Design of partial height web stiffeners in beam-to-column joints and influence of residual stresses induced by welding

Fixed beam-to-column joints in steel portal frames with bolted connections typically present stiffeners to ensure proper load bearing resistance and stiffness to the joint. Executing the same stiffeners with a reduced height (e.g. partial height web stiffener) allows for cost saving during manufacturing but must be paid off by considering its effects in the design verification of the joint. The usual gap size of the partial stiffener has a height of 10%–30% of the concerned element web depth. Based on the Astron product example, this study analyzes the effects of the partial stiffener on the concerned knee joint resistance components according EN1993-1-8. A numerical parametric study is performed based on an advanced 3D FEM model to determine and compare the structural behavior of the beam-to-column joints with full and partial stiffeners. Comparison of the calculation results prove, the partial stiffener influences only the shear panel resistance component, and it has no effect on other components of the joint. The failure mechanism of the shear panel using different slenderness ratios are analyzed in the paper and an enhanced design method is developed, which allow to consider the geometrical gap between the flange and stiffeners. The effect of residual stresses resulting from the manufacturing processes of the plated elements is also analyzed and introduced in the paper using advanced weld simulation technique.