EM - Escola de Minas

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6

Notícias

A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.

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Filtros

2003 - 200982010 - 2019132020 - 20223

Configurações

Autor: search.filters.author.Freitas, Marcílio Sousa da Rocha

Resultados da Pesquisa

Agora exibindo 1 - 10 de 24
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    Resistance factor calibration for perforated cold-formed steel compression members.
    (2022) Jardim, Roberta Layra Faragó; Freitas, Marcílio Sousa da Rocha; Brandão, André Luis Riqueira
    Cold-formed Steel profiles are structural profiles widely used in civil construction. They are often manufactured with perforations. The designing can be performed using the direct resistance method. Formulations were adapted by Moen and Schafer (2008) to consider the presence of perforations in these profiles. The objective of this study is to investigate the structural safety of columns with web perforations. The calculation of the resistance capacity was performed using the formulations proposed by the authors. The reliability indexes were determined using the First Order Reliability Method (FORM), First Order Second Moment (FOSM) and Monte Carlo Method (MCM), which are reliability methods for the Load and Resistance Factor Design (LRFD) and Limit States Design (LSD) philosophies. Following the same criteria performed by AISI S100, the resistance factors were obtained from the FOSM method. Based on the results, it was found that the desired security level for the LSD philosophy was not achieved. The calculated resistance factors are predominantly lower than the target. However, for the LRFD philosophy, the safety level was achieved, and the resistance factors were higher than the target.
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    Reliability assessment of cold-formed steel beams by the FORM method.
    (2021) Toledo, Fernanda Ferra Andrade; Freitas, Marcílio Sousa da Rocha; Brandão, André Luis Riqueira
    This article presents a procedure for the reliability assessment of cold-formed steel beams based on the Direct Strength Method (DSM) and the Effective Section Method (ESM). Using a comprehensive database, a statistical analysis of the test results was performed to determine the statistical properties of the professional factor random variable. The statistical parameters related to material strength, geometric properties and load effects were obtained from established references for reliability analysis. Safety levels compatible with the North American and the Brazilian codes relating to structural design of cold-formed steel members have been established. The first-order reliability method (FORM) was used to calculate resistance factors φ for usual nominal live-dead ratios. The results of the reliability analysis showed that the DSM and ESM design methods have similar levels of reliability. The same resistance factor as the DSM can be used for the ESM, without compromising the minimum level of reliability established. The results obtained with the LRFD calibration data, presented a good approximation with the load factor φ = 0.90, except for the distortional mode. With the LSD calibration data, values well below the specified were required in order to achieve the required level of reliability. It was also found that the load factor γ = 1.25, in the format of the Brazilian standard, could reach the safety requirements established for all buckling modes.
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    Dynamic risk calculation model applied to gas compressor.
    (2020) Thom, Frederico Carlos Maciel; Zoghbi, João Roberto Bastos; Freitas, Marcílio Sousa da Rocha; Sisquini, Geraldo Rossoni
    The present article proposes to apply a Risk-Based Maintenance methodology in a gas compression system. This risk calculation is based on a semi-quantitative mathematical model that uses the interdependence of process variables and predictive maintenance data applied in a Condition-Based Maintenance methodology, in order to obtain the calculation of the dynamic risk. This promotes a review of maintenance and reliability strategies proactively in real time. The dynamic risk applied to the system involves the interface of predictive maintenance and process variables with the reliability and risk analyses of the system. This value, which is associated with the financial aspects, safety, people and environment, can be compared to the tolerable risk of production plant operation, providing operation or maintenance decisions. An example demonstrates the integration of process and maintenance data using this model methodology for a gas compression system. This framework can be applied to evaluate the integrity of systems, providing critical risk-based information for the maintenance and operation teams, assisting then in the mitigation of failures in the production systems.
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    Confiabilidade estrutural de pórticos de aço.
    (2019) Mapa, Danilo Luiz Santana; Freitas, Marcílio Sousa da Rocha; Silveira, Ricardo Azoubel da Mota; Silva, Andréa Regina Dias da
    O emprego de métodos para análise de confiabilidade estrutural permite a avaliação da probabilidade de violação de estados limites relevantes ao projeto estrutural. Este artigo apresenta procedimento numérico preciso e eficiente para avaliação da confiabilidade de pórticos planos de aço via análise estrutural avançada em elementos finitos, considerando os efeitos da não linearidade geométrica e da flexibilidade das ligações. O método analítico FORM (First Order Reliability Method) foi empregado na avaliação da probabilidade de falha de funções de desempenho formuladas para estados limites últimos de resistência e estados limites de serviço. Os resultados obtidos indicaram que os índices de confiabilidade dos exemplos de pórticos planos de aço analisados são significativamente afetados pela presença das ligações semirrígidas e pelos efeitos da não linearidade geométrica.
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    SORM DG - an efficient SORM based on differential geometry.
    (2019) Ferreira, Emmanoel Guasti; Freitas, Marcílio Sousa da Rocha; Pinto, José Antônio da Rocha; Sisquini, Geraldo Rossoni
    The first order reliability method (FORM) efficiently performs first order structural reliability analysis, but with limited accuracy. On the other hand, the traditional second order reliability method (SORM) was established to improve the results of FORM, but with a supplementary computational process. Proposed herein, is a new SORM, based on differential geometry making SORM more efficient without hindering accuracy. It can be used to perform the second order structural reliability analysis in engineering. A case in the geotechnical engineering field obtained from literature was solved aiming to demonstrate the ability of the analytical procedure via differential geometry. The advantages of the newly proposed approach whereby the reliability method by differential geometry (SORM DG) over the traditional SORM are discussed. The results show that the SORM DG optimizes the outcomes from FORM and achieves the accuracy of the traditional SORM, more efficiently.
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    Integration methodology of different softwares for constrained tubular truss size optimization problems.
    (2019) Lage, Carmem Miranda; Neves, Francisco de Assis das; Freitas, Marcílio Sousa da Rocha
    Problemas de otimização estrutural paramétrica de ordem prática podem envolver um grande número de variáveis e restrições, que atendam aos requisitos normativos de segurança e desempenho estrutural. A maioria dos problemas de otimização tendem a encontrar o valor mínimo da função objetivo dentro de um conjunto viável que satisfaça as restrições. Entre as técnicas de computação evolucionária, os algoritmos genéticos (AGs) tem sido utilizados com sucesso para a otimização de estruturas, incluindo os sistemas treliçados. Esse artigo propõe uma metodologia interativa automatizada para a otimização de estruturas baseado na integração de dois programas comerciais: ANSYS e MATLAB. O script desenvolvido utiliza-se do MEF para a análise da estrutura, em conjunto com os Algoritmos Genéticos para a otimização. O objetivo do artigo é avaliar a aplicabilidade, precisão e eficiência da metodologia proposta. Foram resolvidos 2 exemplos numéricos de treliças com a metodologia proposta, treliça clássica da literatura e treliça com restrições normativas. Os resultados mostram que a metodologia é adequada para a solução de problemas de otimização estrutural paramétrica com uma boa precisão dos resultados.
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    Vibration behavior of thin-walled steel members subjected to uniform bending.
    (2018) Dôres, Andréa Gonçalves Rodrigues das; Dinis, Pedro Borges; Camotim, Dinar Reis Zamith; Freitas, Marcílio Sousa da Rocha
    This article reports the results of an investigation on the effects of internal moments on the vibration behavior of thin-walled steel members. The analyses are based on the Generalized Beam Theory (GBT), a thin-walled bar theory accounting for crosssection in-plane deformations – its main distinctive feature is the representation of the member deformed configuration by means of a linear combination of cross-section deformation modes, multiplied by their longitudinal amplitude functions. The study concerns a simply supported T-section (with unequal flanges) members exhibiting a wide range of lengths and subjected to uniform internal moment diagrams – their magnitudes are specified as percentages of the corresponding critical buckling values. After providing a brief overview of the main concepts and procedures involved in performing a GBT-based structural analysis, the vibration behavior of load-free and loaded T-section members is addressed – the influence of the applied loadings is assessed in terms of (i) the fundamental frequency difference and (ii) the change in the corresponding vibration mode shape. For validation purposes, some GBT results are compared with values yielded by shell finite element analysis performed in the code ABAQUS (Simulia, 2008).
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    Structural reliability analysis of steel plane frames with semi-rigid connections.
    (2018) Agostini, Bruno Márcio; Freitas, Marcílio Sousa da Rocha; Silveira, Ricardo Azoubel da Mota; Silva, Andréa Regina Dias da
    The design codes for structural design traditionally establish the adoption of partial safety factors to deal with uncertainties. These standards do not allow one to know the real probabilities of failure of a structure. What is needed, from a practical and scientific point of view, is a more consistent approach, based on reliability theory. This article addresses an initial attempt at determining the safety levels of structures based on advanced analysis and design with structural reliability theory. In this context, the authors consider the effects of the geometric nonlinearity and flexibility of connections in the reliability analysis, which aims at setting a certain displacement as the service limit state. For this purpose, a computer program was written called Structural Reliability Module. This program uses a First Order Reliability Method to analyse reliability. To carry out the structural analysis of steel structures, this study uses the program Computational System for Advanced Structural Analysis. Validating the Structural Reliability Module involved comparing the results from other authors with those generated by the program. Results for the structures under study indicate the efficiency of the implemented measures. Results suggest that, when a certain displacement is set as a service limit state, the reliability of the structures under analysis are only slightly influenced by geometric nonlinearity but considerably so by semi-rigid connections.
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    Reliability analysis of typical cold-formed steel beams sections.
    (2016) Campos, Raylza Santos da Silva; Brandão, André Luis Riqueira; Freitas, Marcílio Sousa da Rocha
    This paper presents a reliability analysis of cold-formed steel beams, based on the FORM and MC simulation and using data obtained from experimental tests performed at the Johns Hopkins University, Baltimore (Schafer, 2003; 2006). This paper approached two sets of flexural tests, one referring to the failure by local buckling, and another for distortional buckling. A failure function is assembled to obtain, by taking into account the statistical parameters of the material (M), fabrication (F), and professional factors (P). The material and fabrication factors were taken from AISI standard. The professional factor was determined by comparing the tested failure loads and the predicted ultimate loads calculated from the selected design provisions. The goal of the paper is the assessment of reliability index for two nominal live-to-dead load ratios, as well as to compare the value found considering the load combinations for ultimate limit states.
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    Análise de fadiga de ligações soldadas de barras de aço tubulares.
    (2013) Lage, Carmem Miranda; Sarmanho, Arlene Maria Cunha; Freitas, Marcílio Sousa da Rocha
    Nesse trabalho é apresentada uma análise de fadiga de ligações soldadas formadas por perfis estruturais tubulares de aço. É apresentado o procedimento de estimativa de vida útil à fadiga dessas ligações por meio dos métodos da tensão geométrica e da tensão nominal, estabelecidos no CIDECT 8 e Eurocode 3, com abordagem baseada em ciclos de tensão (curvas S-N). A filosofia de projeto associada a esta abordagem é a de vida garantida, que deve proporcionar um nível aceitável de confiabilidade da estrutura sem inspeções periódicas. O modelo analisado foi o de uma ponte metálica treliçada, sendo apresentada uma discussão entre esses dois métodos abordando vantagens e limitações. Os resultados obtidos permitiram determinar qual método é melhor aplicável para uma dada situação de projeto.