Capacity of steel CHS T-Joints strengthened with external stiffeners under axial compression

The capacity of steel circular hollow section (CHS) T-joints reinforced with external stiffeners under axial compression is studied by finite element (FE) modeling and theoretical analysis in this paper. The FE modeling approach is first validated by results from axial compressive experiments on nine T-joints with and without stiffeners. Then 256 T-joint FE models are established and analyzed to investigate the influence of the size of external stiffeners and joint geometry on the improvement of ultimate capacity of the joints under axial compression. The results from parametric analysis show that the increment in ultimate capacity decreased when the diameter ratio between the brace and the chord β increased, whereas it remained almost proportional to the factor of stiffener length to the brace diameter η. In addition, for such T-joints, when the thickness of external stiffener was no less than that of the chord wall, the effect of the factor of stiffener thickness to the chord thickness λ and the diameter to thickness ratio of the chord 2γ on the improvement of ultimate capacity was not obvious. On the basis of the yield line model, a theoretical formula is further derived to predict the ultimate strength enhancement of reinforced T-joints with external stiffeners.