Recent Studies of Size Effect in Concrete Structures

Recent advances in the size effect law for the failure stress of concrete specimens or structures and its application for the determination of fracture energy are reviewed and some extensions of the previous formulations are presented. One extension consists of a modified form of the size effect law which involves only true material parameters, particularly the fracture energy and the effective length of the fracture process zone. These parameters are both uniquely defined on the basis of the extrapolation of specimen size to infinity. This extension makes it possible to define the brittleness number of a structure in terms of an equivalent shape-independent structure size and the limiting length of the fracture process zone. The calculation of the brittleness number requires the value of the nondimensional energy release rate for the equivalent crack in an elastic structure, whose value and derivative take into account the shape of the structure. Another extension is the determination of R-curve from the size effect, and its use to calculate structural response