Experimental evaluation of energy dissipation and viscous damping of repaired and strengthened RC columns with CFRP jacketing under biaxial load

•8 RC columns tested under biaxial load, repaired and retrofitted with CFRP sheets.•Efficiency of the retrofit was evaluated in terms of energy dissipation and equivalent viscous damping.•The repair strategy restored the energy dissipation capacity of the damaged columns.•The use of CFRP jacketing improved the energy dissipation for larger drift demands. The seismic repair and retrofitting of reinforced concrete (RC) columns have been the focus of innumerous studies and from the literature it can be concluded that the biaxial horizontal loading can reduce considerably the strength capacity, ductility and energy dissipation of the columns when compared with the corresponding response to uniaxial loading tests. However, reduced information regarding the influence of the retrofit strategies in the energy dissipation capacity and the viscous damping of the columns were obtained. Thus the main goal of the present work is to evaluate the efficiency of the Carbon Fiber Reinforced Polymer (CFRP) jacketing technique to improve the behaviour of three damaged columns subjected to repair procedures and four “as built” columns behaviour and evaluate their influence in the energy dissipation capacity and viscous damping of the columns when compared with the original response. From the test results a good efficiency of the CFRP jacketing improved about 20% the original energy dissipation capacity. Regarding the viscous damping it was obtained about 10% lower values for the repaired columns and to 20% higher values for the strengthened ones.