Initial geometric imperfections: a robust, closed-section cold-formed box profile application subject to local buckling

Initial geometric imperfections are important for simulating local buckling in numerical models. References are found in the technical literature regarding open-section cold formed profiles. This work presents new procedures applied to a robust and closed-section cold formed profile subject to local buckling, and the use of procedures described in the technical literature already successfully used for open section profiles. The difference of this work in relation to the research already carried out is in the type of profile studied, in the mode of failure of the same and in the form of determination of the initial imperfections. The object of study of this work is a closed-section cold formed box profile with a short length when compared with its cross section and with local buckling failure mode. The strategies used in the present work to consider the initial geometric imperfections were to perform the linear stability analysis using the finite element method to obtain the local buckling mode that represents the deformed box profile geometry, to apply a multiplication factor in the displacements, replace the new geometry node coordinates for all profile nodes to induce the local buckling deformation mode, with model validation through experimental testing and the Effective Width Method (MLE) (ABNT NBR 14762 [1]). Finally, using the results of the collapse load of the experimental trial as a basis, it was possible to compare the results obtained by MLE and MEF. Thus, the presentation of this work used a methodology that describes the local buckling behavior and verified the precepts of the existing norms on the subject, combining theoretical and experimental methods, as they bring a better understanding of the structural problem in question.