Experimental study discussion of the seismic behavior on new types of internal/external stiffeners in rigid beam-to-CFST/HSS column connections

The use of box columns has been increased due to the rigidity of rigid orthogonal moment resisting frames. On the other hand, the installation and welding of necessary horizontal continuity plates inside the columns are both labor-consuming and costly tasks. In this paper, an experimental study of the seismic behavior of internal/external stiffeners in rigid beam-to-Concrete Filled Steel Tube (CFST) and Hollow Steel Section (HSS) column connections is presented respectively. In this study, four hollow steel section specimens and six concrete filled steel tube section specimens are investigated. The results show that specimens with external stiffener in both cases (HSS and CFT) provide seismic parameters and they move the plastic hinge away from the column face due to their specific geometry. Therefore external stiffeners proposed in this study can be a good alternative for connections with continuity plates (suggested connection of design codes).