Cold-Formed Steel Beam-to Screw Connections Exposed to High Temperatures Reinforced with CFRP

Abstract

This study uses eight tests to show the experimental behavior of cold-formed steel beam-to-column screw connections exposed to high temperatures reinforced with CFRP. The structural beam members were heated from room temperature to 600 degrees C, held at that temperature for 5 h, and then cooled to room temperature before being reinforced with CFRP (carbon fiber-reinforced polymer). The joint's energy dissipation capacity, moment-rotation behavior, and ductility under high-temperature conditions were investigated using different beam thicknesses, gusset thicknesses, and stiffeners. The results demonstrate that increasing the gusset thickness reduced the moment, stiffness, and rotational values of the connection for beams without stiffeners but increased the beam's ductility. Using stiffeners reduced the beam's ductility but increased its energy dissipation capacity. In addition, increasing the profile thickness decreased the energy dissipation capacity. The collapse modes under high-temperature reinforced with CFRP conditions were compared to ambient temperature and post-fire conditions. The findings show that the buckling of models is affected by the thickness of the beam's wall. When the thickness of the beam wall exceeds the thickness of the gusset plate, collapse mode occurs, resulting in screw breakage. Beam buckling does not appear in beams that have stiffeners at the connection. This means that the beam will not buckle no matter how many stiffeners are employed in the connection. In addition, beam buckling was too common in beams exposed to high temperatures. Furthermore, the use of CFRP in the beam reduced buckling. All connection collapses are induced by the screw when the beam thickness divided by the gusset thickness is less than one; otherwise, they are caused by the gusset yield with screw rupture.