EM - Escola de Minas

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

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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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Resultados da Pesquisa

Agora exibindo 1 - 10 de 13

Optimized reinforcement distribution in reinforced concrete structures under plane stress state.
(2022) Silva, Amilton Rodrigues da; Ladeira, Artur Hallack
The strut-and-tie model is widely used for analysis and design of reinforced concrete structures. To apply this model, it is necessary to defne strut-and-tie systems that represent the fow of stresses generated in the analyzed structure. In many situations, this strut-and-tie model is defned through an evolutionary structural optimization (ESO) considering linear isotropic material. The results obtained from this model are not always satisfactory Query ID="Q1" Text="Please confrm the inserted city name and country name in afliations 1 and 2 are correct and amend if necessary." because of the nonlinear behavior of the concrete, mainly because of the great diference in the behavior under tension and compression. Because of this, an evolutionary algorithm is developed in this article to defne the optimized reinforcement distribution in reinforced concrete structures under plane stress state, considering the nonlinearity of the materials. This algorithm adopts the same principle as the ESO algorithm; however, it does not eliminate the mesh element that discretizes the analyzed domain, but it eliminates the reinforcement of the elements that do not meet an efciency criterion. A three-node triangular fnite element is used for nonlinear analysis of the reinforced concrete structure under plane stress state. The structure domain is discretized by this element, which can be of four types: with reinforcement in two fxed orthogonal directions, only in one direction, or without reinforcement. During the evolutionary process of the algorithm using a rejection criterion based on the level of reinforcement strain, the elements with reinforcement are changed to elements without reinforcement or with reinforcement in only one direction. Three practical applications were evaluated to verify the efciency of the algorithm proposed in this article. Two of them had their results compared with results provided in the literature, verifying the efciency of the proposed algorithm.
Parametric study using a curved shell finite element to dynamic analysis of footbridge under rhythmic loading.
(2021) Becerra, Humberto Cardona; Silva, Amilton Rodrigues da
When designing structural systems, the relation between form and structure is not always considered, because architects and engineers work independently. Structures with mutual collaboration such as surface-active (e.g., shells) when well-designed can optimize specific behaviors. This work proposes an analysis of some parameters that influence the dynamic behavior of footbridges under rhythmic loading. The variation of these parameters allows defining different mass distribution along the footbridge with a constant total weight. The relation between form and structure was also analyzed in this parametric study considering two architectural models for the footbridges. The parametric study proposed required a dynamic analysis of shells with variable thickness. Therefore, the formulation of a curved shell finite element is presented. This element is based on a degenerate three-dimensional solid element and is restricted to the behavior of shell under the Reissner–Mindlin approach. Two classic examples from the literature and the analytical solution of a long cylindrical shell under membrane and bending behavior were used in the validation of the curved shell finite element used in numerical analysis. From the proposed parametric study, results are presented for the parameters that define a better response in relation to the vibration fundamental frequencies of the footbridge and its maximum accelerations due to a rhythmic loading. It is concluded that the form of the curved shell supporting the flat slab significantly affects the footbridge dynamic behavior.
Numerical formulation for nonlinear analysis of concrete and steel shells with deformable connections.
(2021) Silva, Amilton Rodrigues da; Dias, Luís Eduardo Silveira
A two-dimensional interface finite element capable of associating flat shell elements positioned one above the other was developed. The implemented interface element can physically simulate the contact between the flat shell elements and connect the reference planes of the shell elements above and below it. The formulation presented allows consideration of nonlinear behavior for the deformable connection as well as for the concrete and steel materials that make up the shell structure. One of the practical applications analyzed in this research is the numerical simulation of composite floors formed by a reinforced concrete slab connected to steel beams through a deformable connection. In this case, the concrete slab and the steel beams are discretized by flat shell elements and the deformable connection is discretized by two-dimensional interface elements. Experimental and numerical results from literature were used to validate the implemented elements. In the two examples analyzed, the results obtained for the displacements were close, with the difference, in the first case, being associated with uncertainties during the experimental test and in the second, the difference in theories used in the formulation of the implemented elements.
Numerical analysis of steel–concrete composite beams with partial interaction : a plastic-hinge approach.
(2021) Lemes, Igor José Mendes; Dias, Luís Eduardo Silveira; Silveira, Ricardo Azoubel da Mota; Silva, Amilton Rodrigues da; Carvalho, Tawany Aparecida de
A two-dimensional displacement-based formulation with a plastic-hinge approach for the numerical analysis of composite beams with partial shear connection is presented here. The co-rotational approach is applied in the numerical model to allow large displacements and rotations. The axial and transverse displacement functions are defined to avoid locking problems. The simulation of the materials and shear connection nonlinear behaviors are approached via the strain compatibility method (SCM), where the constitutive relations are explicitly used. The slip in the steel section–concrete slab interface is considered by the axial force decomposition in the cross-section level by the degree of composite action, without introducing degrees of freedom in the finite element. The numerical proposal of the present work is tested by simulating steel–concrete composite beams and comparing the obtained results with the experimental and numerical data already known. This formulation is verified as numerically stable and without locking phenomena, and good convergence with literature results was obtained. However, more refined finite element (FE) meshes are needed.
Optimization of partially connected composite beams using nonlinear programming.
(2020) Silva, Amilton Rodrigues da; Neves, Francisco de Assis das; Sousa Junior, João Batista Marques de
Due 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.
Numerical implementation for conception of strut and tie models in reinforced concrete structures.
(2020) Ladeira, Artur Hallack; Silva, Amilton Rodrigues da; Camargos, Bruno Henrique Lourenço; Mapa, Lidianne de Paula Pinto; Reis, Reinaldo Antonio dos
O Modelo de Bielas e Tirantes pode ser uma excelente alternativa para o dimensionamento de elementos estruturais em concreto armado submetidos a estado plano de tensão e para regiões que apresentem descontinuidade de ordem geométrica ou estática, substituindo procedimentos empíricos por uma metodologia racional de projeto. Para tornar a concepção do modelo menos dependente da experiência do projetista, o presente artigo tem como objetivo aliar a técnica de otimização topológica ESO (Evolutionary Structural Optimization) ao Método dos Elementos Finitos para geração automática dos modelos de bielas e tirantes. O critério de evolução do método de otimização topológica adotado considera a eliminação de elementos menos solicitados em termos de tensão, a partir de uma análise elástico-linear. Nesse contexto, é possível obter soluções otimizadas de problemas complexos envolvendo o concreto estrutural. São apresentados três exemplos numéricos para comprovação e validação das formulações e técnicas implementadas, cujos modelos de bielas e tirantes obtidos apresentam boa concordância em relação às respostas encontradas em trabalhos científicos precursores sobre o tema.
Nonlinear numerical analysis of prestressed concrete beams and slabs.
(2020) Silva, Amilton Rodrigues da; Rosa, João Paulo de Souza
Due to the development of new constructive techniques, design of structures in prestressed concrete has been widely used in the practice. In this work the plate, bar and interface finite element formulations for numerical simulation of prestressed concrete beams and slabs is presented. Emphasis is given on the interface element that has the function of simulating a possible slip between the concrete and the prestress tendon as well as the stress and strain in that tendon. This interface element together with the proposed numerical model are the main contributions of this work. Some numerical and experimental examples obtained from the literature are used to validate the proposed model. In the numerical analysis presented in this article the concrete slabs are modeled with rectangular plate elements and the concrete beams modeled with bar elements. The active reinforcement and the contact between the active reinforcement and the concrete are modeled by interface elements. The geometric and material non-linearity are considered in the numerical analysis. The examples analyzed show the efficiency of the proposed model.
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 das
New 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.
Numerical analysis of the effect of partial interaction in the evaluation of the effective width of composite beams.
(2017) Silva, Amilton Rodrigues da; Dias, Luís Eduardo Silveira
Most of the engineering problems involving structural elements of steel-concrete composite beam type are approximations of the structural problem involving concrete plates connected by connectors to steel beams. Technical standards allow the replacement of the concrete plate element by a beam element by adopting a reduction in the width of the plate element known as effective width. The effective width is obtained, in most technical norms, taking into account only the parameters of beam span length and distance between adjacent beams. Numerical and experimental works found in the literature show that this effective width depends on several other parameters, such as the width and thickness of the concrete slab, and the type of loading. The objective of this work is to verify the influence of the partial interaction in the evaluation of the effective width of composite beams formed by a concrete slab connected to a steel beam with deformable connection, being used in numerical simulation three types of finite elements: a plate element for nonlinear analysis of the concrete slab; a bar element for non-linear analysis of beams with cross-section defined by a polygon; and an interface element which connects the plate and beam elements, simulating the deformation effect of the shear connectors. In the studied examples, it was found that the reduction of the shear connection stiffness at the interface between the concrete slab and the steel beam leads to a decrease in the shear lag effect and, consequently, makes the effective width of the concrete slab closer to the its real width. In another example, curves are constructed to define the effective width of a composite beam with medium stiffness. Considering maximum stresses and maximum displacements, these curves are obtained by forcing the equivalence of the approximate model with the model closest to the real problem.
Optimization of reinforced concrete polygonal sections under biaxial bending with axial force.
(2018) Silva, Amilton Rodrigues da; Faria, Flávia Castro de
Concrete is the world’s most utilized material for production of the structural elements employed in civil construction. Due to its low tensile strength and brittle nature it is reinforced with steel bars forming the reinforced concrete (RC structure). Linear elements of reinforced concrete are commonly employed in multi-story buildings, bridges, industrial sheds, among others. In this study an optimization algorithm is presented to define the amount of steel and its location within a concrete polygonal section subjected to biaxial bending with axial force, so that the amount of steel would be the minimum needed to resist the soliciting forces. Therefore, the project variables are: location, diameter and number of steel bars to be distributed within the concrete polygonal section. The sequential linear programming method is used to determine the optimized section. In this method, the non-linear problem of determining the resistance forces of the section in relation to the project variables is approximated by a sequence of linear problems, which would have its optimal point defined for each step using the Simplex method. Formulation validation is done through results of examples found in literature, and also by means of analytical solutions of simple problems, such as rectangular sections under axial force and moment in only one axis of symmetry. The results show the efficiency of the algorithm implemented in the optimized determination of the quantity and position of the bars of a given diameter in the polygonal section of reinforced concrete under biaxial bending with axial force.

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