Experimental seismic behavior of through-diaphragm connections to concrete-filled rectangular steel tubular columns

In this paper, four full-scale specimens of existing and proposed through-diaphragm connections to concrete-filled rectangular steel tubular columns were tested under cyclic lateral load. The variables in the experiments include the geometry of the through-diaphragm, the configuration of the weld access hole, horizontal stiffeners, and the methods of connecting beam webs to columns. Three failure modes were observed in the test. The strength, stiffness, ductility and energy dissipation capacity were evaluated at different load cycles. It is found that the moment-rotation hysteresis curves are all stable and plentiful and exhibit no obvious strength deterioration or stiffness degradation. The energy dissipation capacity of the proposed through-diaphragm connections are significantly improved when compared to the existing one. Although fabricated in poor condition with an extremely low temperature, the proposed connections could obtain more than 0.1 rad of the inelastic rotation capacity. This indicates that the proposed through-diaphragm connections show good seismic behavior and could be applied to composite ordinary moment frames.