Strains in steel bars of reinforced concrete elements subjected to repeated loads

Abstract

To evaluate the strains in a steel bar of a reinforced concrete structure under repeated loads, a mechanical model is proposed. More precisely, a reinforcing bar embedded in a concrete cylinder subjected to uniaxial actions is modelled. In the proposed one-dimensional approach, both the nonlinear fracture mechanics of concrete and the bond-slip between the two materials are taken into account, since they affect the structural response of several reinforced concrete structures in the serviceability conditions and in the ultimate limit state. When cyclic actions are applied and previous cracks close up again, the interaction between the fictitious crack model of concrete in tension and the bond-slip near the crack is investigated. During the unloading phase of each cycle, only through refinement of the damage effects, with regard to the classical bond and cohesive models, can the hysteretic behaviour of the reinforced concrete structures be modelled. The strains in the bar, computed with the proposed model, seem to be in good agreement with those measured in the tests made by Bresler and Bertero.