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The limit slenderness is calculated according to clause 5.8.3.1(1) in EN 1992-1-1. The limit slenderness and the slenderness are always checked separately for each direction according to 5.8.3.1(2) in EN 1992-1-1. The formula for calculation of limit slenderness in EN 1992-1-1 is national parameter, it means, that different formula, method or value can be used in some countries, see concrete setup (Manager for national annex > EN 1992-1-1 > General > ULS > General > lambda_lim )
There are changes in calculation of limit slenderness for some national annex see the table below
| National annex | Calculation of limit slenderness |
| Standard EN 1992-1-1 | λlim = (20 ∙ A ∙ B ∙ C) / √n |
| DIN EN 1992-1-1 NA |
λlim = 25 ... for |n| ≥ 0,41 λlim = 16 / √n ... for |n| < 0,41 |
|
ČSN EN 1992-1-1 NA STN EN 1992-1-1 NA |
λlim = (20 ∙ A ∙ B ∙ C) / √n ≤ 75 |
For more details about National annexes see "Theoretical background for National annexes".
where
| A | the coefficient based on effective creep ratio φeff, see "Effective creep ratio" |
| B | the coefficient based on mechanical reinforcement ratio ω, see "Mechanical reinforcement ratio - check" or "Mechanical reinforcement ratio - design" |
| C | the coefficient based on shape (ratio) of bending moment rm, see "Shape of bending moment" |
| n | the relative normal force n, see "Relative normal force" |
The limit slenderness is not checked if normal force (relative normal force) is tensile.
The limit slenderness is calculated in each section, it follows that for arbitrary member, member with a haunch, member with non-uniform normal force along the length of the member or member in which the reinforcement is not constant over the length of the member, the limit slenderness can vary along the length of the member.