Flexural behavior of aluminum alloy hub joints and simplified spatial beam-element modeling method

To investigate the flexural behavior of aluminum alloy hub joints in spatial grid structures, four groups of bending tests were designed. Comparative analyses of flexural behavior under different loading directions were conducted, and a refined finite element model for out-of-plane bending was developed using ABAQUS to elucidate mechanical mechanisms. Meanwhile, a parametric analysis was carried out to examine the effects of wedge rate w, tube diameter D_c, and wall thickness t on out-of-plane flexural behavior. Results indicate: (1) The joint exhibits semi-rigid behavior in out-of-plane bending, while its in-plane bending can be treated as pinned; (2) The failure mode of in-plane bending manifests as buckling at the interface between insertion part and transition part, whereas out-of-plane bending induces three failure modes: transition part buckling, insertion part tensile fracture, and rib shear failure; (3) The failure process of out-of-plane bending sequentially comprises: elastic load-bearing stage of ribs, elastoplastic load-bearing stage of ribs, and primary load-bearing stage of transition part; (4) Reducing w while increasing D_c and t enhances out-of-plane flexural behavior. The stiffness sensitivity coefficient ξ_Ko of D_c is 6.21 times that of t, the bearing capacity sensitivity coefficient ξ_Muo is 1.58 times that of t and 16.59 times that of w, and the rotation sensitivity coefficient ξ_φuo of D_c and t is 4.69 times that of w. Enhancing out-of-plane flexural performance should prioritize increasing D_c, supplemented by increasing t. Furthermore, accounting for the influence of the nonlinear transition part on member deformation, a method is established for enhanced simplified beam-element modeling using spring elements with length L_c, and deriving the L_c calculation formula. These results can serve as a basis for the design and implementation of aluminum alloy hub joints.