Axial Compressive Performance of Square Hollow Stainless Steel Tube Concrete Short Columns

Literature Overview

This paper by Tang Hongyuan, Liao Jing, Liu Ruizhong, and Hu Xiaowei, published in the Journal of Southwest Jiaotong University in 2023, investigates the axial compressive bearing capacity of square hollow stainless steel tube concrete short columns. The study was supported by the Ministry of Education Chunhui Program Cooperation Project (Z2016156). The authors conducted axial compression tests on six groups of specimens, varying the stainless steel outer tube thickness and concrete strength as key variables. The research aims to promote the application of square hollow stainless steel tube concrete components in civil engineering, a topic of growing interest due to the excellent corrosion resistance and sustainability advantages of stainless steel in structural applications.

Core Technical Points and Test Results

The experimental program was designed to systematically evaluate the influence of three primary parameters on the ultimate bearing capacity of the short columns: the width-to-thickness ratio of the stainless steel square tube, the core concrete strength, and the constraint effect coefficient of the stainless steel tube. The specimens were tested under axial compressive loading, and the researchers recorded the failure modes, load-displacement curves, and load-strain curves for each group.

The results demonstrated that reducing the width-to-thickness ratio from 34.9 to 20.9 resulted in an average 98.5% improvement in ultimate bearing capacity, highlighting the critical role of local buckling resistance in determining column strength. The increase in core concrete strength from C40 to C60 yielded a more modest 7.3% improvement, suggesting that the stainless steel tube geometry is a more influential factor than concrete strength alone. The constraint effect coefficient showed a near-linear relationship with ultimate capacity, confirming that the confining action of the stainless steel tube is a dominant mechanism in enhancing concrete strength.

Failure Modes and Constraint Effect

The failure modes observed in the tests revealed that specimens with higher width-to-thickness ratios experienced premature local buckling of the stainless steel tube before the concrete core reached its full compressive capacity. In contrast, specimens with lower width-to-thickness ratios exhibited more ductile failure patterns, with the stainless steel tube effectively confining the concrete core throughout the loading process. The researchers also discussed the influence of chamfering on the strength and ductility of the specimens, finding that chamfer geometry can significantly affect the stress distribution at the corners of the square tube.

A notable contribution of this paper is the development of a minimum thickness calculation method to prevent the inner tube from buckling before the outer tube. This is particularly relevant for composite columns where multiple tubes are used, as premature buckling of an inner tube can compromise the structural integrity of the entire assembly. The proposed calculation method provides a practical tool for engineers designing multi-tube stainless steel composite columns.

Standards and Specification Comparison

The authors compared their proposed compressive capacity calculation formula against existing simplified models from the literature and the calculation results from major international codes and specifications. This comparison is essential for validating the proposed formula and determining its applicability within existing regulatory frameworks. The relevant standards include the Chinese national standard GB 51225 for steel-concrete composite structures, the Eurocode 4 (EN 1994-1-2) for composite construction, and the Japanese AIJ recommendation for steel-concrete composite structures.

The proposed formula demonstrated good predictive accuracy for square hollow stainless steel tube concrete short columns, outperforming some existing simplified models. However, the authors acknowledged that the formula was primarily calibrated for short columns and may require modification for slender columns where buckling becomes the governing failure mode. Engineers applying this formula should verify its applicability for their specific column slenderness ratios and boundary conditions.

Engineering Practice and Design Implications

For engineers designing stainless steel tube concrete structures, this study provides several actionable insights. First, the width-to-thickness ratio should be carefully controlled to ensure adequate local buckling resistance, with values below 25 generally providing good performance. Second, the constraint effect of the stainless steel tube is a powerful mechanism for enhancing concrete strength, and this effect should be explicitly considered in design calculations. Third, the use of chamfered corners can improve ductility without significantly compromising strength, making it a practical design option for seismic applications.

The corrosion resistance of stainless steel makes these composite columns particularly suitable for aggressive environments such as marine structures, chemical plants, and bridges exposed to de-icing salts. The long-term durability of stainless steel tube concrete columns is expected to be significantly superior to conventional carbon steel tube concrete columns, potentially reducing lifecycle maintenance costs despite higher initial material costs. This sustainability advantage is increasingly important in modern infrastructure projects that prioritize lifecycle assessment and carbon footprint reduction.

The study contributes to the growing body of knowledge on stainless steel composite structures and provides a foundation for future research on long-term behavior, cyclic loading performance, and fire resistance of square hollow stainless steel tube concrete columns.