FRCM confinement as a repair technique for seismically damaged RC columns

The research work deals with the experimental behavior of undamaged reinforced concrete (RC) columns and seismically-damaged repaired RC columns under increasing cyclic lateral loading. Two real-scale elements were initially tested under constant axial and increasing cyclic lateral loading to simulate a seismic damage. A repair protocol, designed to restore the initial strength of the elements, was then followed. Based on the initial damage observed on the specimens, two repair methods were adopted: for damage concentrated only in the concrete, column base was confined through fabric reinforced cementitious mortar (FRCM), while, for damage also extended to the bending steel reinforcement, additional FRCM flexural reinforcement was embedded in the confinement jacket. Results of undamaged and repaired specimens are presented and compared in terms of cracking pattern, load-displacement curves, ductility, stiffness degradation and energy dissipation. During the loading history, fiber strains were monitored in the repaired columns through electrical strain gages previously installed in the fabric. The experimental results show that FRCM composites can be effectively used to restore strength and ductility of RC columns previously damaged by cyclic lateral loading.