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The factored axial force, Pu, in each of the columns is calculated from the program for each load combination. For each design load combination, the moment capacity of each column under the unfilence of axial load is then determined separately for the major and minor directions of the column, using the three-dimensional interaction failure surface.
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The Mn values used in the calculation of ΣMnc and ΣMnb values are the nominal flexural strengths described in the Flexural Strength and Axial strength or Combined Flexural and Axial Strength titles. Nominal flexural strength Mn, is calculated without using the strength reduction factor (ϕ=1) and as the reinforcement yield stress fy. Mn is shown by the green curve in the graph above.
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