As vigas mistas de aço e concreto têm sido amplamente empregadas em edifícios e pontes, havendo ampla investigação teórica e experimental a respeito da utilização de perfis laminados e soldados e conectores de cisalhamento compatíveis com esses perfis, como por exemplo, o conector tipo pino com cabeça (stud bolt) e perfil U laminado. No âmbito dos perfis formados a frio, a utilização do sistema misto ainda é incipiente, necessitando de investigações mais aprofundadas a respeito do comportamento estrutural e a adequação dos modelos de cálculo adotados para vigas mistas em perfis laminados e soldados. No Brasil, a ampla disponibilidade de aços planos tem impulsionado o emprego do sistema misto constituído por perfis formados a frio em edifícios de pequeno porte, porém, mediante concepções clássicas, o que não conduz a um aproveitamento mais racional do sistema. Neste trabalho foi investigado um sistema não-convencional de vigas mistas em perfil cartola leve preenchido com concreto, cuja conexão com a laje foi feita mediante duas soluções: conectores do tipo alça em barra chata soldados ao perfil e conectores do tipo alça em barra redonda soldados ao perfil. Foi feita avaliação do comportamento estrutural da conexão aço-concreto, via ensaios de cisalhamento direto (push-out tests), e ensaios em vigas mistas simplesmente apoiadas para avaliação da região de momento fletor positivo. Os conectores de cisalhamento apresentaram ductilidade e resistência compatíveis com as vigas mistas analisadas, e as respostas de rigidez e resistência à flexão para uma condição de interação completa comprovam que a hipótese de plastificação total da seção descreve com precisão o comportamento estrutural do sistema proposto. / The composite steel and concrete beams have been largely applied in buildings and bridges constructions, having also a large amount of theoretical and experimental investigations about the use of hot-rolled and welded shapes and shear connectors that are compatible with these members, as for an example, the stud bolt and channel connectors. In the cold-formed steel sections scope, the use of a composite steel and concrete solution is still premature, what makes necessary a higher degree of a structural behavior investigation and the adequacy of the theoretical solutions proposed, also for the composite steel and concrete hot-rolled and welded shapes. In Brazil, the high availability of steel sheets has pushed the employee of the composite system of cold-formed steel in small and mid-height buildings, however, because of classical conceptions, it doesn\'t lead too a more rational use of the system. It was investigated in this work a non-conventional lightweight composite system formed by hat-shaped beams filled with concrete, witch connection with the slab was done by means of two solutions: arc-shaped connectors in at bars welded too the section and arc-shaped connectors in round bars welded too the section. An analysis was conducted for evaluation of the structural behavior in the steel and concrete interface by push-out tests, and tests in simple two points supported beams for evaluation of the bending strength. The shear connectors showed ductility and resistance compatible with the analyzed composite beams and the stiffness and bending resistance responses for the given condition of full interaction showed that the full section plastification consideration describes with precision the structural behavior of the proposed system.

Terças e longarinas metálicas são geralmente projetadas no Brasil desconsiderando a interação com as telhas, ou seja, como barras isoladas, apesar da norma brasileira NBR 14762:2001 apresentar um procedimento de cálculo que leva em consideração tal interação (método do fator R). O comportamento estrutural do sistema terça-telha é complexo e a análise completa deve considerar a não-linearidade geométrica e física, bem como a influência do contato e da conexão terça-telha. Foram analisados modelos numéricos propostos na literatura e desenvolvido um modelo via método dos elementos finitos (MEF) que incorpora as não-linearidades e o contato terça-telha. O modelo foi calibrado com resultados experimentais e posteriormente foi realizada uma análise paramétrica, a qual permitiu gerar expressões que relacionam a força (vento de sucção) com os deslocamentos. Foi também analisada a viabilidade da aplicação do método da resistência direta (MRD) ao dimensionamento de terças restringidas pela telha, empregando o método das faixas finitas (MFF) para a análise de estabilidade elástica, em que a restrição promovida pela telha foi modelada por meio de vínculos elásticos na mesa conectada com a telha. Foram considerados dois casos de distribuição de tensões normais: (i) tensões oriundas somente da flexão e (ii) tensões oriundas da flexão e torção. Em ambos os casos o momento resistente apresentou diferenças relativamente elevadas em relação ao obtido pelo método do fator R, refletindo a necessidade de uma abordagem específica do método para o sistema terça-telha. / The structural behavior of purlin-sheeting system is complex and the complete analysis should consider the physical and geometrical nonlinearity, as well as the influence of the purlin-sheeting contact and connection. The brazilian code NBR 14762:2001 provides a design procedure to consider the interaction between a purlin or girt connected to the sheeting (factor R method). In Brazil purlins and girts are typically designed as isolated beams, without consideration for this purlin-sheeting combination. Numerical models proposed in the literature were analyzed and a finite element model (FEM) was developed considering nonlinearities and the contact between purlin and sheeting. The model was validated through experimental results and then implemented in a parametrical analysis. Expressions were generated using the parametrical results to relate the loading (wind uplift) to the displacements. The direct strength method (DSM) was analyzed to the designed of purlins restrained by sheeting. The finite strip method (FSM) was used for elastic buckling determination. The restraint applied to the sheeting was modeled using an elastic foundation on the flange connected to the sheeting. Two stress distributions were considered: (i) bending stresses and (ii) bending and warping stresses. In both cases the nominal flexural strength presented considerable differences compared to the factor R design method, reflecting the necessity of a specific study to evaluate the viability of the DSM approach for purlin design.

For decades, structural engineers have been using various conventional design approaches for assessing the strength and stability of framed structures for various loads. Today, engineers are still designing without some critical information to insure that their stability assessment yields a safe design for the life of the structure with consideration for extreme loads. Presented in this thesis is new critical information provided from the study of stability analysis and design of steel framed structures accounting for extreme loads associated to load patterns that may be experienced during their lifetime. It is conducted in five main parts. A literature survey is first carried out reviewing the previous research of analyzing frame stability including the consideration of initial geometric imperfections, and also evaluating research of the analysis and design of the increased usage of cold-formed steel (CFS) storage racks. Secondly, the elastic buckling loads for single-storey unbraced steel frames subjected to variable loading is extended to multi-storey unbraced steel frames. The formulations and procedures are developed for the multi-storey unbraced steel frames subjected to variable loading using the storey-based buckling method. Numerical examples are presented as comparisons to the conventional proportional loading approach and to demonstrate the effect of connection rigidity on the maximum and minimum frame-buckling loads. Thirdly, the lateral stiffness of axially loaded columns in unbraced frames accounting for initial geometric imperfections is derived based on the storey-based buckling. A practical method of evaluating column effective length factor with explicit accounting for the initial geometric imperfections is developed and examined using numerical examples. The fourth part is an investigation of the stability for multi-storey unbraced steel frames under variable loading with accounting for initial geometric imperfections. Finally, the stability of CFS storage racks is studied. The effective length factor of CFS storage racks with accounting for the semi-rigid nature of the beam-to-column connections of such structures are evaluated based on experimental data. A parametric study on maximum and minimum frame-buckling loads with or without accounting for initial geometric imperfections is conducted. The proposed stability analysis of multi-storey unbraced frames subjected to variable loading takes into consideration the volatility of live loads during the life span of structures and frame buckling characteristics of the frames under any possible load pattern. From the proposed method, the maximum and minimum frame-buckling loads together with their associated load patterns provides critical information to clearly define the stability capacities of frames under extreme loads. This critical information in concern for the stability of structures is generally not available through a conventional proportional loading analysis. This study of work ends with an appropriate set of conclusions.

For decades, structural engineers have been using various conventional design approaches for assessing the strength and stability of framed structures for various loads. Today, engineers are still designing without some critical information to insure that their stability assessment yields a safe design for the life of the structure with consideration for extreme loads. Presented in this thesis is new critical information provided from the study of stability analysis and design of steel framed structures accounting for extreme loads associated to load patterns that may be experienced during their lifetime. It is conducted in five main parts. A literature survey is first carried out reviewing the previous research of analyzing frame stability including the consideration of initial geometric imperfections, and also evaluating research of the analysis and design of the increased usage of cold-formed steel (CFS) storage racks. Secondly, the elastic buckling loads for single-storey unbraced steel frames subjected to variable loading is extended to multi-storey unbraced steel frames. The formulations and procedures are developed for the multi-storey unbraced steel frames subjected to variable loading using the storey-based buckling method. Numerical examples are presented as comparisons to the conventional proportional loading approach and to demonstrate the effect of connection rigidity on the maximum and minimum frame-buckling loads. Thirdly, the lateral stiffness of axially loaded columns in unbraced frames accounting for initial geometric imperfections is derived based on the storey-based buckling. A practical method of evaluating column effective length factor with explicit accounting for the initial geometric imperfections is developed and examined using numerical examples. The fourth part is an investigation of the stability for multi-storey unbraced steel frames under variable loading with accounting for initial geometric imperfections. Finally, the stability of CFS storage racks is studied. The effective length factor of CFS storage racks with accounting for the semi-rigid nature of the beam-to-column connections of such structures are evaluated based on experimental data. A parametric study on maximum and minimum frame-buckling loads with or without accounting for initial geometric imperfections is conducted. The proposed stability analysis of multi-storey unbraced frames subjected to variable loading takes into consideration the volatility of live loads during the life span of structures and frame buckling characteristics of the frames under any possible load pattern. From the proposed method, the maximum and minimum frame-buckling loads together with their associated load patterns provides critical information to clearly define the stability capacities of frames under extreme loads. This critical information in concern for the stability of structures is generally not available through a conventional proportional loading analysis. This study of work ends with an appropriate set of conclusions.

Cold-formed steel structures have been in service for many years and are used as shelters for both domestic and industrial purposes. To produce an economical product, manufacturers have typically based their designs on the simple portal frame concept. As there is almost a direct relationship between overall cost and the weight of steel in a portal frame structure, it is of great importance to provide a structure with the minimum amount of steel whilst providing structural adequacy. Portal frame sheds have been refined continuously for many years, with only minimal amounts of savings in steel. Therefore, to provide even greater savings in steel, an innovative building system is required. Modern Garages Australia (MGA) is one of the leading cold-formed steel shed manufacturers in Queensland. MGA has recently developed such an innovative building system that has significant economic savings when compared with portal frame structures. The MGA building system has two key differences to that of the conventional portal frame system. These differences are that the MGA system has no conventional frames or framing system, and it has no purlins or girts. This results in the MGA system being completely fabricated from thin cladding, which significantly reduces the quantity of steel. However, the key problem with this building system is that the load paths and structural behaviour are unknown, and therefore the structure cannot be analysed using conventional methods. Therefore, the objectives of this research were to first investigate the structural behaviour of this new building system and its adequacy for an ultimate design wind speed of 41 m/s using full scale testing. The next objectives were to use finite element analysis to optimise the original MGA building system so that it is adequate for an ultimate design wind speed of 41 m/s, and to develop a new improved cold-formed steel building system that has greater structural efficiency than the original MGA building system. This thesis presents the details of the innovative MGA building system, full scale test setup, testing program, finite element analysis of the MGA building system and the results. Details and results from the optimisation of the MGA building system, and the development of a new improved cold-formed steel building system are also presented. The full scale experimental investigation considered the required loadings of cross wind, longitudinal wind and live load test cases and simulated them on the test structure accurately using an innovative load simulation system. The wind loads were calculated for a 41 m/s ultimate design wind speed. Full scale test program included both non-destructive and destructive tests. The finite element analyses contained in this thesis have considered cross wind, longitudinal wind and live load cases, as well as the destructive load case of the MGA building system. A number of different model types were created and their results were compared with the experimental results. In general, two main model types were created. The first type consisted of a 'strip' of the MGA building system (Strip model) and the second modelled the full structure (Full model). Both of these model types were further divided into models which contained no contact surfaces and those which contained contact surfaces to simulate the interfaces between the various components such as the brackets and cladding. The experimental test results showed that the MGA test structure is not suitable for an ultimate design wind speed of 41 m/s. This conclusion is a result of a number of observed failures that occurred during the extensive testing program. These failures included local buckling, crushing failures, and distortional buckling of the cladding panels. Extremely large deflections were also observed. It was calculated that for the MGA building system to be adequate for the design wind speed of 41 m/s, a cladding thickness of 0.8 mm was required. This also agreed well with the finite element analysis results which concluded that a cladding thickness of 0.8 mm was required. In order to avoid the increased use of steel in the building system, a new improved cold-formed steel building system was developed and its details are provided in this thesis. A finite element model of this new improved cold-formed steel building system was created and the results showed that the new building system was able to achieve a load step equivalent to an ultimate design wind speed of 50.4 m/s and was approximately 250% stiffer than the original MGA building system, without any increase in the overall weight of the building system. It is recommended that this new improved cold-formed steel building system be further developed with the aid of finite element modelling and be tested using a similar full scale testing program that was used for the original MGA building system.

Until recently, the hot-rolled steel members have been recognized as the most popular and widely used steel group, but in recent times, the use of cold-formed high strength steel members has rapidly increased. However, the structural behavior of light gauge high strength cold-formed steel members characterized by various buckling modes is not yet fully understood. The current cold-formed steel sections such as C- and Z-sections are commonly used because of their simple forming procedures and easy connections, but they suffer from certain buckling modes. It is therefore important that these buckling modes are either delayed or eliminated to increase the ultimate capacity of these members. This research is therefore aimed at developing a new cold-formed steel beam with two torsionally rigid rectangular hollow flanges and a slender web formed using intermittent screw fastening to enhance the flexural capacity while maintaining a minimum fabrication cost. This thesis describes a detailed investigation into the structural behavior of this new Rectangular Hollow Flange Beam (RHFB), subjected to flexural action The first phase of this research included experimental investigations using thirty full scale lateral buckling tests and twenty two section moment capacity tests using specially designed test rigs to simulate the required loading and support conditions. A detailed description of the experimental methods, RHFB failure modes including local, lateral distortional and lateral torsional buckling modes, and moment capacity results is presented. A comparison of experimental results with the predictions from the current design rules and other design methods is also given. The second phase of this research involved a methodical and comprehensive investigation aimed at widening the scope of finite element analysis to investigate the buckling and ultimate failure behaviours of RHFBs subjected to flexural actions. Accurate finite element models simulating the physical conditions of both lateral buckling and section moment capacity tests were developed. Comparison of experimental and finite element analysis results showed that the buckling and ultimate failure behaviour of RHFBs can be simulated well using appropriate finite element models. Finite element models simulating ideal simply supported boundary conditions and a uniform moment loading were also developed in order to use in a detailed parametric study. The parametric study results were used to review the current design rules and to develop new design formulae for RHFBs subjected to local, lateral distortional and lateral torsional buckling effects. Finite element analysis results indicate that the discontinuity due to screw fastening has a noticeable influence only for members in the intermediate slenderness region. Investigations into different combinations of thicknesses in the flange and web indicate that increasing the flange thickness is more effective than web thickness in enhancing the flexural capacity of RHFBs. The current steel design standards, AS 4100 (1998) and AS/NZS 4600 (1996) are found sufficient to predict the section moment capacity of RHFBs. However, the results indicate that the AS/NZS 4600 is more accurate for slender sections whereas AS 4100 is more accurate for compact sections. The finite element analysis results further indicate that the current design rules given in AS/NZS 4600 is adequate in predicting the member moment capacity of RHFBs subject to lateral torsional buckling effects. However, they were inadequate in predicting the capacities of RHFBs subject to lateral distortional buckling effects. This thesis has therefore developed a new design formula to predict the lateral distortional buckling strength of RHFBs. Overall, this thesis has demonstrated that the innovative RHFB sections can perform well as economically and structurally efficient flexural members. Structural engineers and designers should make use of the new design rules and the validated existing design rules to design the most optimum RHFB sections depending on the type of applications. Intermittent screw fastening method has also been shown to be structurally adequate that also minimises the fabrication cost. Product manufacturers and builders should be able to make use of this in their applications.

No presente trabalho se desenvolve como proposta principal, uma investigação experimental sobre o comportamento de elementos de aço formados a frio comprimidos em temperaturas elevadas considerando a influência da restrição ao alongamento térmico. Nessa investigação foram avaliadas as distribuições de temperaturas no contorno da seção transversal e ao longo do comprimento dos elementos. Outrossim, avaliou-se a influência da restrição ao alongamento térmico sobre o comportamento mecânico dos elementos, em especial sobre o desenvolvimento das forças de restrição que surgem durante a fase de aquecimento dos mesmos. Concernente ao comportamento térmico, os resultados indicam que a temperatura resistente de elementos expostos ao calor por todos os lados deve ser determinada com base nas medições realizadas em seções a meia altura do elemento devido à distribuição não uniforme de temperatura ao longo do comprimento. Com relação ao comportamento mecânico, os resultados experimentais mostraram que a resistência pós-crítica em temperaturas elevadas desses elementos é pequena e nesse sentido é mais coerente considerar como temperatura resistente a temperatura correspondente ao momento da perda de estabilidade dos elementos. Em caráter complementar e exploratório foram realizadas análises numéricas para melhorar o entendimento do comportamento em temperaturas elevadas dos elementos de aço formados a frio investigados experimentalmente no presente trabalho. Nas análises numéricas foi avaliada uma estratégia de modelagem em elementos finitos para simular a restrição ao alongamento térmico axial em elementos comprimidos submetidos a temperaturas elevadas. Os resultados apontam que os modelos numéricos foram eficientes para prescrever força de compressão resistente em temperaturas elevadas e o tempo resistente. Por outro lado não foram eficientes para prescrever as temperaturas críticas. No âmbito normativo foram realizadas as avaliações do método de cálculo simplificado proposto na ABNT NBR 14323 (2012) e da possibilidade de adequar o método simplificado de cálculo do EUROCODE 3 parte 1.3 (2006) para o dimensionamento em temperaturas elevadas desses elementos. Os resultados sugerem que o método de cálculo simplificado da ABNT NBR 14323 (2012) foi capaz de fornecer satisfatoriamente a força de compressão resistente dos elementos investigados que se enquadravam nas exigências do método. Outrossim, sugerem que o uso do método simplificado do EUROCODE 3 parte 1.3 (2006) com redução da resistência ao escoamento e módulo de elasticidade do aço para o dimensionamento em temperaturas elevadas de elementos de aço formados a frio carece de mais investigações. / The main proposal of this work was an experimental investigation on the behavior of cold-formed steel compressed members at elevated temperatures considering the influence of restraining to the thermal elongation. In this investigation, it was evaluated the temperature distributions on the cross section and along the height of the members. Furthermore, it was evaluated the influence of restraining to the thermal elongation on the mechanical behavior of these members, in particular on the development of restraining forces during their heating phase. Concerning the thermal behavior, the results indicate the critical temperature of members exposed to heat from all sides should be determined based on measurements performed on sections located at mid-span of the members due to the non uniform temperature distribution along the height. With regards to mechanical behavior, the experimental results showed that the post-buckling resistance at elevated temperatures of these members is small and the critical temperature should be considered as the temperature corresponding to the buckling temperature. Additionally numerical analyzes were performed to better understand the behavior of the cold-formed steel members at elevated temperatures that were experimentally investigated in this study. In the numerical analyzes a modeling strategy was evaluated on finite elements to simulate the axial restraining to the thermal elongation in compressed members subjected to high temperatures. The results show that the numerical models were effective to prescribe the ultimate loads at elevated temperatures and the critical time considering the influence of the axial restraining to the thermal elongation. On the other hand, the numerical models were not effective to prescribe the critical temperature. Within the normative scope, the design method proposed in the ABNT NBR 14323 (2012) (project revision) was evaluated as well the possibility of adapting the EUROCODE 3 part 1.3 (2006) design guidelines to the design of cold-formed steel members at elevated temperatures. The results suggest that the design method proposed in the ABNT NBR 14323 (2012) (project revision) was able to accurately predict the ultimate test loads of the members that were within the requirements of the method. On the other hand, it was found that the use of the EUROCODE 3 part 1.3 (2006) design guidelines with reduction of the mechanical properties at elevated temperatures (yield strength and elastic modulus of steel) for design of compressed cold formed steel members at elevated temperature needs further investigations.

Terças e longarinas metálicas são geralmente projetadas no Brasil desconsiderando a interação com as telhas, ou seja, como barras isoladas, apesar da norma brasileira NBR 14762:2001 apresentar um procedimento de cálculo que leva em consideração tal interação (método do fator R). O comportamento estrutural do sistema terça-telha é complexo e a análise completa deve considerar a não-linearidade geométrica e física, bem como a influência do contato e da conexão terça-telha. Foram analisados modelos numéricos propostos na literatura e desenvolvido um modelo via método dos elementos finitos (MEF) que incorpora as não-linearidades e o contato terça-telha. O modelo foi calibrado com resultados experimentais e posteriormente foi realizada uma análise paramétrica, a qual permitiu gerar expressões que relacionam a força (vento de sucção) com os deslocamentos. Foi também analisada a viabilidade da aplicação do método da resistência direta (MRD) ao dimensionamento de terças restringidas pela telha, empregando o método das faixas finitas (MFF) para a análise de estabilidade elástica, em que a restrição promovida pela telha foi modelada por meio de vínculos elásticos na mesa conectada com a telha. Foram considerados dois casos de distribuição de tensões normais: (i) tensões oriundas somente da flexão e (ii) tensões oriundas da flexão e torção. Em ambos os casos o momento resistente apresentou diferenças relativamente elevadas em relação ao obtido pelo método do fator R, refletindo a necessidade de uma abordagem específica do método para o sistema terça-telha. / The structural behavior of purlin-sheeting system is complex and the complete analysis should consider the physical and geometrical nonlinearity, as well as the influence of the purlin-sheeting contact and connection. The brazilian code NBR 14762:2001 provides a design procedure to consider the interaction between a purlin or girt connected to the sheeting (factor R method). In Brazil purlins and girts are typically designed as isolated beams, without consideration for this purlin-sheeting combination. Numerical models proposed in the literature were analyzed and a finite element model (FEM) was developed considering nonlinearities and the contact between purlin and sheeting. The model was validated through experimental results and then implemented in a parametrical analysis. Expressions were generated using the parametrical results to relate the loading (wind uplift) to the displacements. The direct strength method (DSM) was analyzed to the designed of purlins restrained by sheeting. The finite strip method (FSM) was used for elastic buckling determination. The restraint applied to the sheeting was modeled using an elastic foundation on the flange connected to the sheeting. Two stress distributions were considered: (i) bending stresses and (ii) bending and warping stresses. In both cases the nominal flexural strength presented considerable differences compared to the factor R design method, reflecting the necessity of a specific study to evaluate the viability of the DSM approach for purlin design.

As vigas mistas de aço e concreto têm sido amplamente empregadas em edifícios e pontes, havendo ampla investigação teórica e experimental a respeito da utilização de perfis laminados e soldados e conectores de cisalhamento compatíveis com esses perfis, como por exemplo, o conector tipo pino com cabeça (stud bolt) e perfil U laminado. No âmbito dos perfis formados a frio, a utilização do sistema misto ainda é incipiente, necessitando de investigações mais aprofundadas a respeito do comportamento estrutural e a adequação dos modelos de cálculo adotados para vigas mistas em perfis laminados e soldados. No Brasil, a ampla disponibilidade de aços planos tem impulsionado o emprego do sistema misto constituído por perfis formados a frio em edifícios de pequeno porte, porém, mediante concepções clássicas, o que não conduz a um aproveitamento mais racional do sistema. Neste trabalho foi investigado um sistema não-convencional de vigas mistas em perfil cartola leve preenchido com concreto, cuja conexão com a laje foi feita mediante duas soluções: conectores do tipo alça em barra chata soldados ao perfil e conectores do tipo alça em barra redonda soldados ao perfil. Foi feita avaliação do comportamento estrutural da conexão aço-concreto, via ensaios de cisalhamento direto (push-out tests), e ensaios em vigas mistas simplesmente apoiadas para avaliação da região de momento fletor positivo. Os conectores de cisalhamento apresentaram ductilidade e resistência compatíveis com as vigas mistas analisadas, e as respostas de rigidez e resistência à flexão para uma condição de interação completa comprovam que a hipótese de plastificação total da seção descreve com precisão o comportamento estrutural do sistema proposto. / The composite steel and concrete beams have been largely applied in buildings and bridges constructions, having also a large amount of theoretical and experimental investigations about the use of hot-rolled and welded shapes and shear connectors that are compatible with these members, as for an example, the stud bolt and channel connectors. In the cold-formed steel sections scope, the use of a composite steel and concrete solution is still premature, what makes necessary a higher degree of a structural behavior investigation and the adequacy of the theoretical solutions proposed, also for the composite steel and concrete hot-rolled and welded shapes. In Brazil, the high availability of steel sheets has pushed the employee of the composite system of cold-formed steel in small and mid-height buildings, however, because of classical conceptions, it doesn\'t lead too a more rational use of the system. It was investigated in this work a non-conventional lightweight composite system formed by hat-shaped beams filled with concrete, witch connection with the slab was done by means of two solutions: arc-shaped connectors in at bars welded too the section and arc-shaped connectors in round bars welded too the section. An analysis was conducted for evaluation of the structural behavior in the steel and concrete interface by push-out tests, and tests in simple two points supported beams for evaluation of the bending strength. The shear connectors showed ductility and resistance compatible with the analyzed composite beams and the stiffness and bending resistance responses for the given condition of full interaction showed that the full section plastification consideration describes with precision the structural behavior of the proposed system.

Barras compostas em dupla cantoneira são constituídas por duas seções idênticas dispostas paralelamente, afastadas entre si e ligadas uma a outra apenas em alguns pontos ao longo do comprimento, por meio de chapas separadoras. O sistema aqui apresentado é bastante utilizado, principalmente em estruturas treliçadas leves, no entanto, não existem estudos específicos sobre seu comportamento, como conseqüência as normas de cálculo não fornecem subsídios para o projeto desse componente estrutural. É relevante estudar o comportamento de barras em dupla cantoneira, já que neste caso, além dos modos de instabilidade associados à cantoneira isolada, poderão ocorrer modos de instabilidade associados à barra composta em função da presença das chapas separadoras, que tendem a modificar o comportamento do sistema. Apresenta-se no trabalho análises numérica e experimental sobre o comportamento de barras submetidas à compressão centrada e excêntrica. Nas análises variou-se o número de chapas separadoras buscando estudar a eficiência das mesmas na força normal resistente das barras. Os resultados mostraram que a introdução de chapas separadoras melhorou significativamente o comportamento das barras, principalmente para compressão excêntrica. Foram observados modos de instabilidade por flexo-torção, por flexão e combinação dos dois modos. Para comparação dos resultados, inicialmente foram adotadas duas hipóteses de cálculo com base no procedimento da ABNT NBR 14762:2010, considerando compressão centrada. No primeiro procedimento considerou-se cada cantoneira como uma barra isolada independente da presença das chapas separadoras, admitiu-se instabilidades local, por flexo-torção e por flexão; no segundo considerou-se barra composta admitindo-se apenas instabilidades local e por flexão em relação ao eixo principal de menor inércia do conjunto. Em geral, os resultados das análises numérica e experimental apresentaram valores intermediários aos obtidos pelas duas hipóteses adotadas inicialmente. Com os resultados obtidos nas análises numérica e experimental são recomendados procedimentos para o dimensionamento desse componente estrutural. / Double-angle members with batten plates consist of two identical angles set up in parallel, spaced apart, and connected to each other by batten plates at specified points along the length. The system presented herein is widely used, especially in light truss structures; however, there are no standard design procedures specific for the design of this structural component. Studying the behavior of double angle members is interesting, because in this case, besides the critical modes of the single angle, they also show critical modes, due to the presence of the batten plates that sometimes interfere with the behavior of the system. This work presents a numerical and experimental study of members under concentric and eccentric axial compression. The number of batten plates is changed to study the influence on the nominal axial strength. The use of batten plates significantly increases the strength of the system, especially for members under eccentric compression. The buckling modes observed were flexural-torsional, flexural and combination of the modes. Initially, two design hypotheses are compared to the results obtained: (i) non-composite action (no interaction between angles), with only local, flexural, and flexural-torsional buckling considered; (ii) composite action (full interaction between angles), and only considering local and minor-axis flexural buckling of the pair of angles. The two design hypotheses ignore load eccentricity. The hypotheses are based upon recommendations in ABNT NBR 14762:2010. In general, numerical and experimental results for angles connected by bolted batten plates fall in between the design curves defined by methods (i) and (ii). With the results obtained in numerical and experimental analysis, procedures are recommended for the design of this structural component.