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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18 resultados
Resultados da Pesquisa
Item Modal identification of bridge 44 of the Carajás railroad and numerical modeling using the finite element method.(2020) Silva, Marcela Santos da; Neves, Francisco de Assis dasRegular use and the effects of time can affect the behavior of a structure. Over time, problems such as the occurrence of small fissures, oxidation of steel elements, and excessive displacements at some points may arise in a structure. In this context, the monitoring of structures through experimental tests has gained more importance, because it allows for the identification of the dynamic characteristics (natural frequencies, mode shapes, and damping rate) of structures. The dynamic characteristics can be obtained through forced vibration tests, which are based on measuring the response of a structure subjected to an excitation of known magnitude, or through tests in which only the structural response is measured, such as free vibration and ambient vibration tests. The present study aims to identify the modal parameters of bridge 44 of the Carajás Railroad, using experimental data obtained on site by monitoring the vibration caused by a group of people jumping, and it compares them with the results obtained through numerical modeling performed using the finite element method, developed in CSiBridge. The modal parameters were obtained using the commercial software ARTeMIS Modal, and stochastic subspace identification was used for modal identification.Item Dynamic substructuring by the craig–bampton method applied to frames.(2020) Mapa, Lidianne de Paula Pinto; Neves, Francisco de Assis das; Guimarães, Gustavo PaulinelliPurpose The Craig–Bampton method is a substructuring technique that reduces the number of internal degrees of freedom of substructures by approximations, using a set of truncated vibration modes. It is useful for structural designs with many degrees of freedom. This work aims to develop substructuring through the Craig–Bampton method for free vibration analysis on planar frames according to the frequency range of interest. Methods The fnite-element models of diferent substructures were assembled. Thus, the degrees of physical freedom were reduced according to the frequency range of interest. The reduced-order models were coupled. Thus, the physical response was obtained. Detailed calculation and the algorithm fowchart are provided. Conclusions The study of frame dynamics using the present method in diferent frequency ranges of interest was presented and validated with the results of a commercial software. It was possible to clarify the coupling formulations of the component mode synthesis, as well as the amount of reduction of the number of equations provided by the method, reaching less than 4% of the complete model, for the considered cases.Item Optimization of partially connected composite beams using nonlinear programming.(2020) Silva, Amilton Rodrigues da; Neves, Francisco de Assis das; Sousa Junior, João Batista Marques deDue to concrete being consistently used in the filling of prefabricated linear steel structural floor slabs, the practice of constructing steel-concrete composite structures is becoming more and more popular. The joint action of the two materials is generally ensured by mechanical connectors that considerably increase the performance of the composite element structure. For a majority of practical cases, these elements are formed by a concrete slab connected to I-shaped steel beams. In this study, models of finite elements for the steel-concrete composite beams with partial interaction are optimized using the sequential linear programming algorithm. The design variables are considered with two approaches: in the first, only the parameters that define the cross section of the steel “I” profile vary, while in the second, besides the aforementioned parameters that define the cross section of the “I” profile, also considered are those that define the concrete section. In addition, the optimum distribution of the shear connectors along the composite beam are verified; in other words, the longitudinal rigidity of the deformable connection is considered to be a design variable. The design constraints are those defined in standard specifications referring to the dimensioning of concrete, steel and composite steel-concrete structures, as well as the side constraints with respect to the parameters defining the cross section and the step-size for the non-linear optimization algorithm. The results for the composite beam optimization problems are presented taking into consideration different boundary conditions. For a given optimized project, the analysis of the results is done regarding the influence of the constraints on the optimization process, the graph of the load-slip curve along the composite beam, and the values obtained for the design variables.Item 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 RochaProblemas 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.Item Dynamic analysis of composite beam and floors with deformable connection using plate, bar and interface elements.(2019) Machado, Wanderson Gonçalves; Silva, Amilton Rodrigues da; Neves, Francisco de Assis dasNew architectural tendencies combined with more resistant materials and increasingly efficient structural systems, results in projects that are safe for ultimate load capacity, but with problems related to service loads, i.e., the structure doesn’t collapse, but causes discomfort to the user. Structures with deformable connection are formed by the association of two or more structural elements by means of a deformable shear connection. In construction the most common cases of this type of structures are steel-concrete composite structures. Among these, the composite beams and floors are more susceptible to be excited by dynamic loading induced by human rhythmic activities, as walking, dancing, jumping, among others. The objective of this work is, from the three dynamic finite element formulation (plate, bar and interface), to show the efficiency of these in simulation of composite floors and beams with deformable connection under dynamic loading, where the deformable shear connection is simulated by the interface element, being the main contribution of this work. The proposed analysis model is tested and validated by means of frequency analysis results and natural vibration modes of composite floors and beams, as well as the calculation of displacements and accelerations of those when subjected to dynamic loads due the rhythmic activities. Another contribution of the model proposed in this article is the verification of the influence of the “shear lag” effect in the determination of the natural frequencies and vibration modes of composite beams, which cannot be evaluated when analyzed only for bar and interface elements.Item Multi-objective topology optimization using the Boundary Element Method.(2019) Simonetti, Hélio Luiz; Almeida, Valério da Silva; Neves, Francisco de Assis das; Greco, MarceloThis article aims to explore the application of an evolutionary optimization technique for multi-objective optimization problems using as criteria the minimization of von Mises maximum stress and minimization of the maximum growth of internal structural strain energy. To evaluate the overall effect on the optimal design configuration, due to the removal of inefficient material from the structure by using these two optimization criteria, a goal weighting scheme is adopted, whereby the weight factors emphasize and balance the stress and strain energy criteria. Also considered in this study was the method of the exponentially weighted criterion for multi-objective optimization and the Pareto optimal concept. Thus, a contribution is made to the study of these two methods in the structural optimization procedure using a linear analysis by the Boundary Element Method. Four examples are presented to demonstrate the ability of the proposed method to solve structural design problems using multi-objective optimization.Item On the nonlinear transient analysis of planar steel frames with semi-rigid connections : from fundamentals to algorithms and numerical studies.(2018) Silva, Andréa Regina Dias da; Batelo, Everton André Pimentel; Neves, Francisco de Assis das; Gonçalves, Paulo BatistaThis paper presents the fundamentals for prediction of a more realistic behavior of planar steel frames with semi-rigid connections under dynamic loading. The majority of the research in this area concentrates on the nonlinear static analysis of frames with semi-rigid connections. Indeed, few studies have contributed to the nonlinear dynamic and vibration analyses of frames. Therefore, this article first describes the frames’ semi-rigid connection behavior under monotonic and cyclic loads, and presents the independent hardening technique adopted to simulate the joint behavior under cyclic excitation. In a finite element context, this paper presents an efficient numerical methodology that is proposed in algorithmic form to obtain the nonlinear transient response of the structural system. The paper also presents, in algorithmic form, a complete description of the adopted connection hysteretic model. Satisfying the equilibrium and compatibility conditions, and assuming only the connection’s rotational deformation due to bending as variable, this work obtains the tangent stiffness and mass matrices of the beam-column element with semi-rigid connections at the ends. The study concludes by verifying and validating the proposed numerical approach using four structural steel systems: a L-frame, a two-story frame, a six-story frame, and a four-bay five-story frame. The analyses show that the hysteresis of the semi-rigid connection has a strong effect on the frames’ responses and is an important source of damping during the structural vibration.Item Smoothing evolutionary structural optimization for structures with displacement or natural frequency constraints.(2018) Simonetti, Hélio Luiz; Almeida, Valério da Silva; Neves, Francisco de Assis dasThe Smoothing Evolutionary Structural Optimization (SESO) technique was extended to solve 2D elastic problems with constraint of displacements or natural frequencies. At the end of each finite element analysis, a scalar representing the sensitivity due to the removal of an element is calculated. Thus, the elements that have the lowest values are removed from the structure, while the displacements in prescribed locations are kept inside of limits stated or the first frequencies are maximized. The proposed technique proved to be adequate and efficient in the execution of shape and topological optimization.Item Parametric modal dynamic analysis of steel-concrete composite beams with deformable shear connection.(2017) Lima, Wanderson Geraldo de; Neves, Francisco de Assis das; Sousa Junior, João Batista Marques deComposite structural elements of steel-concrete began to be used only in 1960 after the development of methods and constructive dispositions that ensured the functionality of these two materials together. In order to verify the importance of the participation of the axial mode in the frequency spectrum of the free vibration problem in composite beams with deformable shear connection, several analyses for 4 different boundary conditions and stiffness connection variation were performed. The analysis of the problem was carried out by development and computational implementation of a finite element for composite beams with partial interaction in the longitudinal direction applied to the problem of free vibrations. The solutions to this problem in the literature are scarce, and project recommendations are simplified. The results show that the finite element exhibits an excellent performance compared with the analytical results and as the axial mode has a high modal contribution, despite the boundary condition and stiffness connection.Item Optimal strut-and-tie models using smooth evolutionary structural optimization.(2016) Simonetti, Hélio Luiz; Almeida, Valério da Silva; Oliveira Neto, Luttgardes de; Neves, Francisco de Assis dasO presente artigo apresenta um procedimento numérico para a obtenção de algumas configurações dos modelos clássicos de bielas e tirantes para certas aplicações estruturais. Para isso, faz-se o uso do método dos elementos finitos com o uso de uma formulação em teoria elasto-linear plana para a geração do elemento finito. Esse procedimento de análise é acoplado com um processo de otimização topológica denominado de SESO - Smoothing Evolutionary Structural Optimization. Esse método SESO baseia-se no procedimento de diminuição progressiva da contribuição de rigidez de elementos ineficientes com menores tensões até que ele não tenha mais influência, como se este estivesse em processo de danificação. São avaliados e comparados alguns exemplos de estruturas onde já se conhece a configuração ótima obtida dos modelos clássicos de bielas e tirantes, onde se demonstra a potencialidade da presente formulação para aplicações em estruturas genéricas.