Study on spatial effect of concrete-filled steel tubular KK-joints

In order to find out the spatial effect of multi-planar concrete-filled steel tubular (CFST) joints, the mechanical behavior of multi-planar CFST joints was studied through refined finite element simulation. Accurate finite element models of CFST KK-joints were established by considering the material nonlinearity, geometrical nonlinearity, and contact nonlinearity between the tube and the concrete. The influence of spatial effect on the capacity and failure mode of the joint was studied. The results show that, the capacity of multi-planar CFST joints is much higher than that of the steel tubular joints. The failure mode of the multi-planar CFST joints is the same as the failure mode of planar CFST joints. There are two failure modes of the joints, one is the combined failure of chord punching shear and brace yield, and the other one is the chord punching shear. The spatial effect has different influences on the capacity of steel tubular joints and CFST joints. The capacity of the multi-planar CFST joints with angle 60°of the braces is lower than that of planar CFST joints, and the effect of spatial effect should be considered in design. The spatial effect has little effect on the stiffness of the multi-planar CFST joints.