Publicação
Innovative methodologies for the enhancement of the flexural strengthening performance of NSM CFRP technique for RC beams
| Resumo: | Carbon fiber reinforced polymer (CFRP) materials have been extensively adopted for the flexural and shear strengthening of RC structures due to their several advantages, like a low mass density, a high strength and stiffness to weight ratios, excellent fatigue behavior, non-susceptible to corrosion, and high durability in typical environment conditions of civil engineering constructions. These CFRP composite materials can be applied to RC structures to be strengthened by using either externally bonded reinforcing (EBR) or near surface mounted (NSM) techniques. The main purpose of the current study is to experimentally evaluate the efficiency of two flexural strengthening methodologies using the NSM CFRP technique for the enhancement not only the load carrying capacity at concrete cracking and steel yielding initiations, serviceability limit state, and ultimate condition, but also the ultimate deflection capacity when compared to the use of non-prestressed NSM CFRP technique. The investigated strengthening methodologies include NSM prestressing and NSM hybrid techniques. In the NSM prestressing technique, an appropriate prestress level is applied on the CFRP reinforcement, while the NSM hybrid technique combines nonprestressed and prestressed CFRP reinforcements in the same application. Moreover, the distribution of tensile strain and bond shear stress along the prestressed NSM CFRP reinforcement is experimentally evaluated after the release of prestress force. On the other hand, the experimental tests are simulated using a nonlinear finite element (FE) model, which considers the nonlinear behavior of the constituent materials, the behavior of CFRP-epoxy adhesive-concrete interfaces, and modeling the prestress process of the CFRP elements adopted in the experimental tests. Besides, simplified analytical approaches, with a design framework, are developed to predict the flexural behavior of RC beams flexurally strengthened with prestressed CFRP reinforcement applied according to either EBR or NSM techniques. Moreover, this study offers an analytical formulation based on a closed form solution for the prediction of the distribution of CFRP tensile strain and bond shear stress and, additionally, the prestress transfer length immediately after the release of the prestress force. |
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| Autores principais: | Rezazadeh, Mohammadali |
| Assunto: | NSM technique Composite materials Prestressing Hybrid system Numerical analysis Analytical approach Prestress transmission zone Técnica NSM Materiais compósitos Pré-esforço Sistema híbrido Análise numérica Formulações analíticas Zona de transmissão do pré-esforço Engenharia e Tecnologia::Engenharia Civil |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Carbon fiber reinforced polymer (CFRP) materials have been extensively adopted for the flexural and shear strengthening of RC structures due to their several advantages, like a low mass density, a high strength and stiffness to weight ratios, excellent fatigue behavior, non-susceptible to corrosion, and high durability in typical environment conditions of civil engineering constructions. These CFRP composite materials can be applied to RC structures to be strengthened by using either externally bonded reinforcing (EBR) or near surface mounted (NSM) techniques. The main purpose of the current study is to experimentally evaluate the efficiency of two flexural strengthening methodologies using the NSM CFRP technique for the enhancement not only the load carrying capacity at concrete cracking and steel yielding initiations, serviceability limit state, and ultimate condition, but also the ultimate deflection capacity when compared to the use of non-prestressed NSM CFRP technique. The investigated strengthening methodologies include NSM prestressing and NSM hybrid techniques. In the NSM prestressing technique, an appropriate prestress level is applied on the CFRP reinforcement, while the NSM hybrid technique combines nonprestressed and prestressed CFRP reinforcements in the same application. Moreover, the distribution of tensile strain and bond shear stress along the prestressed NSM CFRP reinforcement is experimentally evaluated after the release of prestress force. On the other hand, the experimental tests are simulated using a nonlinear finite element (FE) model, which considers the nonlinear behavior of the constituent materials, the behavior of CFRP-epoxy adhesive-concrete interfaces, and modeling the prestress process of the CFRP elements adopted in the experimental tests. Besides, simplified analytical approaches, with a design framework, are developed to predict the flexural behavior of RC beams flexurally strengthened with prestressed CFRP reinforcement applied according to either EBR or NSM techniques. Moreover, this study offers an analytical formulation based on a closed form solution for the prediction of the distribution of CFRP tensile strain and bond shear stress and, additionally, the prestress transfer length immediately after the release of the prestress force. |
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