Examination of the Behavior of Double Cold-Formed Steel Columns with Σ-Shaped Sections Subjected to Non-Uniform Temperature Conditions

Cold-formed steel (CFS) members are widely used in the construction industry due to their versatility, excellent strength-to-weight ratio, and ease of assembly. This paper presents a comprehensive numerical study on the fire resistance of double cold-formed steel columns with Σ-shaped sections under non-uniform temperature distribution. Sheathing CFS members typically exposes the column to fire on one side, and the non-uniform temperature distribution within the column significantly affects its structural response at elevated temperatures. Three types of temperature distribution were considered: ISO uniform distribution, uniform distribution applying the average temperature from thermal analysis, and non-uniform distribution applying different temperatures to the hot and cold flanges. A finite element model of the cold-formed steel column was developed using ABAQUS software. Both structural and thermal analyses were conducted, accounting for material and geometric nonlinearities. To validate the finite element model, the numerical thermal and structural results were compared with previous tests and numerical data. A parametric study was carried out by varying the slenderness ratio, screw spacing, temperature distribution, and load ratio of the member. The results showed that increases in column slenderness and temperature distribution significantly impacted the column's failure time and critical temperature. However, increasing screw spacing did not affect the column's failure time.