Seismic behaviour of innovative ring-bar reinforced connections composed of T-shaped CFST columns and RC beams with slabs

An extensive set of experimental programme on the behaviour of innovative ring-bar reinforced connections composed of T-shaped concrete-filled steel tubular (CFST) columns and reinforced concrete (RC) beams with slabs are reported in this study. Specifically, for the proposed connection, the T-shaped CFST column is welded with an H-shaped steel corbel, which is embedded into the reinforced concrete beam and slab. Moreover, a few ring-bars are fabricated to improve the seismic resistance capacity of this connection. A total of six specimens are tested: one specimen is tested under monotonic loading to investigate the load-displacement relationship and the development of strains; and the other five specimens are tested under cyclic loading to obtain the seismic behaviour of these specimens. The test results demonstrate that the seismic behaviour of the proposed connections is prominent and that the diameter and number of ring-bar and length of steel corbel are found to be significant factors of the seismic behaviour of the connections. Complementary to the experiments, a finite element (FE) model is developed to further analyse the experimental results by illustrating the failure modes of the specimens and extending the parametric studies which are not studied through the limited experiments. The comparison between the FE analysis and the experimental results demonstrates the accuracy of the proposed model. Numerical results indicate that the ring-bar and slab are able to increase the stiffness and bearing capacity of the specimens; the reinforcement ratio of beam, the concrete strength of the beam and slab play important roles in improving the ultimate strength of the specimens.