Seismic behavior of cold-formed steel frames with bolted moment connections

This study investigates the behavior of cold-formed steel (CFS) structural members under seismic loading using specially designed screwed moment connections through experimental methods. Within the scope of the research, T-shaped frame systems composed of CFS columns and beams with varying cross-sectional properties and material thicknesses were prepared, and quasi-static cyclic loading tests in accordance with FEMA-350 standards were applied to these systems. In the experiments, the effects of the screwed connection details used at the joints on system stiffness, load-bearing capacity, rotational performance, and energy dissipation capacity were analyzed. In all specimens, beam webs were manufactured without openings, and five different configurations with varying gusset plate thicknesses were tested. Experimental findings revealed that the application of smart screws provides higher shear and tensile strength compared to conventional screws. Studies have shown that smart screw applications increase shear and tensile strength by approximately 20% to 40% compared to traditional screws. Additionally, comparison of design and application parameters indicated that smart screws enhance moment capacity in the connection regions by approximately 30% . Moreover, the ductility ratio, which is of critical importance under seismic effects, was found to increase by approximately 30% as well. Furthermore, it was observed that this connection method has positive effects in maintaining structural performance under repeated seismic loads. The obtained moment-rotation relationships and deformation data confirm that these connection systems provide a safe, economical, and applicable solution in earthquake-resistant structural design. This study makes a significant contribution to the development of innovative connection techniques aimed at improving the seismic performance of cold-formed steel structures.