Experimental investigation of load carrying capacity of the slender reinforced concrete columns wrapped with FRP

Axial compression test was conducted on 6 elliptical modified rectangular slender reinforced concrete columns wrapped with FRP, with a slenderness ratio L/b ranging between 4.5 and 17.5. The test result showed that the effect of the slenderness ratio on the load carrying capacity of FRP-wrapped concrete columns is more significant than that of ordinary reinforced concrete columns. The strengthening effect decreases with increase of the slenderness ratio. When the slenderness ratio is less than 17.5, the load carrying capacity of FRP-wrapped columns is still 20% higher than that of ordinary reinforced concrete column. The columns were then successfully analyzed with the commercial finite element software ANSYS, taking into account of the constitutive relationship of concrete reinforced with FRP, the failure criterion and the initial geometrical imperfections. The effect of the cross-sections, steel ratio and the confinement ratio is investigated and a simplified formula for the stability coefficient to facilitate design of FRP-wrapped columns is derived.