Degrees of bending (DoBs) in bulge formed K-joints under balanced axial loads

The bulge formed joint, an innovative joint with a bulge plate employed for the connection between the braces and the chord, was firstly put forward by authors. However, the degrees of bending (DoBs) of the joint which are important to the accurate prediction of the fatigue life using the fracture mechanics method are unclear so far. In this paper, the finite element (FE) method verified by experimental data was utilized to investigate the DoBs of the bulge formed K-joints under balanced axial loads. Then the geometrical effects on the DoBs at key locations (the crown position and φ = 105° position which is nearby the saddle position) were investigated by 2117 FE models. The geometrical parameters of the bulge formed K-joint investigated in this study include τs, η1, η2, θ, β, γ, τ, of which the first three parameters are typical for the bulge formed joint and the other four are same as those in the unstiffened joint. By large amounts of nonlinear regression analyses, a set of parametric formulas were derived for the DoBs.