Steel material properties: Density of steel is 7850kg/m3 and the Young Modulus (E) is 210,000N/mm2. Steel with a nominal yield strength of 275N/mm2 and 355N/mm2 are typically used. Element yield strength reduces as section max thickness increases.
Buckling is the failure mode for a column. First, evaluate the axial and bending applied to the column. Bending moment is taken as the axial load applied 100mm from the outer face of the flange. This is then distributed above and below the floor. This is based on the section stiffness between the two floors calculated as EI/L. If the ratio is less then 1.5 they are evenly distributed. The resistance of the column is based on the likelihood of buckling, as that is the mode of failure for columns. Clause 6.3.1.3 in BS EN 1993-1-1 explains this is calculated as non-dimensional slenderness of the columns. Typically, minor axis will produce the worst reduction factor. For rolled steel sections this is done by using eq 6.50. Reduction factor can be read through a graph, which is applied to the buckling resistance.
Bending moment resistance of steel columns is the same as that derived for a beam section. Reduction factor from lateral torsional buckling is considered in the resistance.
Slenderness is the lateral-torsional buckling factor. This can be conservatively assumed to be 0.9 buckling factor