Effect of fiber orientation and ply mix on fiber reinforced polymer-confined concrete

This paper explores the effects of fiber orientation and ply mix on load-deformation behavior and failure modes of fiber reinforced polymer (FRP) confined concrete by testing under uniaxial compression a designed array of plain concrete cylinders wrapped with different fabric orientation. Depending on the jacket confinement stiffness, either a strain hardening or a strain softening behavior was observed beyond the kink point where there was a sharp reduction in slope in the load-deformation curve. Kinking was seen to have a definable graphical relationship with the critical concrete lateral strain while the kink stress was found to upshift with increasing jacket stiffness. It is concluded that while hoop fiber wrapped concrete leads to brittle failures, angular fiber wrapped concrete tends to fail in a ductile manner, attributed to a fiber reorientation mechanism. Ply mix sequence plays an important role in the overall deformation and failure behavior. Existing models are found to be adequate in describing load-deformation behavior of angular fiber wrapped concrete as long as equivalent FRP properties in the hoop direction are used.