Programa de Pós-Graduação em Engenharia de Infraestrutura e Desenvolvimento Energético - PPGINDE/NDAE/Tucuruí
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Item 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/0000-0002-5911-1368Reinforced 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.Item 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/0000-0002-5911-1368For 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.Item 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/0000-0001-8905-9479The 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.Item 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/0000-0002-5911-1368Short 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.Item 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/8912916360456192Short 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.Item 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/0000-0002-5911-1368The 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.Item 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/0000-0002-5911-1368The 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.Item Acesso aberto (Open Access) Cisalhamento em vigas de concreto armado com armadura transversal interna contínua(Universidade Federal do Pará, 2019-09-24) SOUZA, Diego Ferreira de; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368Reinforced concrete elements can suffer high bending and shear forces, either due to high loads, type of construction or architectural limitation, thus requiring a high longitudinal and transverse reinforcement rate, which can lead to conflicts between the two reinforcements, resulting in reduced productivity during the reinforcement work of the element. As a way to solve this reinforcement conflict, some researchers applied to reinforced concrete elements internal shear reinforcement, in other words, these reinforcements are positioned between the bending reinforcement bars, thus eliminating the conflict between the transverse and longitudinal bars and aiding the productivity of the reinforcement work, as this type of elements could be prefabricated and positioned as designed. However there are no normative standards that indicate the use of internal stirrups. Studies conducted on the subject indicated that the internal stirrups need an auxiliary device, as recommended by NBR 6118 (2014), which would help in the anchorage and allow the transfer of shear forces to the concrete without the delamination effect. Currently, few studies evaluate the performance of the transverse reinforcement with inclinations between 45º and 90º, where inclined stirrups provide better ductility and reduced stresses on compression struts. Therefore, this research presents a type of internal transverse reinforcement, tested in an experimental program and compared with closed-loop stirrups. The experimental program was carried out with a total of 5 beams of reinforced concrete, one as a reference with closed-loop stirrups, and the other 4 with internal stirrups; the main variables were: the inclination of the internal transverse reinforcement at 60º and 90º; and the number of legs of internal transverse reinforcement, keeping the same transverse reinforcement ratio. As results, this paper presents graphs of displacements, bending and shear reinforcement and concrete deformations, cracking maps and failure surfaces, and the last loads observed in the tests were compared with the theoretical loads estimated by different normative recommendations. As conclusions, it was observed that the internal stirrups have great potential in their use, as they present greater ductility and resistance compared to the closed-loop stirrup currently used. The results of inclined internal stirrups showed an increase of up to 14% when compared to the reference beam.Item Acesso aberto (Open Access) Efeito da taxa de armadura existente e do sistema de ancoragem na resistência à flexão de consolos curtos de concreto armado reforçados com laminados de PRFC(Universidade Federal do Pará, 2025-06-13) LIMA, Layse Rafaele Furtado; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479Short corbels are elements used in bridges and buildings to support beams, stringers or concentrated loads of great intensity, and are characterized by having a span-to-height ratio of less than one. Over the course of their useful life, these structures can fail to meet basic safety requirements for reasons such as design error, material degradation, overload or change in use, requiring reinforcement techniques that can be applied quickly and efficiently. With this in mind, this work seeks to experimentally analyze short reinforced concrete beams reinforced externally in bending with Carbon Fiber Reinforced Polymer (CFRP) laminates. To this end, six specimens were analyzed, three with a 0.18% flexural reinforcement rate and three with a 0.47% rate. All the models have the same geometry, with the presence of horizontal and vertical stirrups. The reinforcement was positioned on both sides of the cantilever and anchored at the ends, checking the influence of two systems. The first anchoring system is made up of steel plates and bolts, while the second is made up of overlapping laminates, with transverse bonding in the last layer. As a result, it was possible to analyze that the reinforcement proved to be efficient in terms of increased resistance, which ranged from 14,5% to 50,3%, with the hybrid anchorage standing out as having the highest loading value.Item Acesso aberto (Open Access) Influência da substituição de agregados naturais por reciclados de concreto na resistência à punção de lajes lisas de concreto armado com armadura de cisalhamento(Universidade Federal do Pará, 2023-11-21) PORTILHO, Shara Katharine Melo Silva; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368This research experimentally analyzed the mechanical behavior of four reinforced concrete flat slabs with shear reinforcement, when subjected to punching shear forces. Two of these slabs were made using a concrete mixture with a total replacement of natural coarse aggregates (NGA) by recycled concrete coarse aggregates (RCCA), and two slabs served as reference (without replacement). Shear reinforcement had two types: double headed studs and individual stirrups. The specimens were octagonal in shape, with 2,500 mm between opposite faces, thickness of 210 mm, and were supported on square central columns measuring 300 mm on each side. The estimated average concrete strength was 25 MPa, and the flexural and punching shear were 1.4% and 0.34%, respectively. After the laboratory tests, a comparison was made between the experimental behavior and the theoretical predictions from ABNT NBR 6118 (2023), Eurocode 2 (2014), ACI 318 (2019), and the fib Model Code 2010 (2013) models. Regarding the use of shear reinforcement, the results showed that the slabs with double headed studs presented higher punching shear strength when compared to those with individual stirrups. It was also observed that slabs with a total replacement of natural coarse aggregates by recycled concrete aggregates presented lower punching shear strength than slabs with natural aggregates. Regarding the comparison between the estimated punching shear strength of the flat slabs with shear reinforcement using RCCA prescribed by the analyzed codes and the experimental results, it was found that almost all code predictions were very close to the experimental values, except for the Brazilian code, which indicated results against safety.Item Acesso aberto (Open Access) Influência do espaçamento das armaduras de cisalhamento na resistência à punção de lajes lisas com estribos treliçados pré-fabricados(Universidade Federal do Pará, 2022-12-27) COSTA, Denilda Silva; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479The shear check on the slab-column connection of flat slabs in reinforced concrete is the critical point of design in the ultimate limit state. Punching failure is the critical point in the design of flat slabs and is defined as a sudden and fragile failure due to shears in the region of connection between the slab and the column, the best option for the control of failure by flat slabs is to use of shear reinforcement. National and international regulations such as the use of shear reinforcements that involve bending reinforcements in a way that their anchoring is guaranteed. However, this model makes the executive process difficult, requiring configurations between the bending and shear protections at the construction site. This research aims to present a technical and constructive solution to the problem of shear resistance in flat slabs in the slab-column connection through the use of shear reinforcement proposed by Ferreira et al. (2016), prefabricated truss stirrups, varying the values of the shear reinforcement rates and the spacing between the reinforcement layers. Positioned between the upper and lower flexural reinforcements, it has speed in execution and the possibility of manpower, as it is industrially bent and positioned on the job site, the useful height of the slab and the economy eliminates conflicts between the shear and flexural reinforcements. To compare the results and analyze the performance, tests were carried out on 5 flat reinforced concrete slabs, one of the slabs was reinforced with a flexural reinforcement rate ρ 2,0%, and the others with ρ1%, the reinforcement rate of shear (ρw) varies from 0.49% to 0.99%. As the instrumented in a way that could be the non-designed displacement forms, as in the flexural, shear and complementary reinforcements. The slabs were instrumented so that the vertical displacements, the deformations in the concrete and in the flexural, shear and complementary reinforcements could be obtained. The slabs were dimensioned so that the failure occurred by punching within the region of the shear reinforcement following the normative calculation recommendations of NBR 6118 (ABNT, 2014), ACI 318 (2019), Eurocode2 (2014), fib Model Code 2010 (2013) and the EOTA technical report (2017). From the analysis of the results, it was concluded that all slabs failed by punching, the slabs reinforced with prefabricated truss stirrups showed a strength gain of 73% for the SW3 slab when compared to the reference slab (S0) from Freitas (2018) and of 55%, 58%, 45% and 50% for slabs SW4, SW5, SW6 and SW7, respectively, when compared with the predictions of NBR 6118 (ABNT, 2014), slabs with reinforcement positioned up to 1.125d from the column face showed higher strength increase values and ultimate strength values similar to those of slabs with constant spacing, even with reduction of the total amount of steel by up to 95,2% of its weight.