Synergistic Effects of CFRP and Steel Fiber in Slender RC Columns Under Eccentric Compressive Loads: Experimental and Predictive Analysis

This research addressed the compressive performance of slender reinforced concrete (RC) columns containing steel fibers and strengthened with carbon fiber-reinforced polymer (CFRP) under eccentric loading. Here, 12 slender RC columns were manufactured in four groups: plain concrete columns, plain concrete columns strengthened with CFRP, steel fiber-reinforced concrete (SFRC) columns, and SFRC columns strengthened with CFRP. Synergistic effects of steel fibers and CFRP sheets on the energy absorption level, load-carrying capacity, and curvature of the slender RC columns under eccentric compressive loads were investigated. The results demonstrated that using either CFRP sheets or steel fibers improved the eccentric compressive behavior of the slender columns. Moreover, the simultaneous use of steel fibers and CFRP sheets had the most significant effect on the performance improvement among all the experimental groups under the eccentric load. This performance improvement consisted of an increase in the displacement ductility, tangent stiffness, and longitudinal strain at failure with a decrease in the secant stiffness. In addition, increasing the eccentricity mitigated the effect of these two materials on the mentioned mechanical parameters. Finally, a formula was presented for predicting the load-carrying capacity of CFRP-wrapped slender RC columns containing steel fibers under load eccentricity.