Experimental Investigation of the Cold-Formed Steel Beam-to-Column Clip-Angle Screwed Connections at Ambient and Elevated Temperatures

Abstract The present study examines the behavior of beam-to-column cold-formed steel (CFS) clip-angle screwed connections in ambient and elevated-temperature conditions through a total of 49 experimental tests. The aspect ratio of the clip-angle, defined as the width-to-depth ratio, was varied from 0.19 to 0.96 by considering different combinations of clip-angle width, depth, and thickness. Failure modes were systematically classified, and the rotation and deformation characteristics were analyzed using a three-dimensional digital image correlation (3D-DIC) technique. Elevated-temperature tests were conducted by applying 50% of the ambient-temperature load and subsequently exposing the connections to the ISO 834 (International organization for standardization) standard fire curve until failure. These fire tests were conducted in a custom-designed furnace that enabled full-field DIC strain and deformation measurements. Based on the ambient-temperature results, an improved design strength equation is proposed for the investigated clip-angle configuration. The critical temperature of the clip-angle screwed connections was determined because it is a crucial parameter for evaluating the fire resistance and onset of strength degradation in elevated-temperature conditions. In addition, the performance of the present screwed connections was compared with existing studies to highlight differences in strength, deformation, strength degradation and failure behavior.