Effect of member depth and concrete strength on shear strength of RC deep beams without transverse reinforcement

•Eight RC deep beams without stirrups were loaded to shear failure.•The beam depth ranges from 200 to 1600 mm.•The test results indicate a significant shear size effect of the specimens.•A fracture mechanics based size effect coefficient was proposed for struts in STM.•Design shear models and mechanics based shear models were evaluated.