Shear capacity of 3D composite CFT joints subjected to symmetric loading condition

• 3D composite joints of CFT column and steel beams subjected to beam loadings in two planes
• Analytic shear capacity model of a 3D composite joint is established.
• Good agreement of shear–deformation relationship and ultimate shear capacities between predicted and experimental results
• Parametric analysis of the ultimate capacities of 3D composite joints

Shear capacity analysis of the panel zone in a composite joint of concrete-filled steel tubular (CFT) column and steel beam is important for avoidance of premature shear failure of the joint. This paper reviews 2D shear capacity models for joints between CFT column and steel beam. Then a 3D model is proposed for consideration of joints subjected to symmetric beam loadings in two planes and compared to the existing 2D shear capacity models. The effects of encased concrete on the shear capacity of the joint are taken into account for 3D composite joints through an additional compression strut model. A shear force and deformation relationship with four linear segments is thus achieved for a composite joint. To evaluate the corresponding ultimate shear capacity, the modeling results are compared with experiments where specimens fail through shear mode at the joints. It is found that the shear–deformation relationship and ultimate shear capacities predicted for 3D composite joints agree well with the experimental results.