Resumo Neste trabalho é apresentado um estudo sobre a ruptura do concreto por pry-out em conectores de cisalhamento tipo Crestbond com o objetivo de obter um modelo de cálculo que estima a resistência da conexão a esse modo de falha. As análises foram realizadas por meio de simulações numéricas capazes de reproduzir o referido modo de falha. Os resultados numéricos são comparados com os experimentais e discutidos em relação à força máxima atingida e o aspecto da fissuração típica do pry-out. O modelo de cálculo proposto apresentou boa correspondência com os resultados experimentais, com uma razão média Pteo/Pexp igual a 0,99 e um coeficiente de variação de 10%. Os valores encontrados nesse estudo sugerem que a expressão da Aprovação Técnica Alemã para outros conectores pode ser aplicada nos conectores Crestbond.

Abstract In this work, a study on failure by concrete pry-out in Crestbond shear connectors is presented. The study’s aim was the development of an expression that estimates the connection’s bearing capacity. The analyses were carried out through numerical simulations designed to reproduce the referred failure mode. Numerical and experimental results are compared and discussed in relation to the maximum force reached and the cracking aspect typical of concrete pry-out. The proposed equation corresponded well to experimental results, with a mean ratio Ptheo/Pexp equal to 0,99 and a coefficient of variation of 10%. The results found in this study indicate that the concrete pry-out expression in German Technical Approval Z-26.4-56 can also be applied to Crestbond shear connectors.

Resumo Neste artigo, uma análise numérica usando método dos elementos finitos, com apoio do software Ansys, é realizada para avaliar a influência de enrijecedores transversais soldados à alma do perfil de aço na rigidez lateral e no momento fletor resistente de vigas mistas contínuas de aço e concreto à flambagem lateral com distorção (FLD). O modelo numérico desenvolvido foi validado por meio de comparação com os resultados de ensaios realizados por outro pesquisador. Na sequência, foi feita uma análise paramétrica, para vigas com dois e três vãos, variando-se o espaçamento entre os enrijecedores. Finalmente, com base nas análises realizadas, conclui-se que os enrijecedores transversais podem aumentar significativamente a rigidez lateral e o momento resistente de vigas mistas contínuas e um procedimento de cálculo para se obter esse momento, tendo como referência as prescrições da norma brasileira ABNT NBR 8800:2008, é proposto.

Abstract In this paper, a numerical analysis using the finite element method, employing the commercial code Ansys, is performed to evaluate the influence of transverse stiffeners welded to the web of the steel profile on the lateral stiffness and resistant bending moment of continuous steel and concrete composite beams subjected to lateral-torsional buckling (LTB). The developed numerical model was validated by comparison with the results of tests performed by another researcher. Subsequently, a parametric analysis was carried out for beams with two and three spans, varying the spacing between the stiffeners. Finally, based on the analysis performed, it was concluded that the transverse stiffeners can significantly increase the lateral stiffness and the resistant moment of continuous composite beams. A calculation procedure to obtain this moment is proposed, having as reference the prescriptions of the Brazilian standard ABNT NBR 8800:2008.

Abstract This article reports on a preliminary investigation about the effect of concentrated transversal force on the bending moment resistance of rectangular hollow steel section (RHS) beams. Two six-meter-long specimens with yield strength of 300 MPa and cross-section size of 250×150×6.4 mm were subjected to bending tests using a four-point load configuration. A three-dimensional nonlinear finite element model was developed by using the software ABAQUS to simulate the flexural behavior of the RHS beams. The model was validated against the experimental results and subsequently used to conduct a parametric study. The investigated parameters were the force application method and the corner radius between the webs and the flanges of the rectangular tube. The results showed that RHS beams may undergo failure due to large localized plastic deformations beneath the concentrated force, whenever this force causes compression on the webs. The use of a doubler plate on both webs can significantly reduce the detrimental effect on the bending moment resistance. Moreover, the effect is shown to be more pronounced for rectangular hollow steel sections with larger corner radius.

Abstract This research presents a study of the behavior of built-up compressed steel members composed of concentric hot rolled circular hollow sections. The use of these members is an innovative solution of practical interest for situations in which a single member does not reach the required compressive strength. Some technically and economically viable design and fabrication solutions to built-up members composed of concentric hot rolled circular hollow sections are presented. For the validation of numerical results, models of singular hollow sections are made and compared to the EN 1993-1-1, and the results obtained with numerical models were satisfactory. The compression resistance of these numerical models differs less than 9% from the EN 1993-1-1 values. Once the numerical modeling was validated, the study of built-up members was made, considering the tubes always united at the extremities by end plates, and along the length by fixed interconnections or sliding interconnections or, furthermore, without interconnections. For these three different conditions, several numerical models using FEM via Abaqus software were simulated to obtain and compare the compression resistance. The results show that these built-up sections with fixed and sliding interconnections have very similar behavior to the results obtained with European Standard procedure, when considering equivalent areas and inertias for the built-up section. Also, it shows that this observation does not apply to the sections without interconnections. Comparative graphs of compression resistance curves were generated, as also some graphs that show the distribution of the compressive force between each member of the built-up section. Finally, a formulation for the design of built-up sections without interconnections along the tubes was proposed to avoid robust computational methods.

Abstract The Hercílio Luz suspension bridge, built in 1926, has been out of service since 1991 due to high corrosion levels and structural element impairment. A complete rehabilitation project was developed which included the replacement of the impaired items and foundation strengthening. For this, an auxiliary structure was employed to support the central span during the rehabilitation process. A carefully studied load transfer process, where the central span loading is transferred from the eye-bar towards the auxiliary structure will be performed. For this purpose, a synchronized jacking sequence will be used, which was predefined by means of numerical model analysis. All structural elements had their designs evaluated and some geometric changes were implemented. This paper presents all the methodology developed in the rehabilitation project of Hercilio Luz bridge, as well as the development stages up to the present date.

Resumo Neste trabalho é estudado o processo de projeto baseado em desempenho por meio do desenvolvimento de modelos paramétricos e algorítmicos, integrando análise estrutural ao design para a geração de estruturas geométricas complexas, com base em parâmetros de produção e montagem. Essa metodologia baseia-se no Modelo Performativo, em que a forma é gerada utilizando-se critérios de desempenho. Nessa abordagem o desenvolvimento de estruturas complexas só é possível pela reversão do processo de concepção da forma, cuja geração está atrelada aos parâmetros de geometria, material e carregamento. Assim, o engenheiro estrutural não participa apenas da fase de avaliação, mas também das fases iniciais do processo, criando um processo de pesquisa e produção de conhecimento comum entre os arquitetos e engenheiros. Para investigar essa abordagem, neste artigo é feita a concepção da estrutura de uma torre de energia eólica.

Abstract This paper presents a study based on the performance design process by using parametric and algorithmic models development. This study integrates the structural analysis and the design to generate complex geometric structures, based on manufacture and assembly parameters. The used methodology is based on the Performative Model, in which the structure shape is generated using performance criteria. In this perspective, the complex structures development is only possible by reverting de shape conception process, in which its generation is linked to the geometric, material and load parameters. Therefore, the structural engineer not only participates in the evaluation phase, but also in the early stages, creating an exploration and production process of common knowledge among architects and engineers. For the purpose of investigating this approach, this work presents the design of a conceptual lattice wind tower.

Abstract Static and dynamic effects on power transmission towers can be evaluated by methodologies available in codes, which suggest the use of linear static analysis. By using numerical simulations, it is possible to observe the strong influence of the geometric nonlinear behavior of transmission cables. Dynamic effects also strongly influence this behavior, with the possibility of resonance between the cables and the structure, but up to the moment, the existent analysis procedures have not been completely validated on an experimental basis. In order to validate a complete analysis methodology, experimental procedures are proposed for a suspension tower of a 138kV transmission line in use. A tridimensional anemometer was installed on this structure in order to measure the values and directions of wind speeds. Simultaneous strain values were collected on the main elements of the tower through optical extensometers. Optical sensor technology with Fiber Bragg Gratings was used, due to the characteristic of immunity to the electromagnetic field occasioned by high electric currents. The string swing angle was evaluated through a high-resolution camera and a tridimensional accelerometer. With this instrumentation, it is possible to create a complete database that correlates wind speeds with the responses of the structural set. At the moment, 5 months of data have been collected and the instrumentation is in the final testing phase and synchronized. After this step, real-time measurements will be performed.

Esse artigo apresenta, inicialmente, um breve histórico dos trabalhos de revisão da norma brasileira de projeto de estruturas de aço e mistas de aço e concreto, que culminaram no projeto de norma de setembro de 2006, denominado aqui de PR NBR 8800:2006. Em seguida, procura fornecer as bases utilizadas na produção do PR NBR 8800:2006, as diretrizes fundamentais seguidas e as principais mudanças ocorridas em relação à norma em vigência, datada de 1986. Finalmente, procura destacar a importância de se ter uma norma atualizada para o avanço consistente da construção metálica no Brasil.

This paper starts with a historical account of the revision work being done on the Brazilian Standard for the design of steel structures and steel/concrete structures. This revision led to the September 2006 draft, here referred to as PR NBR 8800:2006. The paper then presents the basis for the development of PR NBR 8800:2006, its main guidelines and the main changes in relation to the valid Standard, released in 1986. Finally, the importance of having an up to date norm for the consistent advance of the steel construction in Brazil is highlighted.

Desenvolveu-se um modelo de elementos finitos para análise da flambagem lateral com torção de vigas com alma senoidal, levando em conta aspectos importantes como tensões residuais e imperfeições iniciais. O modelo desenvolvido foi validado por meio de comparação com os resultados de quatro ensaios experimentais. Inicialmente faz-se uma análise de autovalores e autovetores do modelo, determinando-se, assim, cargas e modos de flambagem com base na teoria linearizada de flambagem. A geometria original do modelo é alterada conforme o primeiro modo de flambagem, associando-se ao maior deslocamento a imperfeição inicial desejada. Faz-se, então, uma análise plástica incremental, considerando-se teoria de grandes deslocamentos, até que a degeneração física ou geométrica do sistema não permita novos incrementos do carregamento. São apresentadas as comparações entre resultados numéricos e experimentais, bem como comparações dos resultados de oito análises numéricas com as previsões de um procedimento baseado na norma NBR 8800 (1986). Para essas últimas comparações, foram escolhidos 6 modelos cuja instabilidade ocorre fora do regime elástico e 2 no regime elástico. Na aplicação da norma, desprezou-se a alma senoidal no cálculo das propriedades geométricas.

A Finite Element model was developed in order to study the behavior of beams with sinusoidal webs, subjected to Lateral Torsion Buckling, taking into account residual stresses and initial imperfections. The numerical model was validated by comparison with four experimental tests. To start the analysis of the model, a linear buckling analysis is made to find the first eigenvalue and the correspondent buckling mode. The next step is to assign the buckling mode to the geometrical model and the initial imperfection to the maximum mode displacement. Then an incremental plastic analysis is done, taking into account large deflections, until the model is unable to take on any other load increments due to physical or geometrical degeneration. Comparisons between numerical and experimental results are included. Comparisons between the results of eight numerical analyses and the correspondent provisions of a procedure based on the Brazilian code NBR 8800 (1986) are also included. For these eight comparisons 6 models were chosen to reach instability in the inelastic range and 2 in the elastic range. The sinusoidal web was ignored for the calculation of the geometrical properties.

Apresentam-se os procedimentos para dimensionamento de pilares mistos de aço e concreto do projeto de revisão da norma brasileira ABNT NBR 8800:1986, quando da atuação conjunta de força axial de compressão e momentos fletores. São, também, apresentadas as bases teóricas dos procedimentos, que têm como referências principais a norma européia EN 1994-1-1:2004 e a americana ANSI/AISC 360-05. Mostra-se, ainda, que os resultados fornecidos pelos procedimentos do projeto de revisão têm boa concordância com resultados mais precisos obtidos por uma análise pelo método dos elementos finitos.

This paper presents the design methods for steel and concrete composite columns subjected to compression axial load and bending moments according to the Revision Project of the Brazilian Code ABNT NBR 8800:1986. Presented also is the theoretical basis of the methods, using the European Standard EN 1994-1-1:2004 as a main guideline and the American Standard ANSI/AISC 360-05. It is showed that the results issued from the Revision Project of the Brazilian Code are in good agreement with more accurate results obtained by the finite element method.

É descrito o comportamento da estrutura de perfis formados a frio (PFF) submetida ao incêndio ocorrido em um apartamento de um conjunto habitacional de baixo custo, com quatro blocos idênticos de quatro pavimentos e oito apartamentos por andar. Cada apartamento tem 44 m² de área total. Segundo a Norma Brasileira, esse tipo de edifício é isento de verificação estrutural em situação de incêndio. Foram realizados ensaios para a caracterização do aço empregado nos pilares e vigas e ensaios metalográficos para estimar a temperatura atingida pelo aço durante o incêndio. O modelamento CFD (Computational Fluid Dynamics) do cenário do incêndio foi feito utilizando-se o programa de computador SMARTFIRE. A análise térmica da estrutura de aço em situação de incêndio foi realizada por meio do programa SUPERTEMPCALC. A verificação estrutural foi feita empregando-se as expressões da Norma Brasileira para o projeto dos PFF em temperatura ambiente, com base no AISI/USA, mas usando os fatores de redução de resistência recomendados pelo Eurocode 3 part1.2.

This paper describes the behavior of a cold-formed steel (CFS) framed structure in response to a real fire that occurred in a residential apartment. A set of residential buildings is composed by four identical four-story blocks of eight apartments per floor, housed by poor people; each apartment has 44 m² of total area. The Brazilian Code does not require that this type of building be checked for fire safety. A real fire in a residential apartment was modeled, as well the structural fire resistance; the maximum fire temperature reached during the burning on the structural material was assessed by scanning electron microscopy tests for the further comparative analysis between the theoretical and actual results. A CFD scenario representative of the actual building geometry, materials and fire behavior was modeled by means of the software SMARTFIRE. A steel thermal analysis in fire situation was conducted by means the software SUPERTEMPCALC, and the structural analysis of the steel frame was performed according to the expressions recommended by the Brazilian Standard for design of CFS for room temperature, based on the AISI/USA, but using the strength reduction factors recommended by Eurocode 3 part1.2.