Behaviour and design of restrained steel column in fire, Part 3: Practical design method

This paper presents a practical design method for calculating the buckling and failure temperatures of restrained steel column under axial load or combined axial load and bending moment based on the results of extensive numerical parametric studies. Design equations for unrestrained columns in fire are adopted to calculate the buckling temperature of a restrained column by including the additional compression axial force due to restraint thermal elongation. The cross-section yield axial strength–plastic bending moment interaction curve is employed when calculating the failure temperature of restrained column. Results from the proposed method are compared with ABAQUS simulation for different cases. For the restrained column under axial load only, the buckling and failure temperatures calculated by the simplified method agree well with predictions by ABAQUS. For the restrained column under combined axial force and bending moment with realistic parameters, the buckling and failure temperatures predicted by the proposed method also agree well with ABAQUS predictions.