The Application On Concrete Of Fracture Mechanics And Size Effect

With the development of concrete structure, more and more important buildings were constructed. The secure and normal operation is not a mere problem of technique or economic but one having great impact on welfare of the people and stability of the .society. However, these structures were usually high and complicated, endured big and variational load, and encountered abominable environment and accident. The mechanic analysis and design of the structures required enough precision and reliability, but it is very difficult theoretically and practically.In addition, concrete is uneven, unlinear and anisotropic because of its complicated composition. The existence and development of pre-crack , the variety of the mechanic performance and environment result in the complicated strength and strain. So that, the performance parameters are discrete, variational and influenced by many factors.In the past, reinforced concrete structures were usually small and simple so that we could make the experiments with the real size or small-scale model to get the mechanic performance of the structures. And the test results could be directly applied to the structure design and analysis. But this method could not be applied to the huge and complicated structures. The application of fracture mechanics to concrete research greatly promoted the development of concrete fracture mechanics and strength theory. However, not only linear elasticity but also elasticity-plasticity fracture mechanics had each limitation when they were applied to concrete research.This paper reviewed classic concrete strength criterions, discussed the merit and defect of every above-mentioned criterion and brought the necessity of extended research. In succession, this paper discussed the important phases of fracture mechanics, as well as the application of fracture mechanics to concrete. Based on thecompare and analysis of two kind of Bazant size effect, the predominance of energy method was pointed out. In the end, on the basis of considering the boundary effect, a new local fracture energy distribution model and the corresponding formulation were established.