Study of the scale effect on diagonal crack propagation in concrete beams

Experimental investigation and numerical simulation have been performed in order to analyze shear capacity and the character of diagonal crack propagation in concrete beams reinforced longitudinally but without transverse reinforcement. The early investigation showed that the shear failure mechanism varied significantly, particularly as a function of a shear span-to-depth ratio. In this paper the scale effect is discussed, as test results indicate a strong influence of the member size as well. In analyzed beams the static scheme, concrete grade and longitudinal reinforcement were the same, whereas the effective length l eff , varied from 0.8 to 1.8 m. Significant differences were observed in the character of cracking and failure process between short beams of l eff = 0.8 and 1.0 m and longer beams of l eff > 1.0 m. To analyze the scale effect on the failure process in the beams, numerical simulation has been performed. In particular, a fracture mechanics study has been used to simulate the crack evaluation in two beams of different length but of the same shear span-to-depth ratio. Numerical results were compared with the experimental data.