Round-ended concrete-filled steel tube (RE-CFST) members, commonly used in bridge piers and main towers, are often subjected to impacts from vessels, vehicles, floating debris, and other potential collisions. Therefore, this study focuses on the residual mechanical performance of RE-CFST columns exposed to the combined effect of eccentric compression and impact loading. Post-impact compression tests were conducted, and the failure modes, load-midspan displacement, and load-longitudinal strain curves under different eccentricity ratios and axial-load ratios were obtained. The results showed that the RE-CFST beam-columns primarily presented global deformation under lateral impact. Under eccentric compression, pronounced local buckling was observed in the outer steel tube on the compression side. The load-lateral displacement curve of the column under eccentric compression showed a gentle decrease, indicating good ductility of the specimen. As the eccentricity ratio and axial-load ratio increased, the residual bearing capacity of the specimen decreased. In addition, using ABAQUS software, a total of 144 finite element (FE) models were established to analyze the lateral impact behavior and residual bearing capacity of RE-CFST columns. The effects of impact velocity, eccentricity ratio, axial-load ratio, aspect ratio, and steel ratio were emphatically studied. Results indicate that with the increase in steel ratio and aspect ratio, the post-impact residual deflection of the specimens decreases, while the residual bearing capacity improves. Finally, based on response surface analysis, formulas for the residual deformation after an impact and residual bearing capacity coefficients of these specimens under the interaction of multiple factors were proposed. The results show that the aspect ratio is a key factor affecting both post-impact residual deflection and residual bearing capacity coefficients. Furthermore, the interaction between aspect ratio and eccentricity ratio, as well as between aspect ratio and impact velocity, is significant. The proposed formulas can well predict the post-impact residual deformation and residual bearing capacity coefficients of RE-CFST columns.

H-section steel columns have been widely employed in industrial buildings and parking lots, etc., which are vulnerable to crane-loading or vehicle collisions. Based on above background and previous experimental studies, the lateral impact model and residual load-carrying capacity model are established by using Abaqus finite element software to analyze the performance of H-section steel columns during and after impact loading. Firstly, the working mechanism, including the deformation characteristics, stress evolution and energy dissipation, is analyzed. Results indicate that under impact loading, the deformation pattern is mainly dominated by the global deformation, with the local deformation of the upper flange and out-of-plane buckling of the web. The time history curve of impact force exhibits an obvious plateau phase, and the existence of the pre-axial compression clearly reduces the impact resistance of the specimens. In general, H-section steel columns present favorable ductility performance during impact loading. Subsequently, a total of 108 parametric models are constructed, and the effects of load parameters (impact mass, impact velocity and axial load ratio), material parameter (steel yield strength) and geometric parameters (sectional area and specimen length) on the impact force, deformation, and residual load-carrying capacity are emphatically studied. The results show that as the impact mass, impact velocity, and/or pre-axial loading ratio increase, both the global and local deformations of H-section steel column will increase, while the residual load-carrying capacity will decrease. Finally, by considering the multi-factor interactions, the formulas for predicting global deformation and local deformation during impact and the residual load-carrying performance after impact are proposed by using response surface method. Results show that pre-axial loading is a key factor affecting global deformation, while the impact velocity mainly affects local deformation. In addition, both the pre-axial loading and impact velocity significantly interact with other parameters. The proposed formulas can be employed for the damage evaluation and design of H-section steel columns during the whole impact process and after impact event.