Numerical evaluation on shear behavior of irregular steel beam-to-CFST column connections

The unequal-depth steel beam to concrete-filled steel tubular (CFST) column connection with outer annular stiffener is an efficient seismic resisting system for unequal-span building structures. Numerical analyses were performed to investigate the elasto-plastic behavior and local responses of the panel zone in beam-to-CFST column connections. Three dimensional nonlinear finite element model was developed and verified by comparing with the experimental results. Parametric studies were conducted to investigate the effects of influential parameters on shear capacity of panel zones. Results showed that the beam depth ratio (Db2/Db1) played major impacts on the failure modes of the unequal-depth panel zones. The primary panel, the outer annular stiffener, the tubular column flange and the in-filled concrete contributed to the shear strength of the whole panel. In contrast, the secondary panel demonstrated minor effect on the shear strength of the whole panel and could be ignored in structural design. The beam depth ratio (Db1/Db2) and width-to-thickness ratio of the steel tube (D/t) were the main parameters that control the yield and ultimate shear strengths of the entire panel.