Navegando por Assunto "Ancoragem"

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Acesso aberto (Open Access)
Aderência de armadura em concreto reforçado com fibra de aço
(Universidade Federal do Pará, 2018-02-22) ROSSI, Carlos Rodrigo Costa; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
This work evaluates the influence of steel fibers on the bond between reinforcement and concrete and the behavior of beams subjected to bending stress in the Ultimate Limit State, through an innovative test to compare with RILEM RC6 (1983) standard test. Some of the theoretical models that are willing to represent the bond behavior are prescribed by CEB-FIP (2010), ACI 408R (2003) and NBR 6118 (2014) and by the authors' proposed models: Orangun et al. (1977), Harajli (2009), Shen et al. (2016). In the experimental program will be analyzed steel bars with diameters of 8 mm, 10 mm and 12.5 mm in specimens molded with compressive strength concrete of 30 MPa, varying the length of development in lb; 0.75.lb and 0.5 lb (lb is anchorage length determined by NBR 6118, 2014). The steel fibers used with volumes ranging of 0; 39.25; 78.50 and 117.75kg/m³. There will be 27 beams for the proposed test and 12 cube for the standard Pull-Out Test. The beams were tested at 28 days after concreting, the experimental results were presented and compared with the normative predictions. In the standard test for Vf = 0.5%, increase of tension ≈ 4%, for Vf = 1.0%, increase of tension ≈ 11% and Vf = 1, 5%, increase of tension ≈ 15%. In the proposed test, since there was also variation of length development, the best results were for samples with Vf of 1.5% and with 0.5.lb presented higher tension and load of equivalent rupture. In relation to the theoretical analysis, it was concluded that the prescriptions of Orangun et al. (1977) and ACI 408R (2003) presented results closer to the experimental results, exp/teo ≈ 1, and presented a security level of 75% in the evaluation of security level and dispersion. Therefore, it is feasible to state that lengths developments of smaller CRFA exhibit behavior and performance similar to the lengths developments of reinforced concrete and that the work proposed is efficient for the study of the influence of steel fibers in the bond between reinforcement and concrete.
Acesso aberto (Open Access)
Influência do detalhamento dos estribos na resistência à punção de lajes lisas de concreto armado
(Universidade Federal do Pará, 2021-09-15) COSTA, Mayara Gonçalves; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479
Stirrups used as punching shear reinforcement in reinforced concrete flat slabs can provide strength gains to the regions of slab-column connection. To this end, the standards recommend that the details should be made in order to ensure their anchorage in the flexural reinforcement bars, involving them. However, designs that strictly follow the detailing criteria may become difficult to execute, or even unfeasible, due to the concentration of longitudinal bars in these regions. The need for more practicality in the assembly of stirrups has driven the development of reinforcement systems, whose anchorage details are not yet contemplated in the normative prescriptions. Therefore, the scientific validation of such constructive alternatives is necessary. In this context, this work seeks to contribute to the validation process of numerous constructive alternatives for stirrups used as punching shear reinforcement, so that, in this way, they can be properly disseminated in the technical environment. The objective of this work is to evaluate the influence of the variation of the stirrups anchorage on its efficiency, from an extensive review of scientific literature, which enabled the assembly of a database containing 119 punching shear tests in internal slab-column connections, subjected to symmetric loading. The analysis parameters were the increments of strength provided as a function of the increase of force played by the shear reinforcement. At the end, the most efficient anchorage details for different types of stirrups used as punching shear reinforcement were defined and, for such stirrups, assembly instructions were proposed, aiming the optimization of the constructive process.