Prediction of Load Capacity Variation in FRP Bonded Concrete Specimens Using Brownian Motion

Abstract

In wet lay-up process, dry fiber sheets are saturated with a polymer and applied to the concrete surface by hand. This causes relatively large variation in properties of the cured FRP composite material. It is hard to know the exact mechanical properties of the FRP constructed by wet lay-up process. In addition, the stiffness of FRP changes during debonding process due to different amount of concrete attached to the debonded FRP at different locations. It is also inevitable to have considerable variations in the strength of concrete. Therefore, the behaviour of FRP bonded concrete members varies among specimens even when the same materials are used. The variation of localized FRP stiffness and concrete strength can be combined in a single parameter as variation of the localized interfacial fracture energy. In an effort to effectively model the effects of the variation of interfacial fracture energy on the load versus deflection responses of FRP bonded concrete specimens subjected to Mode I and Mode II loading, a random white noise using a one-dimensional standard Brownian motion is added to the governing equations, yielding stochastic differential equations. By solving these stochastic equations, the bounds of load carrying capacity variation with 95% probability are found for different experimental tests.

Sensitivity analysis of stress state and bond strength of fiber-reinforced polymer/concrete interface to boundary conditions in single shear pull-out test

“…10,23,24 For example, Figure 2 presents the local bond stress-slip relationships at different locations from the loaded end in a pull-out test reported by Dai et al 10 The large scatter of the bond-slip behavior may be due to the discrete nature of concrete cracks, random distribution of concrete aggregates, local FRP composites defects during the application of strengthening system in situ such as wrinkles and scratches, 25,26 and/or different concrete volumes attached to the FRP after initial damage affecting the stiffness of the debonding element. Mohammadi et al 27 used mathematical methods called white noise and Brownian motion to model the variation of the interfacial fracture energy and a systematic method was developed to predict the load capacity variation in FRP bonded concrete specimens.…”

Bond–slip behavior of fiber-reinforced polymer/concrete interface in single shear pull-out and beam tests

“…27,28 This large scatter of the bond-slip behavior may be due to local FRP composites defects in the application of strengthening systems in-situ such as wrinkles and scratches, 29,30 and/or possible heterogeneity of the concrete substrate. Mohammadi et al 31 showed a significant variation in the interface stiffness using the statistical Brownian motion in a stochastic method that may cause the variation in the FRP/concrete interface behavior.…”

“…Mohammadi et al. 31 showed a significant variation in the interface stiffness using the statistical Brownian motion in a stochastic method that may cause the variation in the FRP/concrete interface behavior.…”

Avaliação do efeito de escala nos valores de carga de colapso de interface entre concreto e polímero reforçado com fibra de carbono

“…Em relação aos sistemas apresentados anteriormente, Mohammadi et al (2015) afirmam que há uma grande variação nas propriedades dos compósitos de PRF preparados por via úmida. Nesses sistemas, as fibras secas são saturadas com resina e aplicadas manualmente na superfície do concreto.…”

“…Nesses sistemas, as fibras secas são saturadas com resina e aplicadas manualmente na superfície do concreto. De acordo com Mohammadi et al (2015), nesse caso, é difícil conhecer as propriedades mecânicas exatas do PRF, como por exemplo o módulo de elasticidade. Os autores destacam que, apesar dos fabricantes geralmente fornecerem as propriedades, em campo elas são afetadas por vários fatores, como o processo de cura e a existência de defeitos que podem ocorrer durante a instalação.…”