Abstract: Brazilian standards for design of cold-formed steel (ABNT NBR 14762:2010, 2010) and design of pallet racks (ABNT NBR 15524-2:2007, 2007) have different procedures to determine the strength of columns under axial compression, using different buckling curves. This paper aims to evaluate the efficiency of using cold-formed Brazilian standard buckling design curve instead of the formulations of the pallet-rack design standard to study the use viability of the equations in the calculation procedure for computing the uprights compressive strength. This strength was calculated in four ways: one using the original equations of pallet-rack Brazilian standard, and the other three using adaptations of the buckling curve from the cold-formed steel design standard. A theoretical and numerical procedure based on finite element analysis concerning local, global, and distortional buckling and imperfections was performed. Furthermore, experimental results were also consulted to determine the effective area of studied cross-sections considering the effects of local buckling and the presence of continuous perforations. The results show that the proposed modifications are consistently correlated to the results obtained using the original equations of ABNT NBR 15524, indicating the viability of using the buckling curve of ABNT NBR 14762.

Resumo Neste trabalho foram avaliadas duas treliças mistas projetadas com perfis tubulares, associadas a uma laje maciça de concreto. Baseando-se em expressões analíticas relacionadas ao problema, seguindo as recomendações de normas, análises numéricas foram realizadas, com modelos criados utilizado o programa computacional Ansys e uma análise experimental, por meio de ensaios em laboratório com a estrutura em escala real. Houve boa aproximação dos resultados nas três análises, sendo observada a possibilidade de falha na conexão de cisalhamento em uma das treliças. Com uma mudança no comprimento do conector da segunda treliça, foi observado um aumento na resistência e na rigidez da estrutura. No estudo, ficaram evidentes os efeitos localizados da ligação entre os perfis em seção tubular e da fixação do conector de cisalhamento diretamente sobre a parede do banzo superior, que causaram plastificações também localizadas.

Abstract In the present work, two composite trusses formed by tubular shapes supporting a concrete slab were evaluated. Based on analytical formulation related to the problem, according to recommendations of standards, numerical analyses were performed, with models created using the software Ansys, and an experimental analysis with full-scale tests. Good agreement between the three analysis types was observed. A possible shear connection failure in one truss was observed. With a change in the second truss's connector length, an increase in the structure's strength and rigidity was achieved. In this study, because the shear connectors were directly welded on the upper chord wall, local effects with localized plastifications were evidenced.

Abstract This article presents a theoretical and numerical study of an innovative joint using cold-formed steel sections. The motivation for the study of this connection is the ease of manufacturing and assembly that it provides. The profiles are made of cold-formed lipped channel sections, which are welded to form closed built-up sections on the columns and open built-up lipped sections to the beams. The beams use endplates connected by bolts (threaded bars) to the columns. The study evaluates the connection’s initial stiffness of 19 models, where the following parameters were varied: the thickness of the profiles and endplates, the height of the column sections and the diameter of the bolts. A theoretical and a numerical study were developed: the numerical study was performed using finite elements through the commercial software ANSYS, whereas the theoretical study was made based on the component method, prescribed by Eurocode 3, that does not include the design of the connection analyzed herein. Thus, aiming to enable the design of joints composed of cold-formed lipped channel sections, the analysis results were compared and an adjustment coefficient, proportional to the slenderness of the column’s plates, was proposed. The coefficient was introduced to the stiffness component that represents the column web in compression in the mechanical model. The ratio between the coefficients’ numerical and theoretical values presented a maximum variation of 11%, which was considered satisfactory.