Numerical Investigation on Load-bearing Capacity of K-Joint Concrete-filled Steel Tube under Static Loading

The performance of concrete-filled steel tubular (CFST) composite joints needs to be investigated under different loading types. Thus, the influential parameters should be evaluated with an aim to enhance the load-bearing capacity of structures with these composite members. This study presents a non-linear finite element modeling (FEM) analysis to evaluate the performance of K-jointed CFST joints. Accordingly, a set of 32 joint models were created using ABAQUS and the effects of various mechanical and geometrical parameters were discussed. These parameters involved steel tube thickness, section dimensions, compressive strength of infill concrete, gap and horizontal angle between joint components. Therefore, the load-bearing capacity and the stress-strain variations of K-joints were examined. Based on the results, it was noticed that by increasing the wall thickness of the primary steel tube, the initial stiffness, the ultimate load, and the displacement of the entire K-joint are reduced, but the ductility is increased. Also, as the diameter of the primary member increases, the ductility of the K-joint decreases. Furthermore, increasing the infill concrete compressive strength has a slight effect on the stress and ultimate strain of K-type joints. The failure mechanism of the joints was so that the secondary steel member is subjected to buckling at the connection point, giving rise to deformation and warping of the joint at this point, thus leading to the overall failure of the joint. It was also revealed that increasing the gap between the two secondary members significantly increases joint rigidity and reduces ductility, while it has a slight effect on the stress level of the K-joint. Moreover, the greater the angle between primary and secondary tubes, the higher the load-bearing capacity.