Section Modulus at Point i About z-Axis

W_{z, i} = \frac{I_{y} \cdot I_{z} - {I_{y z}}^{2}}{I_{y} \cdot y_{i} - I_{y z} \cdot z_{i}}

ρ	Adjusted reduction factor
N_Ed	design value of acting axial force
l	free length
M₀₁, M₀₂	algebraic values of first order moments at both ends of element
M_0Ed	ultimate moment of first order under combination of design loads (including geometric imperfections)

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