Cyclic Response and Energy Dissipation of Angle-Reinforced Screw Connected Cold-Formed Steel Frames

The cyclic performance of cold-formed steel frames depends strongly on the behavior of their beam-column connections, particularly under repeated lateral loading. This study examines whether adding top and seat angles to an inner-plate connection can improve the response of back-to-back cold-formed steel frames. Four frame specimens were tested under reversed quasi-static loading. Two specimens were reinforced with inner plates and top and seat angles, while the other two were reinforced only with inner plates. Load resistance, ultimate displacement, displacement ductility, secant stiffness, energy dissipation, and deformation patterns were evaluated. The angle-reinforced frames reached 13.83 kN in both loading directions and sustained larger displacements than the frames without angle reinforcement. A clear difference was found in energy dissipation. The reinforced frames dissipated an average of 62.31 kJ, compared with 18.07 kJ for the unreinforced frames. Even when only the loading phases completed by all specimens were considered, the reinforced frames dissipated nearly twice as much energy. In contrast, the differences in displacement ductility and secant stiffness were relatively small. Visual observations also revealed distinct deformation patterns: the reinforced specimens exhibited localized deformation at the angle plates, whereas the unreinforced specimens showed more pronounced member distortion and screw tilting. Overall, the top and seat angles primarily improved the connection's ability to maintain resistance, accommodate deformation, and dissipate energy under repeated loading.