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 (P-v) and a bending moment (M-w). Substantial parametric studies revealed that annular plates had little impact on the ultimate shear force capacity (P-v,P-u). Nevertheless, they could significantly improve the ultimate moment capacity (M-w,M-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/d(0) = 0.25 and t(r)/t(0) = 0.75.