Condition Assessment Tool for Reduced Strength of Eccentrically Loaded Columns with Damaged FRP Wraps

Fiber-reinforced polymer (FRP) wraps of reinforced concrete columns might be vulnerable to accidental damage or vandalism. This study aims to develop a simple empirical tool that is based on experimental results to aid in the condition assessment and establish the reduced axial strength ratio (P/Po) of short columns that are loaded at small eccentricities. A total of 47 cylinders, 152 mm in diameter (D), were wrapped with carbon–FRP sheets of 1–3 layers [i.e., producing confinement effectiveness (fcc′/fc′) of 2.3–4.0] and were then subjected to a vertical cut of length (x) that varied from 0.20D to 0.61D at midheight. The loading eccentricity (e) varied from zero to 0.1D. The cut location around the perimeter, for the angle (θ) that was measured from the point of extreme compression, was varied from 0° to 180°. The jacket cuts affect eccentrically loaded cylinders more severely than concentrically loaded ones. As e increased from zero to 0.1D, P/Po reduced from 1.0 to 0.81 for intact samples and from 0.56 to 0.40 for samples with jacket cut. As the cut location traveled around the circumference starting from extreme compression (θ = 0°), less strength reduction was observed where P/Po increased, and at θ = 180° it even exceeded P/Po at zero eccentricity. This suggests a reduction in eccentricity due to a shift in the cross-sectional centroid due to the disturbed confinement on one side. Design models that account for e/D, θ, x/D, and inclined cuts have been developed and calibrated for cylinders of up to 22 slenderness ratio. In addition, a design example is presented.