Structural testing and numerical modelling of T-joints between cold-formed S690 circular hollow sections under brace in-plane bending

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• Six T-joints between S690 CFCHS were tested under brace in-plane bending. • Both monotonic and cyclic actions were applied to these joints. • All joints failed with a fracture in the heat-affected zones of the braces. • An integrated numerical modelling approach was developed to examine these joints. • Heat transfer, thermomechanical and structural analyses were performed. • Residual stresses caused little strength reductions in these T-joints. This paper presents a comprehensive investigation into the structural behaviour of T-joints between high strength S690 cold-formed circular hollow sections (CFCHS) under brace in-plane bending, and deformation characteristics of these T-joints under both monotonic and cyclic actions are examined experimentally and simulated numerically. These T-joints between S690 CFCHS were found to deform with a high level of resistances and ductility under both monotonic and cyclic actions. Through an integrated numerical modelling approach developed by the authors, advanced three-dimensional finite element models of CFCHS with solid elements were established. With a proper definition of weld collars at the brace/chord junctions of the T-joints between S690 CFCHS with different diameters and thicknesses, these models were readily adopted to perform a heat transfer analysis, a thermomechanical analysis and a structural analysis sequentially with compatible element types and meshes. Hence, the effects of the welding-induced residual stresses at the welded brace/chord junctions onto the structural behaviour of these T-joints were readily assessed. Consequently, these advanced models are demonstrated to be able to predict rationally deformation characteristics of these T-joints between S690 CFCHS under monotonic and cyclic actions of brace in-plane bending with a high degree of structural accuracy.