Programa de Pós-graduação em Geotecnia, Estruturas e Construção Civil
URI Permanente desta comunidade
Navegar
Navegando Programa de Pós-graduação em Geotecnia, Estruturas e Construção Civil por Por Orientador "Araújo, Daniel de Lima"
Agora exibindo 1 - 8 de 8
Resultados por página
Opções de Ordenação
Item Ligações formadas pelo transpasse de armadura dobrada em forma de laço: análise da influência das fibras de aço(Universidade Federal de Goiás, 2011-07-11) Curado, Marina Craveiro; Araújo, Daniel de Lima; http://lattes.cnpq.br/8801080897723883; Araújo, Daniel de Lima; Almeida, Sylvia Regina Mesquita de; Giongo, José SamuelCurved anchorages shall be used once there is the need of reducing the necessary length for the transference of stresses between reinforcement and concrete. The transference of stresses in this case is performed not only through the bond between both materials but also through radial compression onto the concrete. Besides enhancing the bond properties between the reinforcement and the concrete, the addition of steel fibers to the concrete also enhances the strength to material tension contributing to avoid the splitting within the loop level. This paper aims at studying connections resistant to normal tension force composed by the overlapping of bent bars into loop shape. In order to do so, an experimental program was developed to evaluate the influence of some variables in the anchorage strength and connections formed by bent bars into loop shape. In both cases, the bending diameter of the loop and the grade of steel fibers added to the concrete were adopted as variables. Different development lengths regarding the pullout experimental data were also considered in order to assess anchorage strength. The influence over connection strength of the transversal reinforcement presence to the loop level was also analyzed. The outcomes of experimental data showed that the adopted bending diameter to the loop have influenced neither anchorage strength nor connections. Anchorage strength is related to the development length of the reinforcement within the concrete. Once 2% of steel fibers were added to the concrete, there was yielding of the reinforcement into a development length of only 50 mm. Regarding the connections, the presence of transversal reinforcement ensured a gradual loss of force within the post-peak section. Such reinforcement only influenced the connection strength when it was used together with 1% steel fibers. The fibers provided additions to the anchorage strengths and to the connections allowing the length reduction of anchorage loops. The strut and tie model was employed within the development of one expression to the calculation of the studied connection strength. Overall, the proposed equation tended to underestimate the values of maximum force.Item Estudo dos mecanismos de transferência de tensões de cisalhamento em concreto reforçado com fibras de aço: análise do intertravamento de agregados(Universidade Federal de Goiás, 2017-06-30) Lobo, Fausto Arantes; Araújo, Daniel de Lima; http://lattes.cnpq.br/8801080897723883; Araújo, Daniel de Lima; Pituba, José Julio de Cerqueira; Bittencourt, Túlio NogueiraIt was performed an experimental analysis in order to evaluate the contribution of the steel fibers and the aggregate size in the shear strength of the concrete. This paper describes tests to evaluate the shear strength and a test method for evaluation of shear stress transfer by aggregates interlock. In the experimental development, it was used concrete with a mean strength of 60 MPa, with 9.50 mm and 12.50 mm coarse aggregate, varying the volume of steel fibers in 0%, 0.5% and 1.5%. The results showed that the methodology developed to evaluate the direct shear test with two planes worked well until the maximum force for all the models. The direct shear testing results for pre-cracked (push-off test) attested that the fibers contribute to the effect of the aggregates interlock by reducing the crack opening and the sliding of the interface for a given shear stress. Moreover, the aggregate size contributes to the increasing of the interface roughness and consequently in the increasing of shear stress transfer. In addition, it was proposed the modification in one of the empirical models used to evaluate the interlocking aggregate phenomenon in the concrete by considering the experimental value of shear strength concrete. This modified empirical model demonstrated good correlation with the shear stress versus dilatancy that was obtained experimentally.Item Estudo dos mecanismos de transferência de tensões de cisalhamento em concreto fissurado com e sem reforço de fibras de aço: uma análise exploratória(Universidade Federal de Goiás, 2016-07-28) Martins, Bárbara Gomes; Haach, Vladimir Guilherme; http://lattes.cnpq.br/8295425848418855; Araújo, Daniel de Lima; http://lattes.cnpq.br/8801080897723883; Araújo, Daniel de Lima; Pituba, José Júlio de Cerqueira; Lima, Maria Cristina Vidigal deThe steel fiber-reinforced concrete have been widely used in concrete pieces to improve their mechanical properties. This research is performed an exploratory experimental analysis in order to assess the contribution of steel fibers in the shear strength of the concrete. A methodology for evaluation of the direct shear strength and the direct tension of the concrete is developed, as well as to evaluate the shear stress transfer mechanism by aggregate interlock. From the tests, it evaluates the influence of steel fibers in the transfer mechanism of shear stresses through the aggregate interlock pre-cracked plans of concrete. In the experimental development was used medium strength concrete (60 MPa), with 12.5 mm coarse aggregate varying the volume of steel fibers in 0%, 0.5% and 1.5%. The results showed that the methodology developed to evaluate the resistance to direct tensile work, but there needs some modification in the molding of concrete specimens with fibers to prevent the concentration of fibers in the specimen faces, which resulted in reducing the tensile strength of concrete. As for the direct shear test with two planes, the results showed that the test methodology worked well until the maximum force, showing a reduction in the shear strength of the concrete when compared to similar tests, but with fixed supports. Finally, the results of direct shear testing on pre-cracked (push-off test) showed that the fibers contribute significantly to the effect of aggregate interlock by reducing the opening of the crack and the sliding interface for a given shear stress.Item Análise do conforto ambiental em salas de aula da Universidade Federal de Goiás(Universidade Federal de Goiás, 2010-09-24) Ochoa, Juliana Herlemann; Araújo, Daniel de Lima; http://lattes.cnpq.br/8801080897723883; Brandstetter, Maria Carolina Gomes de Oliveira; Sattler, Miguel Aloysio; Morais, Ludmila Rodrigues deProvide users good physical conditions in educational institutions is essential for the proper development of teaching and learning. This work deals with the verification in-loco of the environmental comfort of classrooms in two buildings with different architectural and construction techniques, that are part of the structure of the Federal University of Goiás. So the research aimed at exploring these buildings in order to identify the peculiarities of its thermal, acoustic and light performance which are being influenced by the technologies adopted and the physical conformation of the same. The technical data collected were analyzed by type of comfort. In lighting comfort, measurements were carried out near the solstices and equinoxes and the data collected were analyzed by means of ambient illuminance, uniformity coefficient and contribution of artificial light. The thermal comfort data collected were temperature and relative humidity for a period of approximately 11 months, which were assessed using the concept of comfort zone, degree-hours analysis and absolute maximum and minimum values. The acoustic measurements collected the sound pressure levels and occurred over a day of daily activities in both buildings. It was noted that there is an influence of the architectural elements of environmental comfort in buildings. Among other factors, one that can be highlighted is that despite having similar solar orientation, which is a comfort condition, the results of the environmental performance of each of the buildings were quite different. Parallel to these technical assessments were also done a periodic application of questionnaires to the users of the classroom, one per season, which sought to characterize the perception of these in relation to each of the types of comfort. Finally, a correlation was established between the technical data collected and perceptive. In most of cases, the opinions expressed by users were not consistent with the results evaluated by measurement techniques, thus demonstrating a difference between the comfort zone adopted and the actual user satisfaction of the buildings.Item Consolos de concreto moldados em duas etapas: influência do tratamento da interface e da adição de fibras de aço(Universidade Federal de Goiás, 2012-08-29) Oliveira, Edilene Muniz de; Araújo, Daniel de Lima; http://lattes.cnpq.br/8801080897723883; Araújo, Daniel de Lima; Almeida, Sylvia Regina Mesquita de; Debs, Mounir Khalil ElConcrete corbels are among the most used components to connect precast elements. Series production is often prejudiced by the necessity of making corbels in different positions in precast elements. To reduce this obstacle and rationalize the production, execution of concrete corbels cast in two stages can be a good alternative. The researche reported here intended to evaluate different procedures of making concrete corbels cast in two stages, being column cast firstly and, after removing formwork, corbels can be cast. Concrete corbels with and without steel fibers, both with horizontal stirrups and with steel fibers replacing it, with varying the treatment of joint and the shape of the connect the main steel bars to the column were analyzed. To do so, experimental and analytical analyses of concrete corbels cast monolithically and in two distinct phases were carried out. In the tests, the strength, vertical and horizontal displacements in relation to the column, the opening of cracks and strains of main steel and horizontal stirrups were determined. From these tests it was observed that the ultimate strength of monolithic corbels increased significantly when steel fibers were added to concrete, even when they replaced the horizontal stirrups, but this increase did not occur in concrete corbels cast in two stages. However, it was observed that steel fibers could replace the horizontal stirrups without damage to the bearing capacity. Besides, the presence of horizontal stirrups increased the ultimate strength of the concrete corbels without steel fibers cast in two stages. It was also observed that the opening of the joint between the corbel and the column was also influenced by the presence of horizontal stirrups for concrete corbels cast in two stages and monolithic concrete corbels. In the other hand, steel fibers added to the concrete did not affect the opening of the joint corbel-column of corbel cast in two stages, but substantially reduced this opening in monolithic corbels. Finally, it was observed that the treatment of the interface had little significance in the ultimate strength of the concrete corbels cast in two stages, but it influenced the opening of this interface, although only in concrete corbels with horizontal stirrups.Item Análise numérica de estruturas de concreto com fibras utilizando mecânico do dano(Universidade Federal de Goiás, 2014-08-21) Pereira Júnior, Wanderlei Malaquias; Pituba, José Júlio de Cerqueira; http://lattes.cnpq.br/6503462610408968; Araújo, Daniel de Lima; Pituba, José Julio de Cerqueira; Almeida, Sylvia Regina Mesquita de; Vanderlei, Romel DiasThe work is a contribution to the mechanical numerical modeling of concrete structures with steel fibers using constitutive models based on Damage Mechanics behavior. The same, presents the formulation of a model proposed Damage admits that the concrete as initially isotropic elastic material, but with the evolution of the damage process, the material exhibits plastic deformations, anisotropy and bimodularidad induced damage. The incorporation of fibers in the modeling is performed through a homogenization procedure. The constitutive model for the concrete as well as the homogenization technique for dealing with the case of fiber concrete are implemented on a structural analysis program bar finite element laminated in layers. The parametric identification of the constitutive model together with the proposed homogenization is carried out using experimental results from the literature. Finally, numerical analysis of reinforced concrete beams reinforced with steel fibers and subjected to bending are conducted to assess the applicability of the constitutive model considered in this work. An attempt is thus contribute to the study of the deformation of fibrous concrete beams in service, in order to aggregate results and discussions in a future proposal of Brazilian technical standard for this type of structure.Item Ligação viga-pilar em fase de montagem para estruturas de concreto pré-moldado: análise via modelagem computacional(Universidade Federal de Goiás, 2016-07-05) Silva, Erlucivânia Bueno da; Araújo, Daniel de Lima; http://lattes.cnpq.br/8801080897723883; Araújo, Daniel de Lima; Soares, Renata Machado; Oliveira Júnior, Luiz Álvaro deThe connection is one of the most important phases in the precast structures project, being responsible for connecting the elements and enabling the efforts transference, directly interfering on the global stability of the structure. The real connection behavior can be studied by using physical experiments or by computer modelling. Both must be confronted with analytical models in order to obtain models that can be employed in the project connections. The computer modelling is a practical and economical way to investigate the structures behavior due to the programs sophistication based on the Finite Element and of Contour Method, and thanks to the increasing processing of computers performance. This study aims to analyze, by computer modelling, using the program DIANA® 9.6., the behavior of a beam-column connection composed by a steel corbel, formed by welded steel sheets “U” shaped, inserted in the column, and a steel hanger, inserted in the beam, formed by welded steel sheets in the shape of rectangular and hollow profile section. This connection has been studied experimentally by Prado (2014). The computer results of the validated three-dimensional model are compared with experimental ones and with the calculating models. In the final part, new proposals with modifications in the union form between the elements are presented in order to improve the mechanical performance. It was observed that the ultimate strength in proposals I and II, were respectively, 5,19% and 17,17% greater than the one in in the computer model M-VIIc.Item Avaliação da resistência à força cortante de lajes alveolares protendidas em piso misto de altura reduzida por meio de modelagem computacional(Universidade Federal de Goiás, 2021-07-01) Souza, Jefferson Rosa de; Araújo, Daniel de Lima; http://lattes.cnpq.br/8801080897723883; Araújo, Daniel de Lima; Almeida, Sylvia Regina Mesquita de; Nardin, Silvana deTo be a competitive solution as a structural system, since both elements are industrialized, reaching efficiency from a structural and constructive point of view. In a conventional composite floor system, the slabs are supported on the top flange of the steel profile and the composite action between the materials is guaranteed by mechanical connection. In a shallow composite floor system (slim floor), the slabs are supported on the bottom flange of the steel profile, which is incorporated into the height of the slab. In this case, the composite action can be guaranteed by mechanisms of adhesion between the materials, by means of concrete pins, reinforcement bars passed in the web of the steel profile or shear connectors. Slim floor system presents various advantages with respect to the conventional composite floor, such as greater protection of the metal profiles against fire and, especially, a reduction of the beam and slab set height. However, during the design phase, the shear strength of hollow core slabs on flexible supports needs particular attention and caution. In this context, this study aims at investigating the mechanical behavior of slim floors, focusing on the shear strength of hollow core slabs supported on steel profiles, through computational modeling via the Finite Element Method. To calibrate the computational models, test results on physical models available in the literature have been used. Numerical simulations of isolated hollow core slabs supported on rigid support and slim floor systems were compared with experimental test results, and analytical models for prediction of the resistant shear force. The computational models well-reproduced the tests of slim floor systems with hollow core slabs. A parametric analysis was carried out to evaluate the influence of the core filling of the slabs and the variation of flexural stiffness of the steel profile. The results of the parametric analysis indicate that the shear strength is marginally affected by the filling of the cores. In the case of the use of slabs with oblong-shaped openings, the filling can reduce the shear strength of the slab. The influence of support flexibility on the shear strength of the slab was well represented by an analytical model available in the literature, providing better strength prediction than the model recommended in technical bulletins published by fib (International Federation for Structural Concrete).