Cyclic stress-strain model for large-rupture strain fiber-reinforced polymer (LRS FRP)-confined concrete

Abstract Large-rupture strain (usually larger than 5%) fiber-reinforced polymer (LRS FRP) composites are attractive materials for the seismic retrofit of concrete structures. Jacketing LRS FRP on concrete columns can effectively improve the ultimate strength and deformation of concrete structure and make the concrete structure have excellent ductility and superior energy absorption capacity. In comparison with conventional FRP, the concrete under LRS FRP confinement experiences a more severe damage process when it is under larger deformation. The confining pressure at the large deformation would alter the concrete plastic flow and significantly affect the cyclic stress-strain path of LRS-FRP confined concrete. This study evaluates the performance of existing cyclic models (e.g., unloading path, reloading path, and plastic strain) using a database including both traditional and LRS FRP-confined concrete. Through an analytical study on the cyclic response of LRS FRP-confined concrete, two key parameters (plastic strain and stress degradation) were found to influence the cyclic behavior of LRS FRP-confined concrete significantly. By defining these two critical parameters, a new cyclic stress-strain model was developed to LRS FRP confined-concrete with good performance. The proposed cyclic model was also applicable in predicting both post-peak strain hardening and softening behavior when used in a stiffness-based envelope model.