Experimental investigation into the behaviour of high slender concrete columns reinforced with CFRP and subjected to cyclic eccentric compression

Abstract

The current research investigates the application of carbon-fiber reinforced polymer (CFRP) composites, with different fibers orientations, for enhancing the compressive strength, the ductility and the specific cyclic characteristics of very slender ($\lambda$ = 29) square reinforced concrete columns, under cyclic eccentric compression load. An experimental research was carried out by testing seven identical reinforced concrete columns, differently reinforced by a composite of carbon fibers. The columns are 1600 mm in of height, and 55 mm² in section. They were subjected to a double-eccentric monotonic cyclic compression, until failure. For this purpose, in addition to the control column (C0), the fibres are arranged transversely, in the form of one, two and three CFRP layers, respectively on the three columns C1, C2 and C3 and they are arranged longitudinally on one column (L1). On another one (C45L45), the fibres are arranged at ±45° from the column axis. On the last column (L1C1), the reinforcement is of one layer with the fibers arranged transversely on another CFRP layer with the fibers arranged longitudinally. Load–displacement and bending moment–curvature have been analyzed to highlight changes in term of peak load; ultimate displacement; rigidity degradation; ductility factor of the curvature; evolution of the residual displacement; energy dissipation capacity; and damage index. It should be noted, that the different types of CFRP strengthening used, generally improved the behavior of the columns tested. Nevertheless, this improvement is highly dependent on the orientation of the CFRP fibres. The results show that in the columns (C1, C2 and C3) strengthened with transversal FRP fibres, the load-carrying capacity enhancements are of 14, 33, 24% relative to the one of the control column, and 21, 24, 28% respectively for the columns C45L45, L1 and L1C1. The results show that the reinforcement of columns L1 and L1C1 did not have a significant effect on the ductility of the curvature; on the contrary, the effect is negative. The most important enhancement is on the C45L45 column, which reached 139%. For the C1 C2 and C3 columns, the increase is respectively 12, 22 and 46%.

Keywords:

• Reinforced concrete
• slender column
• strengthening
• CFRP
• cyclic load

Disclosure statement

No potential conflict of interest was reported by the authors.