Force Redistribution and Bolt-Row Activation in Inclined Extended End-Plate Beam-to-Beam Joints

Inclined extended end-plate beam-to-beam connections are commonly used as kink joints in steel polygonal portal frames, yet their mechanical behaviour is not fully represented by the assumptions of the Eurocode 3 component method. This study investigates the influence of member inclination on stress redistribution within the end plate and the resulting bolt-row activation under bending. Predictions obtained using the Eurocode 3 component method are compared with nonlinear component-based finite-element analyses (CBFEM), and a parametric study is conducted to evaluate the effects of transverse bolt spacing and bolt-row arrangement on moment resistance and force distribution. The results show that member inclination induces a moment-dependent redistribution of tensile and compressive stresses within the end plate, enlarging the tensile region and activating additional bolt rows beyond those considered in the conventional component method. Consequently, tensile forces are redistributed among a greater number of bolt rows, leading to differences between analytical and numerical predictions of the resisting mechanism. The analyses also show that transverse bolt spacing influences not only local T-stub behaviour but also the global redistribution capacity of the end plate. Furthermore, conventional three-row layouts exhibit a distributed 2+2+1 resisting mechanism while maintaining bending resistance within approximately 4% of the reference configuration. These findings provide a mechanical interpretation of bolt-row activation in inclined joints and contribute to improving the understanding of the limitations of simplified analytical design approaches.