Abstract: Abstract: In order to study the fire resistance of double-C-shaped cold-formed steel split section column, the temperature field distribution and fire resistance rating of double C-shaped cold-formed steel split section column under fire were numerically analyzed by finite element software ABAQUS, and the numerical analysis results were verified by experiment. Considering the influence of axial compression ratio and length and slenderness ratio, the critical temperature of steel column was analyzed, and the influence of fire resistant gypsum board thickness on the fire resistance rating of steel column was investigated, and the analysis results showed that the critical temperature of steel column decreased significantly with the increase of axial pressure ratio. The influence of the length and slenderness ratio on the critical temperature of the steel column is relatively small. The use of fire resistant gypsum board to protect the steel column can effectively improve the fire resistance rating of the steel column. Regression analysis was carried out on the critical temperature data of different axial compression ratios and length and slenderness ratios, and a simplified calculation formula for critical temperature of double-C-shaped cold-formed steel flattened cross-sectional columns was obtained. In addition, the temperature calculation formula of the steel column was obtained by fitting the heating curve of the fire resistant gypsum board protection steel column, and the calculation formula of the fire resistance rating of the fire resistant gypsum board protection steel column was derived, which provided a reference for the fire resistant design of the cold-formed steel column.

Key words: Key words: cold-formed steel, fire resistant gypsum board, fire resistance rating, critical temperature