Seismic performance of a ring beam connecting filled-tube columns with concrete frames

The seismic performance of a ring-beam connection system that integrates concrete-filled steel tubular columns and reinforced concrete frames was studied. Physical experiments on two fabricated specimens were conducted under monotonic and cyclic loading. The results showed the connection system had a displacement ductility ratio of 4.68 and an energy dissipation coefficient over 2.0. A finite-element model was established and the numerical and experimental results were compared in terms of skeleton curve and stiffness degradation trend. Parametric studies were then performed to evaluate the effects of axial compressive force ratio, concrete strength and reinforcement ratio for the ring-beam joint, and reinforcement ratio for the frame beam, on the seismic performance of the proposed connection system. The results indicated that the increase in the axial compression ratio or strength of the concrete material would improve the initial stiffness and strength of the connection system. However, the effect of the ring-beam joint reinforcement ratio and frame beam reinforcement ratio of the connection system on the seismic performance was negligible.