Seismic behavior of damaged RC columns repaired with FRCM composites

In literature, a limited number of studies were carried out on the use of externally bonded composites to repair reinforced concrete (RC) columns subject to cyclic increasing lateral loads. Among them, very few deal with the use of fiber reinforced cementitious matrix (FRCM) composites. Thus, this work experimentally analyzes the behavior of two real scale RC columns repaired through FRCM with carbon fibers, subject both to axial and lateral loads, the latter applied through fully-reversed increasing cycle steps. The goal of the repair interventions was to restore the initial strength and ductility of the specimens after severe damage was applied to the original columns. Two repair methods were adopted: in one case, concrete confinement at the column base was realized; in the second case, other than confining jacket, flexural reinforcement was also used. Cracking pattern, loaddisplacement curves, ductility, stiffness and strength deterioration, energy dissipation and curvature development along the plastic hinge zone were investigated, comparing the performance of the control specimens with the repaired ones. Results were also compared with ones obtained applying a simple analytical model. Fibers exploitation was experimentally monitored in the repaired columns. Results demonstrate that FRCM confinement jackets can adequately repair seismically-damaged RC columns, restoring the initial lateral load capacity. Repaired columns showed also a similar ductility and energy dissipation compared to the undamaged control ones, while damping ratio resulted slightly lower for the repaired columns.