Further analysis on mechanical behaviors of blind-bolted T-stub connections to CFDST columns

The mechanical behavior of blind-bolted T-stub connections between concrete-filled double steel tubular (CFDST) columns and steel beams was investigated by cyclic loading tests and numerical simulations. Five bolted joints were tested to evaluate the bending moment (M)-rotation (theta) hysteretic behavior, and the numerical results agreed well with experimental data including the failure mode, initial stiffness, and bending resistance. Results proved that T-stubs with different stiffeners deformed in three modes; the internal force-transferring behavior of blind-bolted joints was different from that of the through-bolted joint, especially the stress response of inner tubes; blind-bolted joints hold a similar bending resistance as the through-bolted joint, but the ductility and energy dissipation capacity were improved significantly. The bending resistance of blind-bolted T-stub connections was predicted based on the tensile T-stub model, and the accuracy of the proposed formula was verified in comparison to both test and numerical results since all the calculation errors were within 9.3%. Parametric study showed that installing stiffeners on the T-stub was the most effective way to enhance the bending resistance, the effect of thickening the T-stub flange ranked second, and the growth rate of ultimate bearing capacity slowed down with the bending stiffness increase of the T-stub. Lastly, the optimum strength matching range of the T-stub flange was suggested.