Out-of-plane behaviour and FE modelling of a T-joint connection of thin-walled square tubes

Square hollow tubes with T-joint connections subjected to out-of-plane loading conditions are examined numerically. Finite element analysis (FEA) using 2D shell and 3D solid elements of relatively high density are used to determine the stresses in the joint and the joint's stiffness. The parameters describing the joint's stress concentration and the bending stiffness reduction are defined in terms of the thin-wall ratio (the ratio of side length to thickness of the tubes' cross-section) and the length of the longitudinal member and the geometric asymmetry of the T-joint connection. These parameters permit modelling accurately the tubes and the T-connection by simple one dimensional beam elements with certain modifications. The FEA of beam elements are significantly easier to prepare and analyze. To illustrate the correctness of the approach, a structure with a T-connection and dimensions typical for the agricultural industry is considered. It is shown that the modified beam models provide accurately all important information of the structural analysis (i.e. the stresses, displacements, reaction forces, and the natural frequencies) at substantially reduced computational effort in comparison with the complicated FE models built of shell or solid elements. This can be considered the main contribution of this research paper. Using a simplified FE analysis for design has always been attractive to practicing engineers.

► T-joint square hollow tubes subjected to out-of-plane loading are examined.
► FEA using shell and solid elements are used to determine the stresses in the joint.
► Parameters describing joint stress concentration and stiffness reduction are defined.
► These parameters model the tubes and the T-joint by simple 1D beam elements.
► Modified beam models can be used for structural analysis at lower computational cost.