Rigidity estimation of embedded CFST column-to-beam connections

This paper presents a finite element analysis (FEA) of embedded concrete-filled steel tube (CFST) column-to-beam connections subjected to combined axial-flexural loading. The proposed FEA model was verified by experimental results from previous research. The comparison and analysis show that the predicted local damages, failure patterns, and load versus displacement curves were generally in good agreement with the experimental observations. Several identified parameters were studied, including various concrete strengths, steel tube yield stresses, embedded lengths, and axial loading ratios. Based on the parametric study, provisions and methods to estimate the effective flexural stiffness of the composite columns were suggested, and simple equations to estimate the effective stiffness of the whole connection were proposed. In addition, the fracture strain captured in the cyclic loading test was greater than that captured in the uniaxial tensile test. The inelastic responses of the CFST connections can be recorded using the FEA models, and the longitudinal strain can be used to define when tube tearing will occur, while the plastic equivalent strain can be used to define where tube tearing will occur.