Effectiveness of strengthening by CFRP on behavior of reinforced concrete columns with respect to the buckling instability

The use of composite materials in the field of construction, such as, materials fully incorporated in the design, or as a means of strengthening after realization do not cease growing, particularly in reinforced concrete structures. Nevertheless, the result of the association between the strengthened reinforced concrete structure and the strengthening itself is not fully known. Our contribution in this field is an experimental research work, which consisted in studying the strengthening contribution on reinforced concrete columns in the objective to reduce the geometric instability caused by the slenderness effect. In the present case, the strengthening act consists of gluing a carbon fiber fabric around the columns using an epoxy adhesive. The required effect depends on the fibers orientation, for this purpose, three columns with various fibers arrangements were considered in addition to the control one (un-strengthened column). The four columns studied, have a square section and slenderness λ = 100, tested under a doubly eccentric compressive load. The results obtained are illustrated by: load–displacement, bending moment–curvature and bending moment-axial force responses. The obtained results indicate that strengthening using carbon fiber composites has a positive effect on the general behavior of reinforced concrete columns. Also, it shows that the CFRP envelope is efficient in improving the stability of strengthened columns with variable degrees according to the orientation of these fibers.