GENERALIZED SIZE EFFECT EQUATION FOR QUASIBRITTLE MATERIALS

Structures made of quasibrittle materials show a marked decrease in st rength as their size increases; this is the well known size effect on strength. This contribution proposes a general formula to predict with great accuracy the size effect of pre-cracked specimens. Such a formu la provides the basis to determine experimentally the fracture paramet ers of a cohesive crack model from the measurement of the peak load in specimens with an initial crack. The formula is applicable whenever t he fracture of the material can be described by a cohesive crack model with initial linear softening, as is generally accepted for concrete. Experimental evidence is presented showing that the formula is reason ably accurate also for rock.