Experimental and Numerical Study on the Behavior of RC Members under Combined Loads

In this paper, we present an investigation of the performance of reinforced concrete (RC) columns under combined bending loads and various axial forces using a finite element method (FEM) model developed with the ABAQUS finite element program, verified with actual experimental values. In the experimental study, we applied combined bending loads and various axial forces to four RC members. Two RC members were subjected to vertical cyclic loads using displacement control with 0% axial force, while the other two were tested with vertical cyclic loads, one with 10% axial force, and the other with 20% axial force. The axial force load was applied using a specially designed setup. The experimental results of the RC members include observations of final failure mode, ductility, and axial load–bending moment interaction curves (P–M correlation curves). The experimental study confirmed that as the axial force increased, cracks in the RC columns concentrated at the center of the column. The yield strength increased by 55% when the axial force ratio was 10%, and 106% when the axial force ratio was 20%. The maximum strength increased by 28% with a 10% axial force ratio, and 50% with a 20% axial force ratio. However, ductility tended to decrease as the axial force increased, reducing by 26% with a 10% axial force ratio and 60% with a 20% axial force ratio. The analytical study produced results consistent with the experimental research, showing similar numerical trends. Finally, when comparing theoretical values, experimental results, and analytical results using P–M correlation curves, we found that the experimental value has a safety rate of 18% compared to the theoretical value. The experimental and theoretical result values were similar. Therefore, it has been demonstrated experimentally and analytically that the current design has a safety value of about 18% for the performance of the actual structure.