Size-scale effects on plastic rotational capacity of reinforced concrete beams

A complete numerical algorithm that assumes a strain localization in concrete, both in tension and compression, is proposed for modeling cracking and crushing growths during the loading process of reinforced concrete beams in bending. With this algorithm based on nonlinear fracture mechanics models, it is possible to investigate the effects of the main mechanical and geometrical parameters on the rotational capacity with particular regard to the reinforcement percentage and the element size. A comparison with experimental results demonstrates the effectiveness of the proposed approach for a wide range of reinforcement percentages and beam depths. The obtained results show that the prescriptions concerning the admissible plastic rotations provided by the existing design formulas are not conservative in the case of large structural sizes. To overcome such a drawback, a new design diagram is proposed for practical purposes.