DETERMINATION OF THE CRITICAL LENGTH EQUATION OF DISTORTIONAL BUCKLING

Resumo

The use of cold-formed steel members has grown significantly and for this reason a number
of design codes have been used such as NBR 14762 [1], AISI S100 [2] and AS/NZS 4600 [3]. The
susceptibility of these types of profiles to the phenomena of local, global and distortional instability
mainly has made the design codes to approach this topic in more detail. Nevertheless, the present
methodologies are little simplified or result in high conservatism. Thus, several studies have been carried
out aiming at the presentation of more simplified equations that result in a less conservative way to
represent the real behavior of these profiles. It was observed that the buckling length has relevant
participation in determining buckling mode, however there are many difficulties in determination of the
distortional buckling stress and its associated length. Thus, this paper aims to express a more simplified
equation for the length associated with distortional buckling. So, a selection of profiles with a C-section
with stiffener that complied with the geometric and mechanical specifications of the design codes was
performed. Using software based in Generalized Beam Theory, presented by Silvestre and Camotim [4],
several simulations were made with these profiles. The profiles were analyzed with end support
condition pinned-pinned under centered compression. The results were used to create artificial neural
networks from which were generated equations for the critical length of distortional buckling. The
equations were validated with the results available in the literature, whether experimental or numerical,
and showed good correlations.