To investigate the mechanical behavior and load-carrying capacity calculation methods of square concrete-filled steel tube (SCFST) members under biaxial eccentric tension, an experimental program was designed and conducted involving three square hollow steel tube members and six SCFST members subjected to biaxial eccentric tensile loading. The key parameters considered in this study include concrete strength, eccentricity, and eccentric angle. The failure processes and modes of the members were carefully observed and documented. Based on the experimental measurements, the load–displacement curves, load–strain curves, and moment–rotation curves were obtained for all tested members. The test results demonstrated that SCFST members exhibited superior mechanical performance under biaxial eccentric tension. Although the concrete in the tensile zone did not directly bear external loads after cracking, the interaction between concrete and steel tube significantly enhanced both the load-carrying capacity and stiffness of the members. The eccentricity had a pronounced influence on the ultimate tensile strength of the members, with increasing eccentricity leading to reduced bearing capacity. The concrete strength showed limited effect on the ultimate eccentric tensile strength. Based on experimental data and theoretical analysis, this study proposed a method for calculating the ultimate load-carrying capacity of SCFST members under biaxial eccentric tension. Using the stress equilibrium approach, the cross-sectional stress distribution was simplified as a biaxial rectangular pattern, and a calculation formula for the eccentric bearing capacity of the members was established. Comparison between calculated and experimental values demonstrated that the proposed method could predict the ultimate bearing capacity of the members with reasonable accuracy.
Mu et al. (Sat,) studied this question.