Residual Axial Resistance of Cross-Shaped Steel-Reinforced Concrete Columns After Impact Loading: Experimental and Numerical Investigations

To investigate how lateral impact influences the residual axial resistance capacity of cross-shaped steel-reinforced concrete (CSRC) columns, the residual axial resistance test was carried out following impact test. A finite element model (FEM) was developed to simulate axial and lateral impact loading, and its accuracy was confirmed through comparison with test results. The analysis shows that the numerical model can simulate the impact force, deflection, deformation mode and residual axial resistance of the column with adequate accuracy. With the verified finite element models, the residual axial resistance (Nr) of CSRC columns under six different parameters was further analyzed. Results demonstrate that the column primarily undergoes flexural deformation under impact, whereas shear effects are localized at the impact zone. A higher structural steel ratio (α) and yield strength of the cross-shaped steel (q) contribute to improved Nr and reduced mid-span displacement (Δmax). With the increase in compressive strength of concrete (c) and axial compression ratio (n), the Nr increases to a certain level and then decreases, and the Δmax decreases first and then increases in a similar manner. The change in slenderness ratio (γ) in a small range can improve the Nr of the column, and the significant increase in γ results in instability and failure. In particular, when the slenderness ratio increases from 8 to 12, the residual bearing capacity of the column decreases by 19.4%. This study proposes a residual bearing capacity-prediction formula based on seven key influencing parameters, which shows high accuracy (R2 = 0.93). A damage evaluation index based on flexural bearing capacity (Ddag) is introduced, and the structural state is accordingly classified into four damage levels. Compared with conventional numerical simulations that typically require more than 3 h of computation time, the proposed method can rapidly complete the damage assessment of columns within 5 min, providing an efficient approach for structural safety evaluation and response strategies.