The present article deals with the analysis of experimental results, in terms of load-carrying capacity and strain, obtained from tests on plain- and reinforced-concrete (RC) cylinders strengthened with external carbon-fiber-reinforced polymer (CFRP). The parameters considered are the number of composite layers and the compressive strength of unconfined concrete. The effective circumferential FRP failure strain and the effect of the effective lateral confining pressure were investigated. In total, 30 cylinders were subjected to axial compression, which included control specimens. All the test specimens were loaded to failure in axial compression and the behavior of the specimens in the axial and transverse directions was investigated. Test results showed that the CFRP wrap increases the strength and ductility of plain- and RC cylinders significantly. A simple model is presented to predict the compressive strength and axial strain of FRP-confined columns.

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Abstract. The behaviour of fibre reinforced polymer (FRP)-confined concrete in circular columns has been extensively studied, but much less is known about concrete in FRP-confined square columns, in which the concrete is non-uniformly confined and the effectiveness of confinement is much reduced. The present paper deals with the analysis of experimental results in terms of load-carrying capacity and strains, obtained from tests on square prismatic concrete column, strengthened with external glass fibre composite. The parameters considered are the number of composite layers and the corner radius for a square shape. A total of twenty-one prisms of size 100 × 100 × 300 mm were tested under strain control rate of loading.

The near surface mounted technique has been used in recent years for the strengthening of reinforced concrete beams. It involves the insertion of strips or rods of carbon fibers reinforced polymers in grooves made previously in the concrete cover of corresponding surfaces, filled with epoxy adhesive for fixation. A parametric study was carried out based on pullout-bending tests in order to evaluate the influence of bond strength, concrete strength, bond length, type and configuration of strengthening on the pullout load, bonding stress, stiffness and failure mode. The influences of these parameters on the bond behavior between the three materials (concrete, epoxy adhesive and carbon fibers reinforced polymer) were evidenced and discussed.

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