Retrofitting of reinforced concrete columns using near-surface-mounted steel rebars and fiber-reinforced polymer straps under eccentric loading

Abstract

This experimental study focuses on the retrofitting of reinforced concrete columns subjected to axial compression loading with different eccentricities. The proposed hybrid retrofitting technique incorporates two components: near-surface-mounted longitudinal steel rebars and transverse carbon-fiber-reinforced polymer straps. The latter was implemented to preclude buckling of the near-surface-mounted steel rebars under compression, to postpone debonding of near-surface-mounted steel rebars, to increase shear capacity of columns, and to improve the confinement level of concrete. The efficiency of the adopted retrofitting technique was evaluated through experimental testing of undamaged and damaged columns. Toward this, a total of 20 small-scale reinforced concrete circular columns including 5 control, 5 repaired, and 10 strengthened specimens were tested. All specimens were built to be identical with a diameter of 150 mm and a height of 500 mm. The specimens were tested under pure compression, combined axial–flexural (with eccentricities of 30, 60, and 90 mm), and four-point flexural loadings. Comparison of the results showed the efficacy of the proposed retrofitting strategy in enhancing the structural performance of both the undamaged and damaged columns in terms of loading capacity, ultimate displacement, and ductility factor. Finally, the axial load–bending moment interaction curves were discussed for all the tested columns.