Calculation Method for the Critical Temperature of Bending and Torsional Buckling of the herringbone steel frame columns in Substations Under Fire Conditions*

Abstract The weak position of the frame columns is determined by analyzing the structural form and working characteristics of the herringbone steel frame columns (HSFC) in substation. Based on the equilibrium method, the formula for calculating the bending and torsional buckling load of the HSFC at ambient temperature has been derived. Then, the critical temperature of the bending and torsional buckling of the HSFC under fire conditions can be developed, by incorporating the effect of high temperature on the modulus of elasticity of steel. Five fire tests on the HSFCs were conducted to determine the critical temperatures of the bending and torsional buckling of the HSFC under different load ratios, and the test results verified the validity of the proposed method.