Improvement in the plastic rotation evaluation by means of fracture mechanics concepts

The well-known Cohesive Crack Model describes strain localization with a softening stress variation in concrete members subjected to tension. Based on the assumption that strain localization also occurs in compression, the Ovelapping Crack Model, analogous to the cohesive one, is proposed to simulate material compenetration due to crushing. By applying this model, it is possible to describe the size effects in compression in a rational way. The two aforementioned elementary models are then merged into a more complex algorithm based on the finite element method, able to describe both cracking and crushing growths during loading processes in RC members. With this algorithm in hand, it is possible to investigate on the influence of the reinforcement percentage and/or the structural size of RC beams, with special attention to their rotational capacity. The obtained results evidence that the prescriptions concerning the plastic rotations provided by codes of practice, not taking into account the scale effects, are not conservative in the case of large structural sizes.

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