Abstract This article presents a theoretical and numerical study of bolted sleeve connections with rectangular hollow sections (RHS) under axial tension and compression. The geometric form of a hollow section provides resistance for high axial loads, torsion and combines effects, spreading its utilization in truss systems. In this context, the sleeve connections proposed explore these characteristics of RHS and offer an attractive aesthetic appearance for the continuity of elements. The bolted sleeve connection with RHS is formed by two outer tubes connected by an inner tube and staggered bolts. Herein, a parametric study was developed for identification of the failure modes in the connection. Finite element models with different geometric parameters and number of bolts were created in commercial software. The width, depth and thickness of RHS tubes and diameter of bolts were variated. In the theoretical/numerical/parametric results, the yielding gross section failure, the fracture through the effective net area failure and the bearing failure were observed. These failure modes occurred in both outer and inner tubes. The load results were compared to determine the resistance capacity of sleeve connections. The theoretical formulations were evaluated for representation of the ultimate load of the failure modes. (RHS compression loads effects systems context elements Herein software width variated theoreticalnumericalparametric observed

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 As práticas atuais em engenharia estrutural exigem cada vez mais conhecimento e expertise, em relação à estabilidade de estruturas, por parte dos profissionais da área. Este artigo implementa procedimentos normativos de análise de segunda ordem aproximada de estruturas de aço e concreto armado, com o objetivo de comparar as metodologias aproximadas entre si e com uma análise de elementos finitos geometricamente exata realizada no Ansys 14.0. Os seguintes métodos são tratados nesse trabalho: Método da Amplificação dos Esforços Solicitantes, da NBR 8800:2008; o método do Coeficiente γ z, da NBR 6118:2014; o método P-Delta iterativo e o método do Coeficiente α c r, da EN 1993-1-1:2005. É apresentada uma revisão bibliográfica a respeito dos métodos normativos e como são tratadas as não linearidades de materiais e geométricas. Exemplos numéricos estão incluídos, de onde são extraídas as informações para a comparação entre as metodologias. Em resumo, os métodos apresentados mostram boa correlação de resultados quando aplicados dentro dos respectivos limites de aplicabilidade recomendados, dos quais, o Eurocódigo 3 aparenta ter a maior faixa de aplicabilidade. Os métodos aproximados tratados mostram ser mais adequados para estruturas aporticadas regulares e sujeitas à carregamentos regulares.

abstract: Current practices in structural engineering demand ever-increasing knowledge and expertise concerning stability of structures from professionals in this field. This paper implements standardized procedures for geometrically nonlinear analysis of steel and reinforced concrete structures, with the objective of comparing methodologies with one another and with a geometrically exact finite element analysis performed with Ansys 14.0. The following methods are presented in this research: Load Amplification Method, from NBR 8800:2008; the γ z coefficient method, from NBR 6118:2014; the P-Delta iterative method and the α c r coefficient method, prescribed in EN 1993-1-1:2005. A bibliographic review focused on standardized approximate methods and models for consideration of material and geometric nonlinearities is presented. Numerical examples are included, from which information is gathered to ensure a valid comparison between methodologies. In summary, the presented methods show a good correlation of results when applied within their respective recommended applicability limits, of which, Eurocode 3 seems to present the major applicability range. The treated approximate methods show to be more suitable for regular framed structures subjected to regular load distributions.

Abstract The chord length is an essential geometric property that must be defined in the analysis of isolated joints composed of hollow steel sections, as well as the boundary conditions of the test. The analysis of these parameters’ effect on the behavior of joints has been addressed by other studies, mostly with joints between circular hollow sections with compact or semi-compact cross-sections. Recent research about tubular joints has addressed cases with slender sections, where the design of joints containing these sections is still in development. In this context, this study aimed to evaluate the effect of the chord length in the behavior of T-joints between circular hollow section braces and slender rectangular hollow section chords through experimental tests and a numerical study considering the application of axial compression at the braces. The joint behavior was examined through the load-strain and load-deformation curves and the von Mises stress distribution, which allowed the failure mode's determination and the joint resistance value. Chord face failure was observed in the prototypes. It was concluded that a minimum chord length of 0.6m would be the adequate value for the study of the T-joints containing the geometric properties used in this study, which would be equivalent to a chord length five times higher than the width of the cross-section (5b0).

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 analyzes sleeve connections between circular hollow sections. This type of connection is composed of two tubes connected by bolts to an inner tube with a smaller diameter, and explores the efficiency, aesthetics and resistance of hollow sections subjected to tension and compression. In previous researches, sleeve connections with aligned and crossed bolt dispositions and under axial tension were studied. Herein, the behavior of sleeve connections with aligned bolts and under compression was analyzed. A model to represent the connection using the finite element method was developed, which allowed a numerical analysis with geometric property variations. In the numerical/parametric results, bearing failure was observed in all cases, either in the outer or inner tube. Limiting the number of bolts to 6 and considering that connections have a lower outer thickness than the inner tube, a formulation was proposed to determine the ultimate bearing capacity of sleeve connections under compression and with bearing failure.

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.

Abstract Circular hollow sections are usually used in long-span roof truss systems. One of the typology for connecting elements in such structures involves the flattening of bar ends. This article presents the numerical analysis of a plane truss composed of circular hollow sections, in which diagonal bars have flattened ends. In this sense, a new flattening typology called stiffened flattening is proposed, characterized by a non-flat geometry, with the creation of stiffeners in the lateral edges of the diagonal flattened ends. The diagonal connecting system with the chord members uses connecting plates. The plates are welded to the chords and the diagonals are connected to latter through a single bolt. The numerical analysis using finite elements method was developed in two stages through ANSYS software with the Parametric Design Language (APDL), in which parameters such as geometry, materials, element types, boundary conditions and loads are specified. A non-linear analysis was performed using shell elements on the chords, diagonals, plates and welds, and contact elements between the diagonals with stiffened flattened ends and the connecting plates. Initially, a numerical study of the connecting node and the stiffened flattened end was performed, and the results directed the modeling of the plane truss. The numerical results were calibrated with the experimental truss results in full scale. The numerical result of the plane truss was also compared to a theoretical study, considering the axial load eccentricity applied in the diagonal with stiffened flattened ends. The study was based on the consideration of combined effects of axial force and bending moment provided by the Brazilian standard ABNT NBR 8800:2008. The final results indicate that the numerical model proposed is efficient and has good correlation with the experimental and theoretical results.

Abstract The circular hollow sections (CHS) are being widely employed in steel structures around the world, increasing the development of new researches. This article proposes an innovative connection model for circular hollow sections that facilitates and reduces the assembly cost of hollow section structures. The proposed connection is a tube sleeve, used to splice two tubes, composed of an inner tube with a diameter smaller than the connecting tubes, which is connected to the outer tubes by bolts passing through both tubes. This connection can be a cheaper and easier alternative to flange connections, which are widely used in large span tubular trusses. The connection was tested in laboratory under tension loading. The tests made it possible to identify the influence of stress distribution on tubes and the need for the use of a shear lag coefficient. The results of the ultimate load capacity demonstrated the viability of the tube sleeve connection use.