| Because of its excellence, the material of concrete has been widely used in civil engineering for many years. The concrete is a kind of nonlinear material made up of bone and sand slurry. Due to the process of molding concrete initial stage dryness and hydratability, there are a lot of initial cracks in the bone and sand slurry combination. Many studies show that the nonlinear of concrete is caused by these cracks crazing and expanding. The process of concrete damage is involved in a great deal of the microcosmic mechanism. At present, the advantage of the microcosmic mechanics to study the process of concrete damage and fracture is being noticed. Especially, the development of computer, it inaugurates the vast foreground to study the macroscopical mechanical problem from the mesoscopic mechanics.This paper is based on the understand of the concrete material. By introducing Weibull probabilistic distribution for heterogeneities of mechanical properties of concrete components, influence of heterogeneity of the components on the concrete strength is analyzed. An improved model is also presented by introducing spatial correlation length factor into Weibull distribution law. Effects of spatial correlation length on the concrete strength are studied.Besides, based on the moment-curvature relationship of beam section analysis method and conjugate beam method, numerical simulation analysis of concrete beams strengthened with FRP by using nonlinear finite element program in Fortran language, the results of load-displacement curve obtained can be in good agreement with the experimental results; Proposed a method to calculate the lagged strain, and compared with the existing methods, the results show that the calculation of this calculating method has higher accuracy; Derived the formula of bending bearing capacity of concrete beams strengthened with FRP, The calculated results compared with experimental results and numerical simulation results are approximate. |
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