Ahmet Abdullah DÖNMEZ, Lokman IŞIK
Shear failures of reinforced concrete sections are known to be a brittle type of failure which applies to sections when there are unusual lateral effects. Unfortunately, the real mechanism lying behind the shear failures of reinforced concrete sections has not been fully understood. Moreover, the discussions about the reinforced concrete beam shear among the communities have been continuing. The direct shear tests, which are based on the principles of structural mechanics, have been being conducted since the 1950s for better understandings. These tests conventionally are being called direct shear tests and are used to suppress the difficulties about the boundary conditions of a concrete member. Therefore direct shear specimens could be used to explain the shear behavior under axial loads. This study involves the direct shear tests of reinforced concrete sections. The size effect behaviors of these specimens were also investigated. The experimental results were verified with the numerical works using a realistic and calibrated material model. Results showed that the size effect is significant in these types of specimens. The size effect trend exhibited by the direct shear specimens is not only deterministic but also probabilistic type, which is known to be the size effect type 1. However, numerical works showed that the type 1 size effect trend drastically changes to the type 2 size effect as the specimen geometry and the loading conditions change. A slight inclination of the shear axis would lead to a shear force and axial load combined action on the section. The combined effect causes a variation in the source of the size effect and size effect trend. The modified size effect trend is compatible with type 2, which is the fully energetic type of the size effect. The obtained results can be used in shear capacity calculations of the reinforced concrete sections.

Anahtar Kelimeler: Direct shear failure, Size effect, Reinforced concrete sections, Shear strength