Estudo comparativo dos resultados numéricos da flambagem lateral com torção com os resultados analíticos obtidos pela NBR 8800:2008

The lateral torsional buckling is a limit state characterized by the combination of lateral displacement with twist until it reaches the collapse. Different results of lateral torsional buckling analyses in steel beams of doubly symmetric I-section of simply supported with free warping and restrained twist in the both ends were compared, analytical results obtained from Brazilian standard ABNT NBR 8800:2008, and numerical results, whose software ANSYS was pioneer in your application from Finite Element Method’s. Analytical procedures consider the web of I-section rigid, which doesn’t happen in reality. In contrast, numerical methods include deflection of the web during the buckling. Models of beam with the effective length equal to the span, with both flanges free to move laterally and subjected to uniform bending moment was used to compare. In order to reach representative results models was varied with different length of the beams, web slenderness and flange slenderness. It was concluded that the influence of the effect of web distortion in the value of the elastic critical moment increases with the increase of the web slenderness and with the decrease of the flange slenderness and of the length. In some situations, the disregard of this effect can lead to unsafe results, while in others situations this effect has little influence on the critical elastic moment, can be unvalued.