Evaluation of square slender RC columns subjected to eccentric loading strengthened with longitudinal FRP sheets based on PIV analysis

Abstract

In this study, the behavior of square slender reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets was investigated. The externally bonded reinforcement on grooves (EBROG) method as a new technique was employed to strengthen the specimens compared to the externally bonded reinforcement (EBR) method as the conventional strengthening technique. Twelve small-scale slender square RC columns (i.e., 125 × 125 × 900 mm) with a slenderness ratio of 25 were loaded under eccentricity-to-cross-section ratios (e/h) of 0, 0.24, 0.48, and 0.72. The results showed the EBROG's superiority over EBR in load-carrying capacity enhancement of the strengthened RC column specimens in various eccentricities; i.e., the loading enhancements were 10.6 to 99.3% for the EBROG specimens and 1.2 to 41.7% for the EBR specimens at varying eccentricities of 0 to 90 mm, compared to those of un-strengthened specimens. Furthermore, the moment capacity enhancement of the EBROG specimens was higher than that of the EBR columns; i.e., it was 100.0% for the EBROG specimens and 42.2% for EBR specimens in the eccentricity of 90 mm, compared with the un-strengthened specimen. Using particle image velocimetry (PIV) analyses, the results of flexural stiffness, strain distribution, ductility, and energy absorption were presented and discussed. Results revealed that by increasing the eccentricity, flexural stiffness decreases; this reduction was more intense for EBR specimens (42%) than the EBROG specimen (36%). An analytical procedure was conducted to compare the experimental and theoretical results. The analysis demonstrated good agreement between the results and the superiority of the EBROG method over the EBR.