Influence of size on fracture energy of concrete

Concrete structures frequently exhibit cracks. In order to investigate the influence of cracks on durability and the remaining load bearing capacity of buildings, fracture mechanics models can be used. For materials like concrete non-linear models for example the fictitious crack model introduced by Hillerborg, Modeer and Petersson or the crack band model proposed by Bazant and Oh are able to describe crack formation and propagation in a realistic way. But it has been observed, that the parameters of these models depend both, on structural size and geometry. In this paper a simple model to explain the nature of size and geometry dependence of the specific fracture energy is presented. The model is evaluated with experimental data from Trunk and Wittmann.