Nonuniform CFRP Wrapping to Prevent Sudden Failure of FRP Confined Square RC Columns

This is the first study on the effectiveness of nonuniform fiber-reinforced polymer (FRP) wrapping to strengthen and prevent the sudden failure of a square reinforced concrete (RC) column. The behavior and performance of square RC columns strengthened with nonuniform carbon FRP (CFRP) wrapping were critically investigated in comparison with the behavior and performance of square RC columns strengthened with full and intermittent CFRP wrapping. The results from the experimental study revealed that nonuniform wrapping enhanced the strength and improved the ductility of square RC columns. Also, nonuniform wrapping was effective in preventing the sudden failure of the FRP confined square RC columns. The strength enhancement of square RC specimens due to the nonuniform wrapping was higher than that due to the intermittent wrapping but lower than that due to the full wrapping when an equivalent amount of CFRP was used. The failure envelopes (axial load–bending moment interactions) were analytically developed for the test specimens. It was found that the analytical failure envelopes agreed well with the experimental failure envelopes.