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Navegando por Orientadores "MORAES NETO, Bernardo Nunes de"

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    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.
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    Eficácia da ABNT NBR 6118 (2014) na previsão da carga última de pilares curtos/esbeltos em concreto armado sujeito à flexão composta normal.
    (Universidade Federal do Pará, 2019-11-27) LEITE, Jonas dos Santos; MORAES NETO, Bernardo Nunes de; http://lattes.cnpq.br/5790058515094077
    Once the short/slender reinforced concrete columns theory has been slightly presented in the national technical/scientific literature, it could be considered as a research goal working up this kind of publication. However, bringing about the accuracy judgment of the ABNT NBR 6118 (2014) design guidelines to predict the load-carrying capacity for short/slender reinforced concrete columns under combined axial load and bending has been the outstanding inquiry target. Wherefore, both the simplest proposals as well as the accurate one have been introduced and taken stock herein. It is worth underscore that two concepts have marked the simplest proposals, namely, standard-column methods with approximate curvature (AC method) and approximate stiffness (AS method). Thus, the interaction diagram concepts together with load-moment curves (P-M), which were addressed in a linear (L) and nonlinear (NL, geometrical issue) way, had accounted for the accurate method. To vouch for the scrutiny undertook before, 17 experimental investigations, which had added up to 320 reinforced concrete columns, composed the database (DB) handled currently. From then on, the performance index ξ has been embraced and assessed by means of descriptive statistic thought, where ξ = Pexp/Ptheo (Pexp = experimental failure load recorded in the DB and Ptheo = theoretical/predicted failure load). Ended up the quest, the effectiveness of whole design guidelines to predict the failure load for short/slender reinforced concrete columns from DB was bearing out by the results had brought forth herein. Notwithstanding the previous positive outcome, it was also pointed out that predicting the failure load of slender columns with slenderness ratio high than 35 the P-M (L) proposal had been in an unsafe condition.
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    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
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    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.
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