Pseudo-Ductility Through Progressive Failure of Multi-Layered Carbon-Fiber-Reinforced Polymer (CFRP) Prestressed Concrete Beams

Abstract

The design codes/standards recommend using an over-reinforced beam section for FRP-reinforced structures to use the ductility of concrete to give adequate warning prior to complete failure. In contrast, the present study is based on the nonlinear response prediction of beams prestressed with carbon-fiber-reinforced polymer (CFRP) tendons and designed under-reinforced. The beam is designed here such that a progressive rupture of the CFRP tendons occurs, i.e. they rupture one after the other, introducing a kind of pseudo-ductility, which is enhanced owing to the additional inelastic energy resulting from the sequential rupturing of the tendons. A parametric study has been conducted on CFRP-prestressed concrete beams with different numbers of tendon layers, varying prestressing ratios and several cross sections moreover, a sacrificing warning rebar has been introduced for improving the ductility further. The findings showed that the prestressed concrete beam with multiple layers of CFRP tendons resulted in an improved ductile design as compared to the single-layered system. Additionally, grading of concrete in the beam section has been made to compensate for the reduction in the load-carrying capacity due to the layering of tendons. The pseudo-ductility of such functionally-graded beams has been found to be improved, with energy ratios as high as 78.7% and having comparable load-carrying capacity.