The cracking phenomenon and the consequent slip between rebars and concrete, characterize the behaviour of reinforced concrete structures. This is clear both in bending and in tension members, during serviceability and ultimate stages. The mechanical response of ties and beams can be reproduced by means of smeared cross-sectional models, founded on suitable constitutive relationships of materials. Due to the practical impossibility of an univocal definition of the crack pattern evolution, results of smeared approaches are affected by uncertainties. In order to evaluate the effect of the possible distances between the cracks, a new mechanical model is proposed. By taking into account the nonlinear fracture mechanics of concrete and the bond-slip between steel and concrete, a 'range' of tension stiffening is evaluated. For cracked reinforced concrete element in tension, the load-average steel strain curves, experimentally measured before and after the yielding of rebars, are contained in the proposed 'range'. The good agreement between theoretical and experimental results also persists in specimens having the same percentage of reinforcement, but different types of fibre reinforced mixture.
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