As far as Code_Aster is concerned what is calculated is a coefficient which is the ratio of the critical load, as seen above, by the applied vari- able load. Variable because Code_Aster allows to make the calculation with a fixed load and a variable load and the coefficient is applied to this second variable load. In the following example the fixed load is only the boundary conditions and no forces, except a commented line which can be un-commented in a second run to see what it does.