Xiang Zhu

This study investigates the residual bearing capacity (RBC) of steel slag‐based artificial aggregate concrete‐filled steel tube (SA‐CFST) following impact loading through experimental and numerical analyses. The experiment examines the failure modes of SA‐CFST during impact and the axial load–displacement curves after impacts. Finite element models are subsequently developed to analyze the influence of key parameters on RBC of SA‐CFST columns. A comparative analysis evaluates the differences in RBC among SA‐CFST, concrete‐filled steel tube (CFST), and reinforced concrete (RC) columns. The results indicate that deformation in the residual capacity tests is primarily localized at the impact point. RBC decreases with increasing impact energy or reduced boundary constraints. The axial compression ratio ( n ) below 35% of compression capacity has a beneficial effect on the RBC of SA‐CFST, whereas exceeding this threshold produces adverse effects. Excessive axial load leads to reduction in RBC. Under the same conditions, the RBC of SA‐CFST is slightly lower than CFST, with a difference of less than 10%. In comparison, SA‐CFST demonstrates 30%–60% higher residual capacity compared to RC columns, and this advantage becomes more pronounced with increasing impact energy. SA‐CFST members are proven to have excellent RBC after impact, making them suitable for use in structures prone to collisions.

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 (N_r) 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 N_r and reduced mid-span displacement (Δ_max). With the increase in compressive strength of concrete (c) and axial compression ratio (n), the N_r increases to a certain level and then decreases, and the Δ_max decreases first and then increases in a similar manner. The change in slenderness ratio (γ) in a small range can improve the N_r 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 (D_dag) 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.