Seismic retrofitting of coastal structural columns with steel bars locally corroded to fracture using sprayed ECC overlays and FRP jackets

The steel bars of coastal reinforced concrete (RC) columns have a high risk of being corroded to fracture, which would severely weaken their seismic performance and make them face necessary demolition. In this regard, this study attempted to retrofit such columns through sprayed engineered cementitious composite (ECC) overlays and fibre-reinforced polymer (FRP) jackets to restore their seismic performance without demolition. To prevent the asymmetry in the load–displacement response along opposite directions, planting steel bars at the locations of longitudinal bars fractured owing to corrosion was also carried out. Cyclic loading tests were performed on nine RC columns with the most severe corrosion until the longitudinal reinforcement fractured. The test results indicated that the ductility and energy dissipation capacity of the severely corroded columns using the proposed retrofitting schemes were even significantly superior to those of the non-corroded column: increased by up to 48.5 % and 57.5 %, respectively. The biaxial jacketing of FRP sheets could recover the seismic performance of the severely corroded RC columns without requiring the planting of rebars. Analyses on the variations in the plastic hinge length indicated that the proposed retrofitting scheme significantly improved the sectional rotation capacity of the corroded columns and thereby improving their deformation capacity.