Dynamic Response of Hollow Box Steel Tube Concrete Composite Columns Under Lateral Impact

Research Background and Methodology

Jia Zhilu and Wang Rui from Taiyuan University of Technology conducted a comprehensive investigation into the impact resistance of hollow box steel tube concrete composite columns. These hybrid columns combine reinforced concrete with steel tube concrete, offering enhanced structural performance for applications in buildings, bridges, and infrastructure vulnerable to blast, vehicle impact, or seismic loading. The study employed a self-developed drop-weight impact testing machine to conduct experimental investigations, supplemented by finite element analysis using ANSYS/LS-DYNA software.

The experimental program systematically varied three key parameters: boundary conditions (simply supported versus fixed-ended), impact height (representing impact energy levels), and axial compression ratio. The hollow box section geometry was selected to optimize weight efficiency while maintaining structural integrity. The research was supported by the National Natural Science Foundation of China and Shanxi Provincial Excellent Youth Fund, reflecting its significance in structural engineering research.

Key Experimental Results

The impact force time-history curves exhibited a notable evolution with increasing impact height. At lower impact energies, the curves displayed a two-stage pattern, transitioning to a three-stage pattern at higher energies. This transition indicates that the inner embedded steel tube concrete component begins to participate significantly in load-bearing only after the outer reinforced concrete layer has been substantially engaged. The mid-span displacement increased nonlinearly with impact energy, with the rate of displacement growth accelerating at higher impact heights.

The finite element analysis revealed the internal energy distribution among structural components. At high impact energy levels, the steel tube concrete component absorbed approximately one-third of the total impact energy, demonstrating its substantial contribution to the overall impact resistance. The energy absorption mechanism involves plastic deformation of the steel tube, concrete crushing, and friction between the steel and concrete interfaces.

Finite Element Model Validation and Component Energy Analysis

The LS-DYNA finite element model was calibrated against experimental data, showing good agreement in predicting impact force time-history curves and displacement responses. The model incorporated appropriate constitutive models for concrete (including strain rate effects) and steel materials, along with contact algorithms to simulate the steel-concrete interaction. The hollow box section geometry was accurately modeled to capture the complex stress distribution within the composite cross-section.

The energy distribution analysis is particularly valuable for structural engineers designing impact-resistant structures. The finding that the steel tube concrete absorbs up to one-third of the impact energy suggests that this hybrid design effectively utilizes the ductility and energy absorption capacity of the steel tube concrete component. The boundary condition effect — with fixed ends providing better performance than simply supported ends — aligns with classical structural mechanics principles but is quantified here under dynamic loading conditions.

Engineering Practice Considerations

For practical applications, this research provides several important design guidelines. First, the hollow box configuration offers a weight-efficient solution for impact-resistant columns without sacrificing structural capacity. Second, the relatively insensitivity to axial compression ratio suggests that these columns can be designed with a range of axial loads without significant compromise in impact performance. Third, the boundary condition design is critical — engineers should aim for fixed-end connections where feasible to maximize impact resistance.

From a fabrication standpoint, the hollow box steel tube concrete composite column requires careful attention to the welding quality of the steel tube components, the concrete placement and compaction within the steel tube, and the interface treatment between the reinforced concrete and steel tube concrete sections. Welding defects such as incomplete fusion or porosity in the steel tube joints could significantly reduce the impact resistance predicted by the analysis. Engineers should implement rigorous non-destructive testing protocols, including ultrasonic testing and radiographic testing, to ensure weld integrity in these critical structural components.

Study Insights and Outlook

This research effectively bridges experimental investigation and numerical simulation to provide a thorough understanding of the dynamic behavior of hollow box steel tube concrete composite columns. The systematic parametric study offers practical guidance for engineers designing impact-resistant structural systems. The finding that impact force curves evolve from two-stage to three-stage patterns with increasing energy provides a useful diagnostic tool for assessing structural damage states. Future research should explore the effect of repeated impact loading, the influence of environmental factors such as temperature and corrosion on impact performance, and the development of simplified design formulas for practical engineering use. The combination of experimental and numerical approaches demonstrated in this study sets a strong methodological example for structural impact research.