Axial compressive performance of thin-walled T-shaped concrete-filled steel tubular stub with angle stiffeners

To address the issues of local buckling of the steel tube and insufficient confinement of the core concrete in T-shaped concrete-filled steel tubular (CFST) stub under axial compression, a new stiffening form using angle steel stiffeners was proposed. The stiffeners transform the confinement mechanism in the reentrant corner region from an ineffective passive state to a more effective rigid stiffening system, thereby improving the confinement and enabling reliable prediction of the capacity gain. Axial compression tests were conducted on 16 T-shaped CFST stub, and ABAQUS finite element models were validated and used for parametric analysis. Furthermore, a capacity calculation method incorporating the angle steel stiffeners’ contribution was proposed based on Mander's confined concrete theory. Test results show that setting angle steel stiffeners effectively restricts local buckling in the reentrant corners, enhances the confinement, and changes the concrete failure mode from shear failure to localized crushing. After stiffening, the bearing capacity of the specimens increased by up to 18.3%, and the ductility by up to 19.9%. The finite element parametric analysis showed that smaller angle steel spacing, higher steel strength, higher concrete strength, and thicker tubes improve performance, while angle steel and vertical rib size, and vertical rib angle have a limited effect. In addition, the calculation formula proposed in this study agrees well with test and finite element results. Considering both economy and mechanical performance, it is recommended to prioritize the combined stiffening form of angle steel and vertical rib, with an angle steel spacing not exceeding 200 mm in practical engineering.