Numerical analysis and punching shear fracture based design of longitudinal plate to concrete-filled CHS connections

The mechanical behaviour of longitudinal plate-to-concrete-filled circular hollow section (CHS) connections under axial tension, eccentric tension and in-plane bending is extensively studied by the experimentally validated finite element analysis (FEA) in this paper. A total of 336 connections with a wide range of parameters on geometrical configurations, material properties and load positions was conducted to investigate (a) the general applicability of the experimental conclusion for the governing limit state, (b) the shear stress profile on the failure face and (c) the design equations based on fracture analytical models under various loading conditions. FEA extended the validity of experimental conclusion that the only governing limit state was punching shear failure instead of the deformation limit of 3% chord diameter (D). With an aim of proposing design equations based on ductile fracture mechanics, the stress distributions on the fracture failure face and the inner concrete were investigated by the parametric study, and then were adopted in the analytical models. Finally, design equations based on semi-theoretical models for the ultimate strength of longitudinal plate-to-concrete-filled CHS connections under three investigated loads were proposed. It is found the connection-capacity predictions agreed with both test and FEA results well.