Retrofit of PRC bridges by external post-tension under different corrosion scenarios

Prestressed reinforced concrete bridges with post-tensioned strands are subjected to heavy corrosion deterioration problems due to injection defects and chloride ingress by de-icing salts or sea airborne. The peculiarity of this prestressing system is recognized by the new italian guidelines on existing bridges prescribing special assessment procedures. Therefore, these bridges need reliable strengthening techniques able to enhance durability reducing the risk of collapse. This paper examines the application of post-tension to rehabilitate pc bridges with injected cables, considering corrosion initiation and propagation, estimated through a chloride ingress model included in the finite element models. Assuming a high chlorides surface concentration, a case study bridge is investigated to design an external post-tension intervention evaluating the time evolution of the capacity-demand ratio under gravity and traffic loads. The capacity loss is estimated depending on the considered corrosion period also assessing the response in terms of cracking and deformation.