Experimental study and numerical evaluation of an innovative connection with Tubular Flange Beam

Common RBS connections, characterized by radial cutting in the flange, suffer from reduced flexural capacity and lateral-torsional buckling. To address these drawbacks, a new connection called Tubular Flange Beam (TFB) is proposed. In the TFB connection, a portion of the beam’s flanges and web is replaced by tubes at the expected plastic hinge location. In this research, seismic behavior of the TFB specimen is studied experimentally and evaluated numerically under cyclic loading. The study is focused on failure modes, hysteretic behavior, and energy dissipation capabilities. Moreover, some geometrical and mechanical parameters of the TFB connection such as diameter, thickness and strength of the tube are evaluated. In addition, the seismic behavior of the TFB connection is compared against the traditional pre-Northridge fully-welded beam-to-column (FWBC) connection’s behavior and the conventional RBS connection. Results indicated that the TFB connection effectively concentrates plastic strains within the reduced region, resulting in a notable decrease in strain demands near critical welds. Moreover, the connection exhibited sufficient energy dissipation and stable hysteresis behavior, with no strength degradation observed up to a 7% story drift ratio. Additionally, parametric studies showed that changes in tube thickness have the greatest effect on the seismic behavior of the TFB connection. Furthermore, unlike the RBS and FWBC connections, the TFB connection behaved more stable during higher rotations and had not experienced strength degradation during high rotations.