1. Special features of thin elements

1.1 Definition of this class

Two aspects of behavior lead to the qualification of a structural element as "thin":

• under compression: the element is considered "thin-walled" when, under compression, some of its parts are susceptible to local instability before the elastic limit is reached. Such instabilities include wall buckling, instability due to cross-section distortion (buckling of stiffeners) and local crushing on supports;

• under the effect of torsion: the element is considered "thin-walled" when, under the effect of torsion alone, the normal stresses created by torsion in the section are no longer negligible. This situation arises for a load applied outside the shear center, when each of the three...