Behavior of FRP-confined high-strength concrete under eccentric compression: Tests on concrete-filled FRP tube columns

Accurate modeling of the complete stress-strain relationship of confined concrete is of vital importance in predicting the structural behavior of confined concrete columns under combined axial compression and bending. Although the axial stress-strain behavior of confined concrete under concentric loading is well established, the behavior under eccentric loading when axial and bending loads are combined is not well understood. This paper presents an experimental study on the behavior of carbon fiber-reinforced polymer (FRP)-confined high-strength concrete (HSC) columns under eccentric compression loading. 31 short concrete columns with circular and square cross-sections were tested under compression with different load eccentricities. The equivalent axial stress-strain curves of FRP-confined HSC under eccentric loading are obtained through sectional analysis conducted on the recorded experimental data. The results indicate that load eccentricity significantly affects the axial stress-strain behavior of FRP-confined HSC. In both circular and square cross-section specimens, an increase in the load eccentricity results in an increase in the ultimate axial strain but a decrease in the second branch slope of the axial stress-strain curve, which translated to a reduced ultimate axial stress in the specimens of the current study. The analysis of the results has shown that the ultimate axial strain increased and ultimate axial stress and second branch slope of the axial stress-strain curve decreased almost linearly with increasing eccentricity.