ABSTRACT
The deformation capacity and ultimate load capacity of K-joints fabricated from cold-formed rectangular hollow sections at − 40°C has been studied both experimentally and numerically. The predicted load-deformation behaviour of a K-joint based on non-linear finite element analysis compared well with the experimentally measured behaviour. Such analysis, however, was not able to provide information on the ultimate strength or ultimate deformation capacity of a joint. An extensive experimental program on welded K-joints at low temperatures revealed that the primary failure mode was ductile tearing of the chord flange at the weld toe of the tension brace flange. For this reason it was hypothesized that J-integral evaluation of an advancing crack could be combined with measured materials data to assess the ultimate strength of a joint. J-Δa material testing was performed at − 40°C on material taken from the wall of a welded structural hollow section. This data has been combined with detailed FE-based J-integral analysis of a crack growing from the weld toe. This assessment revealed that crack advance, once initiated, would be expected to continue through the wall thickness of the chord member with very little change in load. This ductile fracture assessment method was found to be effective in modelling the ultimate ductility of the joint.
