Análise numérica e classificação de secções transversais de vigas alveolares

Abstract

With the increased demand for material savings, cellular beams emerge as an important alternative to the regular I profiles. These have regularly spaced openings on the web, reducing the weight of an equivalent I profile. Even more, allowing the use of openings for technical installations. However, it is necessary to be careful due to the cellular beams are susceptible to complex and unique collapse mechanisms. To understand the behavior of the beam profile in a good way, it's necessary to start with the correct cross-section classification. Taking account of the availability of classification methods that underestimate their resistance, a numerical study is presented in order to reclassify this type of sections. A web of the cellular beam is numerically modeled as a plate element with a circular opening in the center and is subject to axial compression stress. This model is developed using the finite element method considering a variation of three parameters: geometric slenderness, the opening diameter, and the plate length. A first model is developed representing a solid plate and is calibrated according to a mathematical approach, offering good correspondence. Keeping constant the plate length, linear simulations are performed to verify the influence of an opening in the critical normalized buckling load for different geometric slenderness, obtaining, as a result, a low influence of slenderness and linear dependence for the opening diameter. The model is updated keeping constant the slenderness ratio and varying now the opening diameter and the plate length. Analitic equations that perform the three parameters relation are obtained through linear adjustment using the Software MATLAB, valid in the proposed interval with a 6% of error comparing with the the numerical results. By the critical elastic load of plates with openings, a transformation of these in normalized slenderness parameters is made in order to compare with the standard limits given by Eurocode 3, proposing a new classification methodology. Four different beam profiles are analyzed, each one representing a different cross-section class in order to compare the current recommended methodology with the new proposal. By the new methodology, as an opening becomes larger, larger is the class number, unlike the Eurocode 3 approach. Finally, the stress distribution on the plates and ultimate post-buckling loads are obtained by non-linear simulations, considering geometric imperfections, with a successfully correspondence for the proposed method.