Safety assessment in N-M-V interaction of prestressed concrete elements subject to degradation of the reinforcements

The estimation of residual life of viaducts and bridges is urgently topical, due to the age of Italian infrastructure network. Among the causes of reduced life of prestressed concrete structures, the role played by corrosion in prestressed reinforcements is fundamental. In fact, the reduction of the reinforcement cross-section with the formation of the outer layer of iron oxides and hydroxides and the bad filling of the ducts, induces an intermediate behaviour between that of external (unbonded) and internal (bonded) prestressing. For these reasons, the evaluation of degradation and its influence on structural safety cannot be neglected in the assessment of sections of existing structures considering the interaction between the N-M-V stresses. In this paper, a methodology is proposed for cross section checking through interaction domains and an application to an emblematic study case is shown: the deck sections of the bridge over the Polcevera in Genoa