Compression performance of cross-shaped CFST columns under concentric and eccentric loading

A cross-shaped concrete-filled steel tube (CS-CFST) is an important component that can be used as a central column in multi-story buildings, as it enhances spatial arrangement and increases the efficiency of indoor space utilization. However, the working mechanism of CS-CFST columns under eccentric loading remains unclear, even though they are often subjected to this loading condition. This article presents an experimental and numerical evaluation of the structural performance of CS-CFST columns, fabricated by assembling two steel parts into a cross-shaped section. The new fabrication scheme is easy, requires minimal welding, and thereby simplifies the pouring process of concrete, which is more beneficial for multi-story structures. Six CS-CFST specimens were tested to investigate the failure modes, peak capacity and ductility under concentric and eccentric loading. The primary test parameters were height-to-width ratio and load eccentricity. The results showed that the compressive strength of CS-CFST columns decreased with the increase of these parameters, while ductility was improved. A finite element (FE) model was proposed and verified using the experimental data, effectively simulating the concentric and eccentric behavior of CS-CFST columns. The parametric study was performed considering the impact of the section width-to-thickness ratio, concrete and steel strength, loading angle and slenderness ratio on the axial load-bending moment relationships and corresponding normalized curves. Based on the design codes and FE analysis, simplified formulas were proposed to reliably predict the axial and eccentric compressive strengths of CS-CFST columns.