Investigation of size effect in notched specimen with geometrically similar and dissimilar

The strength of laboratory-sized specimens is greater than the strength of structural members in real structures. In fracture mechanics, the reason for this is explained by the term of size effect. The size effect indicates that the strength of specimens with initial cracks decreases with increasing size. It is well known that quasi-brittle materials such as concrete show a size effect even if there is no initial cracking. Because concrete specimens, may include certain defects, such as voids and cracks, even before being exposed to loads. For this reason, this thesis research was conducted to understand the fracture behavior of specimens without initial cracks and to determine the effect of crack length to specimen depth ratio on the size effect law for concrete specimens without initial cracks. Size effect researches have been carried out on specimens with a similar geometry with fracture models, but experimental data showing the effect of size for dissimilar geometries and the same material are quite limited. For this purpose, geometrically similar and dissimilar test specimens were investigated. Concrete mixtures with aggregate grain diameters of 4, 8 and 12 mm were prepared in accordance with TS 802 standards. The water/cement ratio in the mixtures was designed as 0.6. In experimental researches, central, double edge and single edge notched specimens were produced. The specimens were designed with a thickness of 50 mm, at least three different depths and relative notch lengths. 12 series, 552 specimens were produced in different combinations. Also cube specimens were used in each batch for determining mechanical properties of concrete. At the end of the 28 days curing period, splitting, bending and compact compression tests were applied to the prepared specimens. Obtained data were analyzed using the popular size effect laws, in the literature fracture mechanics models and approximate formulas were developed. Size effect was observed in all specimens types and some approximate formulas were determined to be applicable.