Numerical assessment of concrete flexural members reinforced by FRP rebars.

• Ano de defesa: 2020
• Autor(a) principal: Barbosa, Felipe Augusto da Silva
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Armadura não metálica; Concreto armado; Concreto protendido; Efeitos diferidos no tempo; Fiber-reinforced polymer; FRP; Long-term effects design program; Non-metallic reinforcement; Polímeros reforçados por fibras; Prestressed concrete; PRF; Programa de dimensionamento; Reinforced concrete
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/3/3144/tde-14012021-123256/

The FRP - Fiber-Reinforced Polymer - reinforcement consists of an alternative material to replace the conventional steel in reinforced concrete structures. Besides being corrosion resistant, FRP is lightweight and has high tensile strength, being successively utilized in sea walls, magnetic resonance units, garage parks and bridges. However, the FRP stress-strain relationship is linear up to failure, not exhibiting a yielding plateau. It also has low elasticity modulus and presents sudden failure if subjected to high sustained stresses. Thus, this research evaluated the steps for the design of flexural members reinforced and prestressed with FRP rebars and strands, respectively. Their structural behavior was also numerically investigated and compared to that regarding the same members reinforced and prestressed with steel. Furthermore, the long-term behavior of one beam reinforced with different ratios of Glass FRP was evaluated from the short-term response to a period of one hundred years. The parameters for the long-term numerical assessment were based on design codes and experimental test results. Additionally, three axially loaded prismatic members and three simply supported beams were modeled to investigate the use of FRP in prestressing. The purpose was to obtain the axial force-strain and moment-curvature relationships, as well as to evaluate the cracking behavior and compare the performance of FRP prestressed members to those with steel. Finally, the equations for the design of rectangular and T/L cross-section shapes were developed through equilibrium and compatibility, considering the Navier\'s hypothesis. Those formulations were implemented to a code, which resulted in a design program that calculates the required FRP area for different concrete compressive strengths. For the cases in study, the results indicated that the creep rupture limit state usually governs the design of cross-sections reinforced with Aramid and Glass FRP, leading to over-reinforced cross-sections. In contrast, using Arami and Carbon FRP in prestressing proved to be effective in comparison to the conventional steel. They exhibited higher flexural strengths and less intense cracking, with no need to overreinforce the cross-sections. Regarding the long-term behavior, changes in the concrete constitutive properties resulted in increases in the flexural strengths and changes in the failure mode. Moreover, deflections and crack widths exhibited the highest rate of increase during the first five years, stabilizing around the age of seventy years.