Behaviour of CFDST chord to CHS brace composite K-joints: Experiments

Concrete filled double-skin steel tubular (CFDST) members have a large potential to be used in trusses, bridges and lattice structures. Previous research work has focused on the structural performance of individual CFDST components whilst there is a lack of understanding on the behaviour of typical connections formed by such composite members. This paper intends to fill the knowledge gap in this area. A total of 20 K-joints with circular CFDST chords and circular hollow section (CHS) braces were tested under two typical sets of boundary conditions. Effects of important parameters were investigated based on the test results, including brace to chord diameter ratio (β), chord hollow ratio (χ) and preloads on the chord. Typical failure modes and load-deformation relations were investigated, in-depth study on the interactions between materials and the load-transfer mechanism were conducted, simplified strength-prediction method for this new type of composite joints was also proposed.