Utilização de concreto reforçado com fibras no projeto de vigas submetidas à flexão

Abstract

The Fiber-Reinforced Concrete (FRC) is being widely used on structural reinforcement actions due to, among other advantages, granting ductility to a body that presents a brittle failure behavior by itself. This occurs because the fiber has a bridging effect on micro-cracks, diminishing the resultant stress concentration caused by fractures. Besides, the size reduction of micro-cracks also allows a higher resistance against the entrance of potential harmful external agents, increasing the structural durability. The FRC utilization also provides a mechanical performance increase against bending stresses, as officialized in 2021 by the Associação Brasileira de Normas Técnicas (ABNT). Therefore, this work presents aims the implementation of a sizing method adopted in Brazil for FRC beams subjected to bending stresses, employing it in distinct circumstances in order to thoroughly evaluate the influence of the model utilized, the concrete characteristics and the incorporated fiber ratio. Besides that, this work also assesses the economic viability of the fiber incorporation by comparing it against the budget used for standard concrete structures. Thus, considering the method presented by the ABNT NBR 16935:2021 - Projeto de estruturas de concreto reforçado com fibras – Procedimento, an Excel sheet was developed in order to evaluate the mechanical capacities and also to complete the sizing procedure for beams subjected to bending stresses for both proposed models in the previously cited NBR: Linear and rigid-plastic. Given the experimental results found within the literature, the structural analysis process was completed by the sheet employment. Thereupon, the results presented in this work numerically show the influence of multiple factors already defined on the sizing of Fiber-Reinforced Concrete beams subjected to bending stresses, as well as an evaluation on the expenses comparing structures of the aforementioned concrete against standard ones. This work concludes that the structural performance for beams subjected to tension by bending stresses increases along with the incorporated fiber ratio, which implies a smaller steel reinforcement area in these bodies. Besides, it is more efficient in low-resistance classes of concrete. It is important to highlight that the linear model presented a more conservative performance when compared to the rigid-plastic one. Also, about the implementation cost, it is indeed bigger for FRC beams subjected to the aforementioned stresses, but it presents a better competitiveness when qualitative variables are taken into consideration.