Zhuojin Pipe Fitting Co., LtdLateral Impact Test and Finite Element Analysis of Hollow Sandwich Stainless Steel CFST Members
Literature Overview
This study by Jiang Shan and Wang Rui from Taiyuan University of Technology, published in Industrial Construction (2016, Vol. 46, No. 11, pp. 161-167), investigates the lateral impact behavior of hollow sandwich stainless steel concrete-filled steel tubular (CFST) members through both experimental testing and finite element analysis. Funded by the National Natural Science Foundation of China (51379290), this research addresses an important structural engineering concern: the impact resistance of composite members used in protective structures, bridge columns, and critical infrastructure.
Core Technical Concepts
The hollow sandwich CFST member is a composite structural system consisting of an outer stainless steel tube, a concrete core, and an inner steel tube, with a hollow space between the concrete core and the inner tube. This configuration combines the corrosion resistance of stainless steel with the high compressive strength of concrete and provides a hollow interior that can accommodate utilities or reduce self-weight.
Six test specimens were designed across three impact conditions using the DHR9401 drop-weight impact testing machine. The impact height was varied to simulate different impact energy levels, and the hollow ratio was varied to study the effect of the internal hollow space on impact performance. The tests recorded impact force time-history curves, overall residual deformation, and failure modes.
Experimental Results and Parametric Analysis
The experimental results reveal clear trends in impact behavior that have direct implications for design. As impact height increases, the impact force plateau value, impact duration, overall deformation, and local deformation all increase. This is expected from basic energy balance considerations, as higher impact heights correspond to greater kinetic energy that must be absorbed by the structural member.
| Parameter Variation | Effect on Impact Performance | Trend |
|---|---|---|
| Increasing Impact Height | Increases force plateau, duration, and deformation | Positive correlation |
| Increasing Hollow Ratio | Destabilizes plateau phase, eliminates peak phase | Negative correlation with impact resistance |
The hollow ratio effect is particularly important. As the hollow ratio increases, the plateau phase of the impact force curve becomes increasingly unstable, and the peak phase gradually disappears. This indicates a fundamental degradation of impact resistance, as the member loses its ability to absorb energy in a controlled, ductile manner. The hollow space reduces the effective concrete cross-section and the confinement interaction between the steel tubes and concrete core.
Finite Element Analysis Validation
A finite element analysis model was developed using ABAQUS software and validated against the experimental results. The comparison between numerical and experimental results shows good agreement, confirming the reliability of the finite element model for predicting impact behavior. This validation is important because it enables parametric studies and design optimization through numerical simulation, which is more efficient and economical than physical testing.
The finite element model must accurately capture several complex phenomena: the nonlinear behavior of stainless steel under impact loading, the confinement effect of steel tubes on concrete, the interaction between the hollow space and the concrete core, and the local deformation patterns that develop during impact. The good agreement between simulation and experiment suggests that the model successfully captures these phenomena.
Engineering Practice and Design Implications
From a practical engineering perspective, this research provides important guidance for the design of hollow sandwich CFST members subjected to impact loading. The hollow ratio must be carefully controlled to maintain adequate impact resistance. The study suggests that there is an optimal hollow ratio beyond which the impact performance degrades significantly, and this ratio should be determined through a combination of experimental data and validated finite element analysis.
The use of stainless steel for the outer tube provides excellent corrosion resistance, which is particularly valuable for members exposed to harsh environments such as marine structures, chemical plants, or infrastructure in regions with de-icing salts. However, the higher cost of stainless steel must be justified by the improved durability and impact performance.
The validated finite element model is a valuable tool for engineering design, enabling the prediction of impact performance for different geometric configurations and material combinations. This capability is essential for optimizing the design of hollow sandwich CFST members for specific impact loading scenarios, such as vehicle impacts on bridge columns or blast loading on protective structures.
This research provides a solid foundation for the understanding and design of hollow sandwich stainless steel CFST members under lateral impact loading. The combination of experimental validation and finite element analysis offers a comprehensive approach to characterizing impact behavior, and the parametric study results provide practical design guidelines. Engineers involved in the design of impact-resistant structures, protective buildings, and critical infrastructure should consider the hollow sandwich CFST concept as a viable structural system, provided that the hollow ratio is carefully controlled to maintain adequate impact resistance. The corrosion resistance of stainless steel further enhances the long-term durability and service life of these members in demanding environments.