Mechanical analysis of steel tube-confined reinforced concrete double-column piers

To study the seismic performance of steel tube-confined reinforced concrete (STCRC) double-column piers, numerical models for two steel tube split configurations (Mode A and Mode B) were established in ABAQUS, to systematically analyze the effects of axial compression ratio and other parameters. Stiffness degradation is typically governed by the axial compression ratio, and split patterns show negligible effects. Numerical simulations accurately replicate experimental failure modes, thereby confirming the plastic hinge formation at predicted locations. Mode A is characterized by the plastic hinge forming at G1, while in Mode B, due to the introduction of a mid-height slit, the plastic hinge shifts to G2. Parametric studies reveal strong linear correlations between the peak lateral load capacity and the three key parameters (connecting plate height, reinforcement ratio, and axial compression ratio), while concrete strength and steel properties exhibit relatively weaker effects. The proposed simplified theoretical model can accurately predict the lateral load capacity, with errors not exceeding 8% compared to experimental results, demonstrating promising accuracy and application potential.