Slenderness Criterion

λ < λ_{\lim}

λ_{\lim} = \frac{20 \cdot A \cdot B \cdot C}{\sqrt{n}} according to French NA

A = \frac{1}{1 + 0.2 \cdot φ_{ef}} = 0.7 if φ_{ef} is unknown

B = \sqrt{1 + 2 \cdot ω} = 1.1 if ω is unknown

C = 1.7 - r_{m} = 0.7 if r_{m} is unknown

n = \frac{N_{Ed}}{A_{C} \cdot f_{cd}}

r_{m} = \{\begin{cases} 1, if unbraced elements in general \\ 1, if braced elements with moments of first order principally due to imperfections or transversal loads \\ \frac{M_{01}}{M_{02}} \leq 1, if other cases \end{cases}

λ	slenderness criterion
λ_lim	limiting slenderness
φ_ef	effective creep coefficient
ω	mechanical reinforcement ratio
r_m	moment ratio
M₀₁, M₀₂	algebraic values of first order moments at both ends of element

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