The peak load, ultimate load and equivalent viscous damping coefficient of KJ-2 were about 9.9%, 8.7% and 16.5% larger than those of KJ-1 respectively, but the displacement ductility coefficient of KJ-2 was about 57.1% smaller than that of KJ-1, indicating that the bearing capacity and energy dissipation capacity of a structure can be increased by increasing its vertical load, but the ductility and deformation capacity may be decreased. Meanwhile, increasing the vertical load to some extent shall be beneficial to enhancing the initial lateral stiffness of structures and postponing the structural stiffness degradation, but the P-Δ effect appears to be prominent in the case of large inter-story drift angle. By increasing the linear stiffness ratio of RC frame structures, the energy dissipation capacity can be enhanced, but the bearing capacity, ductility and initial lateral stiffness of structure may be reduced. For the beam-hinge structure with small axial compression ratio and beam-to-column linear stiffness ratio, the inter-story drift angle of structure when approaching to collapse can reach 1/25, and the structures still possess a certain load-bearing capacity at this stage.
