Concentric and eccentric tensile behaviour of innovative CFST and CECFST column-to-column connections

Steel-concrete composite columns have been widely used in building and bridge structures due to their high strength, high stiffness, and efficient material utilisation. Among them, concrete-filled steel tube (CFST) columns and concrete-encased concrete-filled steel tube (CECFST) columns have attracted increasing attention because of their favourable structural performance. With the growing adoption of precast construction, reliable connection systems for such composite systems have become essential. In this study, the eccentric tensile behaviour of precast CFST and CECFST column connections was investigated through finite element (FE) simulations. The FE modelling approach for precast connections was first described and validated against available test results for precast CFST and CECFST column connections subjected to direct tension. Based on the validated models, a comprehensive parametric study was conducted to examine the effects of eccentric distance, material strength, and the diameter of lapped reinforcing bars on the structural response of the connections under eccentric tension. The influences of key design parameters on stiffness, load-carrying capacity, and failure behaviour were clarified for both connection types. On this basis, practical design recommendations were provided for precast CFST and CECFST column connections subjected to eccentric tension.