Performance and design of full-width RHS X and T joints under brace axial tension and brace bending

Abstract

Within the research framework for updating the international design standard ISO 14346 for hollow section joints, this study examines brace failure and chord sidewall failure in full-width rectangular hollow section (RHS) X and T joints under brace axial tension, brace in-plane bending and brace out-of-plane bending. The codified design rules for full-width RHS joints are reviewed, with their limitations highlighted. Design resistance equations for brace failure, based on the modified effective width method, and also for chord sidewall failure, using the modified bearing–buckling method and the Lan–Kuhn method, are then proposed. Up-to-date experimental and numerical results are collated from the literature, which cover a wide range of geometrical parameters, steel grades ranging from S235 to S960, varying weld details, and loading cases of brace axial tension, brace in-plane bending and brace out-of-plane bending. The compiled results are adopted to evaluate the performance of full-width RHS joints and to assess suitability of the proposed design resistance equations. It is shown that weld details can significantly affect the deformation capacity and static strengths of full-width RHS joints. The proposed design resistance equations yield conservative and reliable strength predictions for full-width RHS joints. Welding guidance and user-friendly design rules, in which an extension to include Class 3 cross-sections is included, are suggested for full-width RHS X and T joints.