Navegando por Assunto "Steel fibers"

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Acesso aberto (Open Access)
Análise do comportamento mecânico de tubos de concreto com fibras de aço produzidos com materiais da região metropolitana de Belém do Pará
(Universidade Federal do Pará, 2015-09-25) OLIVEIRA, Marco Antonio Barbosa de; POMPEU NETO, Bernardo Borges; http://lattes.cnpq.br/6564259204591721; MACEDO, Alcebíades Negrão; http://lattes.cnpq.br/8313864897400179
The steel fibers in the concrete pipes have provided better mechanical performance levels. In the northern region, uniquely in Belem, no studies on the technical feasibility of this technological resource, although there is considerable deficiency of urban infrastructure. Thus become relevant conduct studies on alternative technology. This study seeks to analyze the mechanical behavior of concrete pipes with steel fibers, aiming at the technical feasibility of replacing the concrete pipe with conventional armor. The research methodology we used steel fibers in loose state and glued comb DRAMIX® 3D type 65/35 and 80/60 DRAMIX® 3D type. For each fiber type were adopted contents of 20 kg / m³ (0.25%), 30 kg / m³ (0.38%) and 40 kg / m³ (0.50%) by weight and volume fraction, respectively. The size of all concrete pipes was 600 mm diameter, wall thickness of 60 mm and effective length 1000 mm, and the cylindrical bodies of the test piece of 100x200mm and prismatic of 150x150x500mm and 150x150x550mm, which were subjected to the tests for mechanical behavior evaluation and durability. In the production of concrete with the fibers was reviewed in the fresh state with frustoconical rebate between 0 and 10 mm. The dosage of concrete with fibers was routinely employed by the company for concrete without fibers, and the strength of the fibers takes place under the rule of the mixture. The results obtained that the concrete pipe with fiber type 80/60 loose at all levels and pasted comb the levels of 0.38% and 0.50%, reached the minimum breaking load and post-cracking set by the NBR 8900 (ABNT, 2007), thus would be technically feasible as the replacement of reinforced concrete pipes conventionally, under the conditions and specifications of this study.
Acesso aberto (Open Access)
Análise experimental da eficiência das fibras de aço no reforço ao cisalhamento de vigas em concreto armado
(Universidade Federal do Pará, 2016-08-29) GOMES, Lana Daniele dos Santos; MORAES NETO, Bernardo Nunes de; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
The present study aims to assess the efficiency of steel fibres for shear strength of reinforced concrete beams. For this purpose, some design guidelines were discussed together with an experimental research. For the guidelines analysis, five proposals are presented, RILEM TC 162-TDF (2003), CECS 38 (2004), JSCE (2008), EHE 08 (2010) and MODEL CODE (2010). Within this analysis, the proposals performance were assess from the Vexp/Vteo parameter, which corresponds, respectively, the experimental results, which will be collected from the scientific literature, composing a database (DB), and the theoretical results, which are estimated according to the design guidelines. For the experimental research, four beams are evaluated, where one beam is the reference one (no fibres), and the others are built with steel fibres reinforced concrete (SFRC). It is important to note that all beams are reinforced for shear strength by a minimum amount of web reinforcement (stirrups). For the SFRC beams, two conditions will be discussed. Firstly, the influence of the fiber content (Cf) added to the concrete, which range in 0,5% (≈40 kg/m3), 0,8% (≈60 kg/m3) and 1,0% (≈80 kg/m3) and finally, the possibility to replace conventional web reinforcement (stirrups) by steel fibres reinforcement. The theoretical analysis, it was concluded that the guidelines MODEL CODE (2010), CECS 38 (2004) and JSCE (2008), have provided the best results agreed with Vexp / Vteo≈1,0, however, JSCE (2008) was the most penalized according to the modified version of the DPC (Demerit Points Classification), proposed originally by Collins (2001). RILEM TC 162-TDF (2003) behaved conservatively and EHE 08 (2010) showed more dispersed results. In relation to experimental research, although it was recorded a resistance increases of 20% for concrete with Cf = 1.0%, the axial compression tests, however, the most significant gain was recorded as ductility and toughness the SFRC, to the point of changing the way of breaking the beams, shear (reference beam) for bending (beams with SFRC).
Acesso aberto (Open Access)
Aplicando concreto de elevada resistência reforçado com fibras de aço na supressão do reforço convencional de vigas em concreto armado de resistência normal
(Universidade Federal do Pará, 2020-01-14) SOUSA, Elielson Oliveira de; MORAES NETO, Bernardo Nunes de; http://lattes.cnpq.br/5790058515094077
High strength steel fiber reinforced concrete (HS-SFRC) used as suppression of conventional reinforcement normal strength reinforced concrete beams (NS-RC) has been in the current experimental research. Five 150x300x2700 mm³ size beams were prepared and submitted to four point bending test until failure. The beam reference have been produced without steel fibers (fc = 30.0 MPa), with longitudinal reinforcement ratio (ρl,t = 0.91%), and transverse reinforcement (ρw = 0.11%), representative of practice applications. Four other HS-SFRC beams were produced with fc = 60.0 MPa, ρl,t = 0.39% (≈ 60.0% suppression relative to reference beam), ρw = 0.0 % (100.0% suppression) and fiber consume (Cf) alternating in 45,0,60,0, 75,0 and 90,0 kg/m³. The behavior beams was analyzed from load-displacement and moment-curvature relations. The viability to design HS-SFRC beams with suppression conventional reinforcements was verified based on these results and material characterization tests, exposing equivalent mechanical behavior and some cases higher that of NS-RC beams.
Acesso aberto (Open Access)
Eficácia das fibras de aço no reforço ao cisalhamento de vigas de concreto armado sem estribos: investigação experimental
(Universidade Federal do Pará, 2019-11-27) MAUÉS, Kássio Anderson Castro; MORAES NETO, Bernardo Nunes de; http://lattes.cnpq.br/5790058515094077
Several research papers have been dedicated to the investigation of the behaviour of steel fibre reinforced concrete (SFRC) under several types of forces. Due to its mechanical property to transfer forces through cracks, it has been observed that SFRC presents substantial contribution to shear resistence. The present paper investigates the effects of steel fibres on the shear reinforcement of concrete beams without stirrups under four-point bending tests. For that purpose, five beams were cast and tested. The dimensions of the beams were 150 mm×300 mm×2700 mm, with 1.54% and 0.16% of tension and compression longitudinal reinforcement ratios, respectively. Two of the beams were manufactured as references, that is, without fibres, with one of them having conventional transversal reinforcement with stirrups and the other with no reinforcement to shear. The other three beams were reinforced with steel fibres only in the shear span in the proportions of 45 kg/m³, 60 kg/m³ and 75 kg/m³ of the concrete volume, which represent 0.6%, 0.8% and 1.0%, respectively. Concrete strength of 30 MPa was used for all the specimens. In addition to the typical characterization of concrete and steel used in this research, flexural test was performed on SFRC in order to obtain the residual stress response of the material, whic h is paramount for the evaluation of the strength of the beam. From the experimental results, it could be concluded that steel fibres exhibited satisfatory performance under shear forces in the cases of higher fibre content, for which a change in failure mode was observed: from shear failure to flexural failure. Furthermore, for the three fibre contents used, the possibility for partial or total replacement of the transversal reinforcement was confirmed. Additionally, it was demonstrated that the use of steel fibres in the content of 60 kg/m³ and 75 kg/m³ allows for the reduction of the longitudinal tension reinforcement to attain flexural strength similar to that of the reference beam with stirrups
Acesso aberto (Open Access)
Experimental analysis of the efficiency of steel fibers on shear strength of beams
(Associação Brasileira de Ciências Mecânicas, 2016-07) GOMES, Lana Daniele dos Santos; OLIVEIRA, Dênio Ramam Carvalho de; MORAES NETO, Bernardo Nunes de; MEDEIROS, Adelson Bezerra de; MACÊDO, Alcebíades Negrão
The efficiency of steel fibers for shear strength of reinforced concrete beams is assessed. Four beams were evaluated: control consisted of one beam without any steel fibers and three beams with reinforced concrete with steel fibers. All beams were reinforced for shear strength by a minimum reinforcement rate. The influence of fiber content added to concrete, at 0.5%, 0.8% and 1.0%, and the possibility of partial or total replacement of conventional shear reinforcement (stirrups) by steel fibers were evaluated. Results showed a significant increase in ductility and stiffness of the beams with steel fibers and, consequently, changes in the failure mode were observed, of shear (control beam) to flexure behavior (beams with steel fibers).
Acesso aberto (Open Access)
Impacto da inércia de seções retangulares e do consumo de fibras na resposta estrutural de vigas contínuas em CRFA solicitadas por carga distribuída: campanha experimental
(Universidade Federal do Pará, 2023-01-25) MONTEIRO, Paulo André dos Santos; MORAES NETO, Bernardo Nunes de; http://lattes.cnpq.br/5790058515094077
In order to play up the proper selection of rectangular section inertia on flexural design of steel fibre reinforced concrete beams, SFRC beams, an experimental campaign has been introduced. Presently, four beams have been tested, where the reference one, with cross section of 150x300 mm2, was in reinforced concrete, RC, and three beams were in SFRC. The rectangular section inertia judgment was on SFRC beams only, where their cross-sections varied in 150x300, 110x400 and 90x500 mm2. The cross-section areas of those beams were constants and their fibre contents were 75, 60 and 45 kg/m3 on concrete volume, respectively. Under those circumstances, the conventional reinforcement arrangements, i.e., steel rebar details, were alternated as well as suppressions were also executed on SFRC beams. Nevertheless, all SFRC beams have carried the reference strength, which meant, the RC beam strength. In addition, it is worth mentioning that all questions called before were carried on continuous beams, where normal and transverse stresses are concomitantly relevant, under uniformly distributed loading. As a conclusion, the results have shown the effectiveness of steel fibres, as a reinforcement alternative, and the advantages of a proper inertia in design issues, warranting the reference strength, even using less reinforcement, both rebars and fibres. Now, concerning to design guidelines, MC10 (2013) proposals have been handled. Herein, applying those letters of support, an interactive methodology was introduced to figure out the flexural strength of RC and SFRC beams, taking, at the same time, all description of reinforcement influence, longitudinal/transverse rebars and fibres. To conclude, in order to improve, in the future, the design of continuous beams uniformly distributed loading, some advices have also been announced.
Acesso aberto (Open Access)
Proposta analítica para estimar as resistências residuais à tração por flexão em concreto reforçado com fibra de aço
(Universidade Federal do Pará, 2022-06-15) CASTRO, Lana Daniele dos Santos Gomes; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
This research presents equations that estimate the residual resistances, fRi (i = 1 to 4), based on the main parameters that influence the performance of steel fiber reinforced concrete (SFRC), such as the geometric properties of steel fibers, the concrete compressive strength (fc) and fiber volume fraction (Vf). For this purpose, the research was divided into three stages, the first one consisted of creating an extensive and diversified database to, from it, develop the residual resistances equations through multiple regression. The next stage was experimental, composed of 15 beams (150x150x550) mm notched and tested to flexural tension, with variable fiber volumes, with contents of 0.0%, 0.5%, 1.0%, 1.5% and 2.0%. Finally, for the analysis of the equations elaborated in the first step, another database is presented, in which experimental results collected from the literature and those obtained in this research were inserted, and, additionally,performance comparisons were performed with four other existing analytical models. It was concluded that the analytical proposal presented by this study to define the residual resistances, in comparison with the other existing empirical models, stood out for its good performance, since it was the most accurate, less penalized and dispersed, demonstrating the reliability of the equations.