Design resistance of longitudinal gusset-tube K-joints with 1/4 annular plates in transmission towers

In this paper, the design resistance of longitudinal gusset-tube K-joints stiffened with 1/4 annular plates was studied. Full-scale experiments of the K-joints were carried out. The branch loads of the K-joints were equivalent to a vertical shear force (Pv) and a bending moment (Mw). Substantial parametric studies revealed that annular plates had little impact on the ultimate shear force capacity (Pv,u). Nevertheless, they could significantly improve the ultimate moment capacity (Mw,u) and restrain the chord wall deformation. Moreover, the ultimate moment capacity of K-joints reinforced with annular plates was about 1.3–2.3 times that of K-joints without annular plates. The minimum construction dimensions for annular plates were set to R/d0=0.25 and tr/t0=0.75. •Design resistance and failure modes of K-joints with annular plates were investigated.•Full-scale experiments of K-joints were achieved.•Ultimate strength equations for K-joints were proposed.•Difference and relationship between K-joints with and without annular plates were compared.