Experimental study on the seismic behavior of RC columns improved with central large-diameter butted steel rods

A reinforced concrete (RC) column improved with central large-diameter butted steel rods (CLBSR column) has been proposed to increase the limit value of the axial compression ratio. This paper presents the seismic behavior analysis of CLBSR columns subjected to low-cycle reciprocating loading. The CLBSR columns were also compared with the RC column improved with central large-diameter steel rods (CLSR column) and the RC column improved with central reinforcement bars (CRB column) under the same experimental conditions. The typical failure modes, hysteretic curves, skeleton curves, stiffness degradation, and energy dissipation capacity were all investigated. The improved PARK damage model obtained the corresponding relationships between the damage indices and the damage state of each column. The test results indicated that the CLBSR columns and CLSR columns had similar seismic behavior, but were slightly inferior to the CRB columns. Overall, the butt joint of large-diameter steel rods had little effect on the seismic behavior.