Static performance of square CFDST chord to steel SHS brace T-joints

Abstract

In this paper, static performance of square concrete-filled double-skin steel tube (CFDST) chord to steel square hollow section (SHS) brace T-joints are investigated through experimental and numerical studies. Twelve specimens, including 8 T-joints with square CFDST chord, 2 T-joints with square concrete-filled steel tube (CFST) chord and 2 T-joints with steel SHS chord as counterparts, were tested under continuously increasing compressive force on the brace with concentric compression load applied simultaneously to the chord. The influence of chord type, brace-to-chord width ratio (β) and concentric compression level of the chord (n) on the static performance of the T-joints was examined. It is found that the composite T-joints have enhanced static performance than their steel counterparts. For the composite T-joints, the failure pattern varies from compression-flexure-shear failure of composite chord to local buckling of steel SHS brace when β reduces. Moreover, while only the composite chord failure occurs, the bearing capacity of the specimens augments with growing of hollow ratio of CFDST chord (χ), β and n; however, when only steel SHS brace of the composite joints fails, the chord type has a moderate influence on the bearing capacity of the specimens. The static performance of the T-joints was simulated using a finite element (FE) model, which is validated against the observations in the experiment. On the basis of the experimental and numerical research, the design formulae for bearing capacity of the composite T-joints were developed, and a good accuracy of the computations was achieved.