Navegando por Assunto "INFRAESTRUTURA"

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Acesso aberto (Open Access)
Análise comparativa das sensibilidades obtidas com o vane test e o mini vane em um depósito sedimentar na foz do rio Amazonas
(Universidade Federal do Pará, 2022-11-22) VIEIRA FILHO, Arudá Gomes; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
The reed test has been used in field research for the elaboration of geotechnical projects and in the management of non-clay sedimentary deposits, due to the fact that it provides data such as undrained shear strength (Su) and sensitivity (St). The same results are obtained in the test with the laboratory straw (mini vane), but for that, it is necessary to extract samples considered undisturbed, which, in this research, were recommended by the ABNT NBR 9820 standard. vane shear test with the laboratory vane test, also called Mini Vane. The location of this analysis is in a port region located at the mouth of the Amazon River, in a natural sedimentary deposit, which presented two slope disruptions with characteristics peculiar to soils with high sensitivity. Landslides on slopes are usually predictable from a geotechnical point of view, however in this researched region the soil presented rapid landslides on the slope, showing signs of a soil with high sensitivity. The research pointed out that the laboratory vane test (mini vane) presented a greater (St) when correlated with the (St) of the simple compression tests, giving greater clarity that there is a very soft clayey soil with a depth between 30 and 40 meters, typical of a ground lens that performed with high sensitivity. Comparisons between the reed tests showed consistency in the results, even in soil layers with different consistency indices than the initial layers, the validations of the reed tests were validated with the tests performed by simple compression. Finally, the soil of this deposit had its sensitivity identified in the field straw test. The same identification was confirmed on the Mini Vane. However, at depths greater than the field vane. In this way, the tests carried out by the Vane Shear Test (VST) in situ were primordial in the identification of the sensitivity, having its confirmation with the laboratory reed test (Mini Vane).
Acesso aberto (Open Access)
Análise da viabilidade técnico-econômica de implantação de reciclagem de pneus para produção de CBUQ em Tucuruí
(Universidade Federal do Pará, 2019-02-21) MOUSINHO, Mateus Mamede; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
Population growth and rapid technological development have contributed to increased solid waste generation by improperly disposing of post-consumer tires, which are not biodegradable and their decomposition time is not yet precisely determined. To be defended that the recycling culture does not only show aspects of environmental and educational preservation, it is also necessary to justify recycling as an economic activity that generates employment and income to the city, contributing to the well-being and quality of life. Therefore, the main objective of this research was to quantify the discard of waste tires and to analyze the technical-economical feasibility for the implementation of the recycling process of waste tires in the production of rubber aggregate in the asphalt mixture at the city's asphalt plant. To do so, it was measured the disposal of waste tires in a given period in Tucuruí and estimated the disposal volume of the adjacent cities, in addition, it was analyzed the operational activities and production costs of the waste as a rubber aggregate. In the field survey, 98 questionnaires were applied in 30 neighborhoods where the establishments were in January 2018. Thus, there was a monthly amount of 1,664 tires in the rubber workshops, 2,347 tires in the mechanical stores, totaling 4,011 tires in the municipality, which allows to conclude that the city presents a large volume of this solid residue. Adjacent cities presented in their estimate a total of 8,031 tires unserviceable per month. For the production of the rubber aggregate asphalt mixture, the conventional CBUQ trait was used in relation to the modified CBUQ developed by Coelho (2018), in which it was estimated that one kilometer of asphalt mixture of thickness of 3,5 centimeters can be used approximately 11.72 tonnes of recycled aggregate (8.79 tonnes of rubber and 2.93 tonnes of wood sawdust), this is equivalent to 1,465 car tires or 5,170 motorcycle tires, leading to an economy in the purchase of raw material from R$ 56,075.41 per kilometer. It is concluded that the results of the three scenarios are satisfactory, the simulations of the study were only the resources available to produce the rubber aggregate generated by the municipality as a pioneer project, with the intention that other municipalities are part of this visual identity of sustainable city.
Acesso aberto (Open Access)
Análise da vida útil e o custo de reparo de fachadas de edificações verticais
(Universidade Federal do Pará, 2020-02-28) VELOSO, Thiago Pinheiro; MAUÉS, Luiz Maurício Furtado; http://lattes.cnpq.br/7497951647889934; https://orcid.org/0000-0002-1762-8617
The façades of buildings have frequently presented levels of degradation higher than desired in recent years, exposing problems related to quality and durability, characterized by premature aging due, above all, to the appearance of pathological manifestation. Such complications cause several problems, affecting use, aesthetics, safety, and above all the durability of the buildings. With the advent of the Performance Standard (ABNT, 2013), it was possible to create durability parameters for all elements of a building, from the definition of durability terms in three levels: minimum, medium and maximum. In this sense, we sought to evaluate the usefull life of vertical building facades, as well as the frequency with which intervention occurs is them, the cost of repair, as well as a simulation was performed in the software “simulates v 4.4”. From the data collection with the application of a form in a company of great representation in the sector of façade repair, it was possible to account for 40 buildings with signs of dregacy. These buildings were divided into two groups taking into account the intervention time after delivery, that is, a group comprised between 1 and 7 years and another group between 8 and 15 years. With the adoption of the “simula v 4.4” software, based on the Monte Carlo method, cost and time simulations were carried out, aiming to determine the number of interventions required to manintain these facades, as well as the cost for such, in a cycle of 50 years. The results presented show that Group I had a lower performance than Group II in both situations, requiring more repair actions and a higher execution value, considering a minimum, medium and maximum reference generated by the program. In addition, the figures obtained show that both groups are below the minimum durability term recommended by the standard, which is 20 years, beyond the average and maximum terms, which are 25 and 30 years respectively, confirming the presence of a series of factors that interfered in the process of design and execution of the these facades. Thus, it is concluded that special attention should be given in the assembly of the facades of the buildings, as they are a very expensive component of the work, and that add a lot of value to the final product.
Acesso aberto (Open Access)
Análise das propriedades tecnológicas da cinza do caroço de açaí na cerâmica vermelha
(Universidade Federal do Pará, 2019-09-16) FERREIRA, Taiana da Silva; SOUZA, Paulo Sérgio Lima; http://lattes.cnpq.br/4933212993218783; ISHIHARA, Júnior Hiroyuki; http://lattes.cnpq.br/3498874642887006; https://orcid.org/0000-0002-0081-7913
The raw materials from the exploration of deposits used for the manufacture of products used in construction and the environmental impacts caused by the red ceramic sector evolved as cities developed. The need for the use of alternative materials, such as waste biomass, has become increasingly necessary studies aimed at the reuse of waste in the process of production and manufacture of ceramic materials. Thus, this work has the objective of evaluating the incorporation of ash from the acai kernel residue (RCA) in the clay mass and to evaluate the technological properties of red ceramic. The materials were chemically and physically characterized, and then extruded specimens were molded using 0%, 10%, 15% and 20% RCA ash mixed in two types of clay, called red clay and dark clay. After firing at 950 ºC, the pieces were subjected to water absorption, apparent porosity, specific gravity, linear shrinkage and flexural strength stress tests. The results showed that the use of RCA ash contributed to the workability of the mixtures, reducing the need for additional water for molding. It was also verified that the 10% ash content as a partial substitute of red clay, and the mass containing 50% of red clay and 50% of dark clay, had a positive influence on the evaluated technological properties. However, for the 20% ash incorporation of RCA, the values were median and for the unsatisfactory porosity assay. Thus, it was possible to verify the technical feasibility of using açaí stone ash in partial substitutions, contributing to the reduction of raw material exploration, reduction of solid waste disposal and the reuse of the residual biomass of açaí stone in the production of ceramic materials.
Acesso aberto (Open Access)
Análise de atributos de classificação para o diagnóstico de falhas em rolamentos baseado em SVM
(Universidade Federal do Pará, 2019-08-06) SOUZA, Jusley da Silva; BAYMA, Rafael Suzuki; http://lattes.cnpq.br/6240525080111166; MESQUITA, Alexandre Luiz Amarante; http://lattes.cnpq.br/3605920981600245; https://orcid.org/0000-0001-5605-8381
In industries, the concern in total availability of machines and the mechanical equipment in the productive area it’s subject of research and tests to obtain more efficient techniques to be applied for monitoring and faults’ diagnosing. Bearings are machine elements of great application in the industrial area and they present high fault index that generate machine’s stops to carry out maintenance. For this reason, this paper presents Artificial Intelligence technique applied to the vibration signals of a rotary machine for fault diagnosis in its bearings. The vibration signals are part of an open database offered by Case Western Reserve University. In this paper the Support Vector Machine (SVM) classification algorithm is applied in two ways for the rolling bearings faults’ diagnosis. In the first case statistical predictors (Root Mean Square Value, Crest Factor, K Factor, Kurtosis and Skewness) are used as features for the SVM classifier. In the second case, the signal processing is performed by applying the Ensemble Empirical Mode Decomposition (EEMD), which generates several signals called Intrinsic Mode Functions (IMFs). For each IMF, it’s modeled using Autoregressive Modeling (AR), and the AR modeling coefficients of each IMF are used as features for the SVM classifier. The analyzes are performed for training and validation groups, with randomly chosen window and with temporal sequence chosen window, considering two classification problems within the same data, the first one considers the same severity and only changes the fault type and the other vary both severity and fault type. As result, both methodologies presented excellent reliability results for bearing faults’ diagnosis.
Acesso aberto (Open Access)
Análise de dano em barragens de concreto através do método dos elementos finitos
(Universidade Federal do Pará, 2019-08-30) BORGES NETO, Osvaldo Sousa; PRAZERES, Plínio Glauber Carvalho dos; http://lattes.cnpq.br/6175760351403329
The mechanics of damage in continuous mediums studies the effects of degradation, in diffuse and progressive way, suffered by solid bodies under requests of mechanical or non-mechanical nature. Therein such effects are taken into account by reducing the strength and stiffness properties of the damaging material. Materials such as concrete and rocks have as their basic reason for their nonlinear behavior, micro defects in their microstructure that favor the concentration of micro tensions. These micro defects constitute what is understood as the initial damage of the material. The purpose of this work is the study of appropriate damage models for the analysis of damage mechanisms in concrete dams. For this, a linear softening isotropic damage model was used and the damage model of Cervera et al. (1996) in the analysis of two sections of concrete dams. The model of Cervera et al. (1996) stood out for presenting good results in the identification of damage as well as better describing the real aspect of the stress versus strain curve of the concrete. To validate the results, the example of a wall beam by Proença et al. (2002) in which the damage results were compatible with that of the Matlab language program.
Acesso aberto (Open Access)
Análise do comportamento de 3 pontes mistas em obras rodoviárias sujeitas à prova de carga estática
(Universidade Federal do Pará, 2023-03-01) SILVA, Paulo Roberto Fontes da; PEREIRA FILHO, Manoel José Mangabeira; http://lattes.cnpq.br/4765401390604065; https://orcid.org/0000-0001-9622-3863; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
Along the BR 230/PA, some bridges had their constructions interrupted about 20 years ago, and with the purpose of providing evaluation criteria to the works of road bridges with mixed structure in steel and concrete is proposed the methodology above. As acceptance criteria, static load tests were used in road bridges with mixed structure through characteristic tests, through instrumentation using strain gauges and LVDT's (Linear Variable Differential Transformer), defining displacements and deformations in the structural elements of the OAE (Special Artwork Bridge), with subsequent computational modeling of the structural model of the bridge, aiming to evaluate the performance of the bridges in service, as established in the structural modeling to the core of the OAE project, which were sized for a type train TB-45 (Type Vehicle of 450 kN of total weight),, according to NBR 7188 (2013). To monitor the displacements, LVDT's were used, positioned in the middle of the span and 1/4 of the span of the central stringers, as well as the strain gage allocated in the steel beams, brace and in the CA-50 steel bars of the pillars with verification of the deformations of the referenced structural parts. As results, an evaluation of the service conditions of the bridge was performed, compressing the experimental results of the static load tests with the theoretical-computational predictions in order to validate the models used, in general, the experimentally observed deformations were less intense than the theoretical estimates. This fact corroborates the agreement with the greater rigidity of the structural elements, validating the experimental results, because they presented behavior similar to the theoretical one, however in lower intensity of the OAE's studied. Thus, the experimental and theoric-computational results were compared with the international norms being the ratios of maximum displacement, residual displacement and deformation. The experimental response showed similar behavior, for the bridges over the Arataú, Anapú and Poraquê rivers, to the theoretically predicted. Inaddition to international norms, the results were divergent, especially in the Turkish, Spanish and German countries, and the boundary conditions imposed on the norms should be imposed.
Acesso aberto (Open Access)
Análise experimental da eficiência de bielas de concreto simples e armado em modelos locais e globais
(Universidade Federal do Pará, 2019-03-21) FREIRE, Marília Caires; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479
Reinforced concrete beams are usually designed by sectional analysis methods, where Bernoulli hypothesis is taken into account, assuming that strains are linearly distributed along the cross-sectional area of the element. However, many practical situations require distinct calculation alternatives, made by both fundamentally empirical code expressions and numerical or analytical solutions from the Strut-and-Tie Method. This is the case of deep beams, where a bottle-shaped strut is formed and the influence of its reinforcement ratio is generally discounted by the current design codes. Therefore, an experimental study was performed to assess the efficiency of plain and reinforced concrete struts, by local and global models, respectively represented by diamond-shape panels loaded in small bearing areas and deep beams, since in both the resistant mechanism seems to be directly related to the flow of stresses in the concrete strut. The results showed similar behaviors among the models regarding strains in concrete and reinforcement, as well as equivalent failure modes resulting from a splitting crack of the strut. With the increase of transverse reinforcement ratio, gains of ultimate strength, ductility and cracking control were observed, mainly for specimens with mesh reinforcement, as well as higher and safe results for the analysis by the strut efficiency factors. On the other hand, the assessment of shear strength by the design codes showed unconservative predictions with increasing transverse reinforcement. This way, it is confirmed that solutions by strut-and-tie models are more suitable methods for the efficient and safe design of structures with regions of disturbance in the stress-strain distribution.
Acesso aberto (Open Access)
Análise experimental da influência da adição de fibras e da variação da armadura de costura em consolos curtos de concreto armado
(Universidade Federal do Pará, 2022-06-23) BRANDÃO, Jaciara Santos; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
Reinforced concrete corbels are usually characterized by being support elements whose design can be made from the Strut-and-Tie Method (STM) which is based on fundamental assumptions that consider that the tensile stresses are absorbed by the rods (structural steel) and the compressive forces are absorbed by the struts that are formed inside the concrete section, as it is understood that these elements have regions of discontinuity (D) or disturbances in the stress distribution. This method can be applied in the case of short corbels as they also present regions (D), given that their stress flow occurs in a non-linear manner. In this way, this experimental study analyzed the influence of the addition of synthetic fibers (polyethylene and polypropylene) and steel in the composition of the concrete, as well as, to verify the influence of the variation of the seam reinforcement rate in order to validate the MTB as a solution safe and efficient for the design of elements that present discontinuities (D) or disturbances. In the tests, the breaking load, the opening of cracks and the deformations in the tie rods, seam reinforcement and in the concrete, internally and externally, were observed. The results showed that the specimens containing synthetic fibers showed the highest strengths compared to the steel fiber specimen, being on average 10.82% more resistant than the reference specimens, despite not containing the highest fiber contents. In general, the elements showed similar ductile behavior and failure mode, so the cracks occurred in a controlled manner and there was no sudden rupture. As for the deformations in steel and concrete, the results showed a similar behavior among the specimens.
Acesso aberto (Open Access)
Análise experimental da influência de ancoragens e taxas de armadura na resistência à flexão de consolos longos reforçados com laminados de fibra de carbono
(Universidade Federal do Pará, 2025-05-29) SILVA, Lucas Carvalho; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
For the repair and strengthening of reinforced concrete corbels, solutions are sought that extend the service life of these structures, increase their load-bearing capacity, reduce deformations, and limit crack propagation. Therefore, this study presents tests on experimental models of corbels strengthened with Carbon Fiber Reinforced Polymer (CFRP) laminates to analyze the strength enhancement in these models. All corbels are chamfered and have the same geometry. Thus, the ratio between the load application point (a) and the effective depth (d) is approximately 1.28, allowing the behavior to be characteristic of either a corbel or a cantilever beam. All specimens have a geometric arrangement with 250 mm width, 400 mm embedded height, 200 mm height at the outer face, and 570 mm length. The main objective of this research is to analyze the behavior of the reinforcement according to the variation in the main reinforcement ratio and the anchorage method, to compare the experimental results with current standards, and to verify whether the proposed anchorage systems prevent premature failure modes. The reinforcement dimensions consist of a (50x1440) mm laminate applied to both faces of the corbel. Two configurations of the anchorage system were analyzed. The first anchorage method involves attaching bolts through plates that do not perforate the laminate, known as Hybrid Bonding (HB). The second method, classified as FT (based on the laminate application approach), uses the reinforcement laminates themselves, with overlapping layers — the final one being applied perpendicular to the reinforcement and previous layers. Regarding the results, it was observed that both anchorage methods are effective in increasing the strength of the specimens, with HB being the most suitable anchorage method. Furthermore, depending on the reinforcement ratio, the strength gains provided by the reinforcement vary, being less effective in corbels with higher main reinforcement ratios. Finally, it was noted that the proposed anchorage methods were not entirely effective in preventing debonding along the laminate. However, it is worth highlighting that in the corbels with HB anchorage, even with reinforcement debonding, the anchorage was able to prevent complete slippage, contributing to increased ductility of the corbel even after debonding.
Acesso aberto (Open Access)
Análise experimental da resistência à punção em lajes lisas com substituição de agregados graúdos naturais por reciclados de concreto
(Universidade Federal do Pará, 2022-05-12) RIBEIRO JUNIOR, Jayron Alves; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479
The popularization of the use of recycled concrete aggregates has increased due to socioeconomic aspects, but above all, as sustainability is being pursued and, in this context, some international standards have been published to facilitate and standardize the use of this material. Despite the constant evolution of studies on punching shear, there is a need for national and international regulatory adjustments in relation to the use of recycled concrete aggregates in flat reinforced concrete slabs. Two reasons explain the slight influence of the incorporation of recycled aggregates on the punching shear resistance of concrete slabs: lower mechanical strength and better bond between the cement paste and the recycled concrete aggregate due to the higher cement content, porosity, and roughness, when compared with natural aggregate. Thus, the punching shear strength is influenced by these properties of the aggregates along the shear plane of the cracks, the two effects offset each other, leading to a similar punching shear strength. This research carried out the experimental test of 6 flat slabs of reinforced concrete without shear reinforcement subjected to symmetrical loading, containing variations in the rate of flexural combat reinforcement (0.7% and 1.4%) and replacement rate of natural aggregate by recycled concrete aggregate (0%, 30% and 100%). The study evaluated the influence of these variables on the punching shear resistant capacity and analyzed the upper limits of resistance. The slabs were octagonal with 2500 mm of distance between parallel faces, sides of 1030 mm and thickness of 210 mm, molded with concrete with fck of 25 MPa and supported on columns of 300 mm of side. The standards used as a parameter for estimating resistant capacity were NBR 6118:2014, ACI 318:2019 and Eurocode 2:2004. The experimental results showed that the slabs with ARCO showed a maximum reduction of 6 % in the punching shear resistance when compared to the slabs with conventional coarse aggregates. The reinforcement rate was able to increase the cracking load at the service limit state (ELS) and the recycled concrete aggregate had little influence on the opening of cracks in the slabs with the highest rate of flexural reinforcement.
Acesso aberto (Open Access)
Análise experimental de consolos curtos de concreto armado com fibras e variação da armadura de costura
(Universidade Federal do Pará, 2023-11-23) QUEIROZ, Daniel Pessanha de; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
Short armoured concrete consoles are pre-molded structural elements, arranged in balance, which function as a load support. This work aims to analyze experimentally the behavior of short consoles of armed concrete with variation of sewing armour area and application of a fixed content for steel fibers, polyethylene and polypropylene. Ten symmetrical specimens were analyzed, where four speciments did not contain sewing armor and possessed respectively the steel fibers (CA), polyethylene (CPE), polypropylene (CPP) and a fiber-free (CSF). Four specimens with six sewing armor Ø6.3 mm and used steel fibres respectively (C6Ø6.3A), polyethylene (C6Ø6.3PE), polypropylene (C6Ø6.3PP) and a fiber-free (C6Ø6.3SF). One specimen with six armor Ø5.0 mm seam and polyethylene fiber (C6Ø5.0PE). One specimen with eight armor Ø5.0 mm seam with polyethylene fiber (C8Ø5.0PE). They are presented, analyzed and discussed the results of: deformations of concrete and main traction armor and sewing; breaking modes; cracking maps and patterns; end resistance and loads of consoles; as well as the efficiency factors of biela, subsequently these topics above should be compared with those obtained by Abrantes (2019) and with what advocates the regulatory standards ABNT NBR 9062 (2017), NBR 6118 (2023), EUROCODE 2 (2010) and ACI 318 (2014). It is concluded that they have achieved better results compounds that received the addition of fibers. In terms of compression, traction and modulus of elasticity, comparing the matrix without and with fibres, polyethylene was 15%, steel 18% and polypropylene 21% more efficient, respectively. It can be seen that for each test a different fibre performed better. In general, C8Ø5.0PE achieved good results in all analyses, despite not being the specimen with the largest seam reinforcement area. This result is justified by the arrangement of the reinforcement inside the concrete, as well as the presence of the polyethylene fibre.
Acesso aberto (Open Access)
Análise experimental de consolos curtos de concreto com armaduras continuas e descontinuas
(Universidade Federal do Pará, 2019-09-30) ABRANTES, Jedson Henryque Corrêa; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
Short consoles, as well as some reinforced concrete elements, have discontinuity regions (D regions), where Bernoulli's hypotheses should not be taken into account, since stress flows do not distribute linearly along the cross section. In order to correct the disturbances caused by this flow in specific areas, it is necessary to look for alternatives of calculation through equations idealized by empirical perceptions of researchers, or by means of the Strut-and-Tie Method. In this context and after theoretical and experimental observations of consoles, it was concluded that it is formed in this structure a bottle-shaped strut, and although there is a considerable database in this regard, there is no consensus in the literature and among current codes that relate between continuous reinforcement rates, failure mode and strut efficiency factors . Thus, an experimental study was carried out to evaluate the contribution of three types of fibers (discontinuous reinforcement), polypropylene, polyethylene and steel, which were added to the concrete in three different contents for each one. The results showed that in general there were similar behaviors for the concrete readings, and the opposite when analyzing the continuous reinforcement that suffered tensile stresses (Tie). For the elements with metallic fibers the resistance gain in relation to the reference specimens was noticed for the part that received higher fiber content. For synthetic fibers, polypropylene fiber had better gain in the specimen with second best fiber volume, and for polyethylene was registered for the lowest percentage. These consoles also presented better ductile behavior among all the test elements that did not receive horizontal stirrups. Regarding the results compared to the specimen with continuous reinforcement only the one with polyethylene fiber achieved superior result. Regarding the strut efficiency factors, the method presented results against and in favor of safety, while with respect to the shear strength the codes estimates had very favorable results. Therefore, MBT is a very suitable method for design that presents efficiency and safety through structures that present stress and deformation disturbances.
Acesso aberto (Open Access)
Análise experimental de vigas de concreto armado reforçadas à força cortante com compósitos de fibra de juta, carbono e vidro utilizando a técnica EBR
(Universidade Federal do Pará, 2022-10-18) MACIEL, Luciana Pereira; BANNA, Wassim Raja El; http://lattes.cnpq.br/2005046563115507; https://orcid.org/0000-0001-5085-4352; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
The application of FRP (Fiber Reinforced Polymer) with the EBR (Externally Bonded Reinforcement) technique for repairing and reinforcing structures stands out due to the low density of the material and ease of application. In this case, the use of synthetic fibers is common, however, these fibers are considered inaccessible and harmful to the environment. This disadvantages raised studies on the replacement of synthetic fibers by natural fibers. Therefore, this work consists of the experimental analysis of the performance of composites of jute fibers as shear reinforcement. With that aim, seven reinforced concrete beams reinforced with FRP's were molded using the EBR technique, they were dimensioned with greater flexural strength in relation to the shear force and with transverse reinforcement positioned only in a section of the span, to induce shear failure in the region without stirrups. The beams are 2 meters long and have a cross section of (15x20) cm. One beam was not reinforced, to be used as a reference, one beam was reinforced with one layer of FRP with carbon fiber, one beam with two layers of FRP with glass fiber, two with hybrid FRP of layers of glass and jute fiber with three and four layers, and finally two beams with jute fiber FRP with two and three layers. The reinforcements were applied in strips along the length of the shear span of the elements, perpendicular to the axis of the beams, U-shaped. It was observed that the reinforcement with two layers of jute fiber presented a 48% increase in shear force of the beam in relation to the reference beam, this result was similar to that observed in the beam reinforced with one layer of carbon fiber. Other positive behaviors were observed in the other reinforced beams, such as cracking control, increase in maximum shear force and containment of vertical displacement in relation to the reference beam. The experimental results were compared to theoretical results calculated according to ABNT NBR 6118 (2004), ACI 318 (2014), Eurocode 2 (2004), ACI 440.2R (2017) and fib 90 (2019). After analysis, the initial results of this research demonstrate the viability for other in-depth studies on the use of jute fibers in shear reinforcement of reinforced concrete beams.
Acesso aberto (Open Access)
Análise experimental do cisalhamento em vigas de concreto armado reforçado com microfibras
(Universidade Federal do Pará, 2019-01-31) OLIVEIRA, Mateus Gonçalves de; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
The shear study for small, medium and large works, the latter known as works of art, with the use of reinforced or prestressed concrete presents particularities in the definitions of the traces, since, it has the need to minimize the propagation of fissures, as well as to obtain suitable mixtures considering the high characteristic high diameter of the large aggregates, as well as to avoid deleterious reactions in the concrete. In this sense, the main objective of this research is to analyze the shear behavior of reinforced concrete beams, with reinforcement of glass and polyester microfibers for each type of cited in volumetric fractions (0,024%, 0,032% e 0,048%), comparing them with the behavior of fiber- aiming its application in structural elements. In order to meet the proposal of this research, the methodology was based primarily on the characterization of concrete constituent materials (cement, small and large aggregates and fibers already mentioned), concrete dosage based on the Concrete Dosage method EPUSP -IPT, concrete of the beams, being: one of reference without fiber addition and 6 (six) with additions of microfiber of glass and polyester, being three (three) for each one of them, and later analysis as to shear through the breaking of the experimental beams, and computational analysis between the beam modeled in the Response 200 software considering stirrups throughout its section and the experimental reference without stirrups in 1/3 of its sections. It can be stated that the glass and polyester microfibers have shown that their uses can be used as partial replacement of the transverse reinforcement; contributed to post-peak or post-cracking stability; contributed to the gain in shear strength of 15.1% for VFV01 (beam with addition of glass microfibers with a percentage of 0.024%) and 21.6% of VFP02 (beam with addition of polyester microfiber with a percentage of 0.032%) both in relation to VR (reference beam). Therefore, this study demonstrated that the fibrous reinforcement can be used as control efficiency and as well as shear performance improvement in structural concrete.
Acesso aberto (Open Access)
Análise experimental do desempenho à flexão de vigas de concreto armado reforçadas com laminado de fibra de carbono com variação da taxa de armadura existente e do mecanismo de ancoragem
(Universidade Federal do Pará, 2025-06-17) LEÃO JÚNIOR, Paulo Sérgio Barreiros de; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
The strengthening of existing reinforced concrete structures with Fiber-Reinforced Polymers (FRP), using techniques such as Externally Bonded Reinforcement and Near-Surface Mounted, is common in practical applications, especially when using Carbon FRP (CFRP). However, in strengthening scenarios that require higher load capacities, these methods may be less effective due to premature debonding failure, highlighting the importance of anchorage systems to improve reinforcement efficiency. There is limited information in the literature regarding the influence of steel reinforcement ratio on the behavior of beams strengthened with anchorage systems. Therefore, this study experimentally investigates the flexural performance of reinforced concrete T-beams strengthened with CFRP, considering two steel ratios (0.44% and 1.12%) and two anchorage systems. Flexural tests were conducted on six T-section beams (2200 mm length, 280 mm height, 180 mm web width, and 80 mm thick by 350 mm wide flange). Each beam had 21 stirrups made of 12.5 mm bars spaced at 100 mm. For each steel ratio, one beam was unstrengthened (reference), and two were strengthened using either a friction-based mechanical anchorage (Hybrid Bonded – HB) or an anchorage system using bonded CFRP strips (FT). Strengthening was more effective in beams with the lower steel ratio, with strength increases of 58% for HB and 11% for FT. For the higher steel ratio, gains were limited to 10% for HB and none for FT. The HB system achieved a flexural capacity of 117.72 kN·m and showed better performance in intermediate displacements, with ductility increases up to 57 times at cracking and up to 100% at steel yielding. At maximum load, all strengthened beams showed reduced ductility. In the HB system, ductility loss increased with steel ratio, from 25% in the less reinforced beam to 49% in the more reinforced one. In the FT system, the trend was reversed, with a 66% loss for the lower steel ratio and 24% for the higher. Failure modes were governed by laminate slip in HB and cover delamination in FT.
Acesso aberto (Open Access)
Análise experimental do desempenho de conectores de cisalhamento de vergalhões dobrados para estruturas mistas via ensaios push-out
(Universidade Federal do Pará, 2022-11-25) SOUSA, Vanessa Carolaine de; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
Advances in civil engineering have led to the development of new techniques and materials that optimize the construction process. In this context, steel-concrete composite structures have emerged, which use steel and concrete efficiently through the collaborative work of the materials, exposing the metal part to tensile stresses and the concrete to compressive stresses. Shear connectors are essential in steel-concrete composite structures. They ensure the interaction between the materials and the transfer of stresses, making the structures lighter, stronger, and more durable. It is important to understand their operation and to seek new materials and technologies to optimize the structures. In this sense, this research continues the work of Souza (2019) and Barbosa (2016), who studied shear connectors made with CA-50 steel bars bent. The experimental program includes 7 models (varying the bar size, reinforcement rate, and the inclination of the connectors relative to the table of the metal profile) that were tested according to the recommendations of Eurocode 4 (2004). Of these 7 models, 2 were made with 12.5 mm rebar (models A1 and A2), 2 with 10.0 mm (models B1 and B2), 2 with 8.0 mm (models C1 and C2), and 1 model made with 6.3 mm diameter assembled in a single module (model D). When analyzing the load-carrying capacity/steel area ratio of the connectors, the results show that connector A1 (12.5 mm) had the best performance among the models in the study and also stands out when compared to other connectors studied such as those of Barbosa (2016), Souza (2019), and Chaves (2009). No significant evidence was observed that the inclination of the connectors positively affects the load-carrying capacity of the models. Analyzing the relative displacement between the profile and the slabs, it was possible to classify the models by ductility, in increasing order: D, A1, C1, C2, A2, B2, and B1. The 10.0 mm models have the highest ductilities, and the influence of the inclination of the connectors on this aspect is not clear. Analyzing the behavior in relation to uplift, it is noted that the best performances are in connectors B and C (10.0 mm and 8.0 mm) and there is a tendency for worse results in inclined connectors.
Acesso aberto (Open Access)
Análise experimental do desempenho de conectores de cisalhamento feitos em aço CA-50 para uso em estruturas mistas de perfis em aço e concreto armado
(Universidade Federal do Pará, 2019-10-25) SOUZA, João Pedro Nascimento de; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
The steel and concrete composite structures began to increase as a construction system over the years, due to their advantages both in their structural behavior and in their constructive aspects. These structures are those in which both materials (steel and concrete) work together, and for this to be possible, it is necessary to use connectors that combat the shear forces generated between the materials. There are several types of these connectors, but their goal is to make the structure solid and work monolithically. This work aims to experimentally analyze the performance of shear connectors, for use in steel and concrete reinforced composite structures, modifying geometries and arrangement of connectors composed of Ø 12.5 mm diameter CA50 steel bar bent in shape close to a truss, making a comparative to define which model offers the greatest contribution in the connection. Therefore, push-out tests were performed, following the procedure described in the European Standard Norm EN 1994-1-1 (2004), in 7 specimens, consisting of an 800 mm high welded I-metal profile, and two slabs of reinforced concrete, with dimensions of (600x600x150) mm, in contact with the top of flanges of the metallic profile, containing the welded connectors. Among the 7 models, 2 of them, named Isósceles Truss (IT) and Rectangular Truss (RT), were used as reference; in 4 of them were made variations on the arrangement of the connectors used on the reference specimens, which were named Slanted Isosceles Truss. (SIT), Slanted Rectangular Truss (SRT), Piramidal Isosceles Truss Type A (PIT A) and Piramidal Isosceles Truss Type B (PIT B), and in 1 was made a change on the geometry, which was named Straight Truss (ST). Regarding the load capacity, the ST connector presented a load gain of 10.82%, 32.94%, 19.53%, 34.51%, 30.98%, 23.14 % in relation to IT, RT, SIT, SRT, PIT A and PIT B, respectively. Taking into account the design resistance calculation (𝑃𝑅𝑑) of each connector according to EN 1994-11 (2004), the tested connectors had a load capacity 46.54% higher than 𝑃𝑅𝑑. The connectors, in their entirety, presented themselves as they are ductile in their breaking mode. Compared to the others, the RT connector presented a more rigid, and, the SRT, a more flexible behavior. Thus, it is observed that the proposed connectors presented a good performance in relation to the load capacity and rupture mode.
Acesso aberto (Open Access)
Análise experimental dos limites superiores de resistência à punção de lajes lisas de concreto armado com armaduras de cisalhamento
(Universidade Federal do Pará, 2018-10-30) FREITAS, Marcus Vinícius Pereira de; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479
In the flat slab system, the slab-column connection is a critical point due to the risk of punching shear failure. Several structural collapses are reported due to this mode of failure and constructive errors are the main causes of such accidents, leading researchers to study new shear reinforcement to minimize them. The use of shear reinforcement is the most efficient way to increase punching shear ductility and strength, but its correct arrangement generates conflict with the flexural reinforcement. Thus, Ferreira et al. (2016) propose a prefabricated truss reinforcement positioned internally to the flexural reinforcement, which generated the patent number BR 10 2015 006518 3 A2. Therefore, the work carried out in this research contributes to the investigation of cases of bidirectional shear for the present reinforcement. In this research, 5 experimental tests of reinforced concrete flat slabs submitted to symmetrical loading, containing both Stud Rails and the pre-fabricated truss reinforcement proposed by Ferreira et al. (2016) as shear reinforcement, were carried out. The study evaluated the performance of the reinforcement in relation to punching shear strength and analyzed the upper limits of strength, since a flexural reinforcement ratio of 2% and shear reinforcement ratios around 1% were used. The slabs were octagonal with a 2500 mm distance between parallel faces, side of 1036 mm and thickness of 210 mm, cast with concrete around 30 MPa and supported on columns with 400-mm-side. The following variables were analyzed: shear reinforcement type, slope and spacing of the shear reinforcement layers, as well as the design parameters of ACI 318 (2014), EC2 (2014), ABNT NBR 6118 (2014) and ETA 12/0454 (2012) codes. The experimental results show that the increase of load, in relation to the slab without shear reinforcement, reached up to 92%, with the use of pre-fabricated truss reinforcement, and 101% with the use of Studs, showing that the upper limit of ultimate load as a function of the concrete strength (Vu/Vc) can be limited to 2 and that the reinforcement studied in this research has a high commercial potential, since its cost per increment of load was lower than the one of the slab reinforced with Studs Rails, except for the design criteria suggested by ETA 12/0454, reducing the total cost by 15.6%.
Acesso aberto (Open Access)
Análise modal operacional: um estudo de caso da influência da alvenaria no comportamento dinâmico de prédios altos
(Universidade Federal do Pará, 2020-08-31) BORGES, João Pedro das Chagas; PRAZERES, Plínio Glauber Carvalho dos; http://lattes.cnpq.br/6175760351403329
Operational modal analysis consists on the modal parameters identification of a given structure from its normal operating conditions and is a reality in engineering applications, in line with the need for more precise and bold methods of structural monitoring. This dissertation aims to study and describe civil engineering structures operational modal analysis and, from its application, to study the masonry influence on the tall buildings dynamic behavior. In order to achieve the objective, two wellknown operational modal analysis methods were used as described in the text and it was showed that it is an important, viable and accurate tool for the Civil Engineering structures dynamic behavior identification. A sixteen-story building in the city of Belém-Pa was analyzed, before and after the masonry panels execution. Here consists the novelty in this work since it is very difficult to find building construction were the masonry is executed in the final construction stage only, what explain the lacking of studies with such characteristics. The study consisted on two measurement campaigns on four of the building's sixteen floors, with three points measure on each of these floors. The EFDD, in the frequency domain, and SSI, in the time domain, operational modal analysis methods were described and applied in the building modal identification in both campaigns. Satisfactory results were achieved and they were validated by the MAC coefficient. The identified natural frequencies had increases in a range from 25% to 35% in the masonry executed structure in relation to the reinforced concrete porch without masonry, which is structure's stiffness gain evidence. In addition, it was observed that this stiffness gain is considerably greater in one of the building's bending directions, indicated by a modal shapes inversion between the first two vibration modes when compared the two campaigns. Through these results, it was concluded that the masonry had significant interference in the building dynamic behavior.