Experimental and numerical study on the new transfer joint for CFST to RC column connections in high-rise buildings

New transfer joints that increase usable building space lack specific design methods and have been tested using relatively few specimens. This study proposes a design method for a new transfer joint connecting concrete-filled steel tube columns to reinforced concrete columns. The method uses moment distribution to calculate joint internal forces and determines the location of the maximum stress in the tapered steel tube. Experiments further validate the reliability of the joint. A modelling approach is developed in OpenSees, with a maximum discrepancy of approximately 12% between the simulated and experimental results. Parametric analysis indicates that, for taper slopes gentler than 1:6, the yield point, ultimate load-carrying capacity, and ductility factor vary only marginally. Numerical analyses of high-rise frame structures incorporating the new and conventional transfer joints show differences of approximately 0.5% in natural vibration periods and broadly similar mode shapes. Under seismic excitation with a peak ground acceleration of 0.6 g, the maximum difference in inter-storey displacement at the transfer storey is approximately 1.138 × 10 −4 mm. Varying the number of basement storeys through which the steel tube is embedded has a minimal effect on its stress, with a maximum variation of approximately 0.018 MPa; the steel tube remains elastic. Embedment through one basement storey satisfies the service requirements. The experimental and overall structural analyses demonstrate that the new transfer joint provides performance broadly comparable to that of the conventional joint.