Repair of reinforced concrete bridge columns subjected to chloride-induced corrosion with UHPFRC

The rehabilitation of reinforced concrete (RC) bridge columns subjected to chlorideinduced corrosion is addressed in the present paper. The proposed strategy is based on the replacement of the original external layer made of normal-strength concrete (NSC) with ultra-high performance fiber reinforced concrete (UHPFRC), and it additionally involves the substitution of the existing corroded longitudinal reinforcement with new machined steel rebars. This repair technique aims at restoring strength, stiffness and ductility of the original column in a short time without altering its crosssection dimensions. Because of the high compactness of the UHPFRC, it also serves at improving the durability. The main contribution of the present work is a numerical investigation carried out in order to identify how the design decisions about the repair strategy influence the behavior of the restored column. The parametric investigation reveals that the length of the zone in which NSC is replaced by UHPFRC as well as the machined index (i.e., ratio between turned and original rebar crosssection area) must be properly selected to make the intervention effective. Numerical results also highlight that the main design issue to deal with is the relocation of the plastic hinge from the repaired zone towards the weak unrepaired part of the column. Practical design recommendations are finally formulated.