In most of the structural members with initial cracks, the strength tends to decrease as the member size increases. This phenomenon is known as size effect. Among the structural materials of glass, metal or concrete, etc., concrete represents the size effect even without initial crack.
According to the previous size effect law, the concrete member of very large size can resist little stress. Actually, however, even the large size member can resist some stress if there is no initial notch. This means that the fracture mechanism of very small or very large size member follows strength criterion, but the medium size member follows non-linear fracture mechanics (NLFM).
In this study, the previous size effect law for concrete proposed by Z.P. Bazant is explained, followed by a discussion on the size effect law for concrete without initial notch together with the proposed basic formula. Finally, the empirical models are proposed according to the regression analysis with the test data of large size specimen by other investigators.
