Estudo comparativo entre os resultados obtidos pelo software Ansys Mechanical e a NBR 8800:2008 para a flambagem lateral com torção de vigas metálicas submetidas a carga uniformemente distribuída

In order to study the lateral torsional buckling (LTB) in steel beams, a comparative study was carried out between the calculation method proposed by ABNT NBR 8800:2008 (analytical) and the Finite Element Method using ANSYS Mechanical software (numerical). LTB is an ultimate limit state that occurs due to lateral translation combined with torsion, which can result in structure collapse. In the study, double symmetrical I-profile steel beams with non-slender web were used, with free warping and restrained twist in the both ends, flanges free to move laterally and uniform distributed load along the entire length, applied to the upper flange (destabilizer), bottom flange (stabilizer) and at half height of the cross-section. The analytical procedure considers that the web of the profile is rigid even after the initial deformation, on the other hand, the numerical methods portray in a more realistic way the distortion that occurs in the web during lateral torsional buckling. In addition, ABNT NBR 8800:2008 takes into account only free warping and restrained twist in the both ends and load applied at the semi-height of the profiles. The focus of the analysis was on the variation of the length and the web slenderness, in addition to stabilizing and destabilizing loads. It was concluded that the distortion not considered by the standard directly influences the elastic critical moment. This, in turn, increases with decreasing length and with increasing of the web slenderness. Many of the results obtained are worrisome and can lead to situations contrary to safety, while in others, the distortion effect was negligible on the elastic critical moment and can be neglected.