Browsing by Author "Alfaiate, J."
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- Análise do comportamento de vigas de betão armado reforçadas à flexão simples com CFRPPublication . Neto, Pedro; Alfaiate, J.; Vinagre, JoãoO reforço de estruturas de betão armado com recurso a CFRP é actualmente uma prática corrente. Este artigo tem como objectivo ilustrar a aplicação de um modelo numérico ao caso de uma viga simplesmente apoiada com quatro pontos de carga. Pretende-se aferir da importância dos modos de rotura locais provenientes de tensões de corte ao nível da interface, no comportamento à rotura de um elemento à flexão simples.
- The influence of the mode II fracture energy on the behaviour of composite plate reinforced concretePublication . Neto, Pedro; Alfaiate, J.; Almeida, J. R.; Pires, E. B.; Vinagre, JoãoIn this paper, the finite element method is used to analyse the behaviour of concrete externally strengthened by sheets of carbon fibre reinforced polymer (CFRP). The bond between concrete and CFRP is modelled by a discrete approach using interface elements. The mechanisms involved in the behaviour of externally reinforced concrete specimens are complex, the global strength of the specimen being governed by the strength of each individual material as well as by the adhesion properties conferred by the epoxy. It is observed in experiments that, in most cases, failure occurs due to the loss of cohesion of a portion or lamina of concrete attached to the epoxy-fibres layers, the latter remaining intact. In this paper, the results of numerical simulations of bond tests are presented, aiming to contribute for a better understanding, in qualitative and quantitative terms, of mode II fracture energy in concrete and its influence on the behaviour of the interface concrete-FRP.
- Modelação da aderência entre o betão e materiais de reforçoPublication . Neto, Pedro; Vinagre, João; Alfaiate, J.O sucesso do reforço de estruturas de betão armado, com recurso à técnica de colagem de materiais compósitos, está intimamente relacionado com o comportamento da ligação entre o betão e o FRP. A correcta quantificação da aderência entre estes materiais é pois, um aspecto que tem vindo a merecer atenção crescente, apresentando-se resumidamente neste artigo, os principais modelos matemáticos para a modelação da ligação por aderência.
- Modelling the behaviour of reinforced concrete beams strengthened with FRPPublication . Neto, Pedro; Alfaiate, J.; Vinagre, JoãoThe strengthening of reinforced concrete structures with fiber reinforced polymers (FRP) is particularly attractive due to their mechanical properties. The understanding of the premature failure modes is of great importance. Since rupture is frequently found to occur at the interface FRP concrete, there is a clear need to study the nature of the bonding so as to develop techniques to permit its design modeling. The stress distribution in shear test models does not precisely match the one obtained in flexural reinforcement; in the latter, according to various authors [1, 2], in addition to the stresses tangential to the interface, normal stresses are also important. In this paper, a numerical model is presented to describe the behavior of reinforced concrete beams strengthened with FRP. This model is based on previous studies focused both on: i) the distribution of shear stresses at the interface FRP concrete and on ii) the stress concentration at the plate ends in flexural models. Furthermore, the importance of the flexural cracks in the premature rupture of the element is also analyzed. The behavior of reinforced c concrete beams strengthened with both FRP laminates and sheets is considered. The FRP epoxy concrete arrangement and the flexural cracks are modeled with interface elements with initial zero thickness, using a discrete approach and a localized damage model. A softening behavior is adopted to simulate the stress transfer along the FRP- -concrete interface. The importance of considering the mixed mode of fracture is discussed. Mention is also made to some of the main mathematical models found in the literature.