Stress-strain relationship of FRP confined concrete columns under combined axial load and bending moment

The stress-strain relationship of FRP confined concrete columns under eccentric loading is different from that under concentric loading. However, eccentric loading can have different load paths, e.g. constant axial force with increasing load eccentricity or constant load eccentricity with increasing axial load. The effect of different load paths on the stress-strain behavior of eccentrically loaded columns has remained unclear to date. It was believed previously that such difference in load paths could be insignificant for the stress-strain behavior of FRP confined concrete columns under eccentric loading. Unexpectedly, the study in this work on two different load paths demonstrates that the stress-strain behavior can be very different. A new stress-strain model for FRP confined circular concrete columns under constant axial force and increasing load eccentricity is developed in this work for engineering applications.