External Prestressed Carbon Fiber-Reinforced Polymer Straps for Shear Enhancement of Concrete

TLDR

The use of fiber‑reinforced polymers for concrete strengthening is well established, especially for flexural applications, and recent work has begun to explore their potential for enhancing shear capacity. The study investigates using posttensioned, nonlaminated carbon‑fiber‑reinforced polymer straps as external shear reinforcement for concrete. Experiments compared an unstrengthened control beam with beams reinforced by external CFRP straps. The strengthened beams exhibited significantly higher ultimate load capacity than the control, yet existing design codes underestimated both the control and strengthened beams’ resistance, while the modified compression field theory clarified failure mechanisms and the effect of strap prestress, supporting the viability of these stressed elements for durable concrete strengthening.

Abstract

The use of fiber-reinforced polymers (FRPs) for the strengthening and repair of existing concrete structures is a field with tremendous potential. The materials are very durable and, hence, ideally suited for use as external reinforcement. Although extensive work has been carried out investigating the use of FRPs for flexural strengthening, a fairly recent development is the use of these materials for the shear strength enhancement of concrete. The current system investigates the use of posttensioned, nonlaminated, carbon fiber-reinforced polymer (CFRP) straps as external shear reinforcement for concrete. Experiments were carried out on an unstrengthened control beam and beams strengthened with external CFRP straps. It was found that the ultimate load capacity of the strengthened beams was significantly higher than that of the control specimen. Existing design codes and analysis methods were found to underestimate the ultimate resistance of the control specimen and the strengthened beams. Nevertheless, the modified compression field theory provided insight into possible failure mechanisms and the influence of the strap prestress level on the structural behavior. It is concluded that the use of these novel stressed elements could represent a viable and durable means of strengthening existing concrete infrastructure.