Size effect in torsional failure of concrete beams

The paper examines whether the size effect law for failures due to distributed cracking, recently derived from fracture mechanics arguments, is applicable to torsional failure of unreinforced or longitudinally reinforced concrete beams of rectangular cross section without stirrups. The test data available in the literature are used for this purpose. They confirm that a size effect is present and does not disagree with the size effect law. However, the data range is so narrow and their scatter so large that the precise form of the size effect cannot be identified. A simple, theoretically based formula to take the size effect into account is suggested.