Mechanical behaviour of concrete-filled CHS connections subjected to in-plane bending

This paper presents an investigation on the mechanical behaviour of concrete-filled circular hollow section (CHS) connections. Four large-scale connection specimens were tested to failure under in-plane bending. The main test parameters included chord-wall slenderness and diameter ratio between brace and chord. The main failure mode observed from the tests was chord-wall punching shear failure. Meanwhile the chord-wall deformation was also investigated to determine the governing limit state. Complementary finite element (FE) methodology was validated against the experimental findings and the validated FE models were used to further study the mechanical behaviour and the strength design of the connections. The modified Mohr-Coulomb criterion (MMC) was introduced into the finite element models to capture steel fracture failure. Based on both experimental and numerical investigations, a theoretical analytical model with the consideration of the inner concrete was established and an ultimate strength design equation was proposed accordingly to predict the punching shear strength for concrete-filled CHS connections under in-plane bending.