Effect of Geometric Discontinuities on FRP Strain Efficiency in FRP-Confined Circular Concrete-Filled Steel Tubes

The confinement of concrete columns using FRP jackets/wraps has become a popular retrofitting technique. More recently, the benefit of FRP confinement of concrete-filled steel tubes has been also explored by researchers. Failure of such FRP-wrapped concrete-filled steel tubes is usually governed by rupture of the FRP in the hoop direction. However, the observed FRP hoop strain at failure is typically lower than the ultimate strain in a flat coupon test. Many factors contribute to this phenomenon, one of which is the geometrical discontinuities at the ends of FRP wraps. This paper examines the effect of these geometrical discontinuities on the hoop rupture strain of FRP wraps. Detailed finite element (FE) analyses conducted using both linear elastic and elastic-perfectly plastic adhesive constitutive models are presented. Comparison between the FE predictions and available test results shows that the strain efficiency predicted by FE analysis using an elastic-perfectly plastic adhesive model are in reasonable overall agreement with the test results.