Fiber Reinforced Polymer (FRP) Confined Circular Concrete Columns: An Experimental Overview

Fiber-reinforced polymers (FRPs) are widely used as composite materials in civil engineering applications to rehabilitate or strengthen reinforced-concrete structural elements. The purpose of this study was to compile an extensive and up-to-date experimental database based on the compressive tests conducted on circular confined concrete structural elements using FRP composite materials. Strict criteria were implemented during the collection of the experimental data to minimize uncertainty and maximize uniformity. In order to compare the results, the collected data were divided into two categories based on the type of confinement, namely FRP wrapped and FRP tube encased. A detailed database of 1470 experimental test results on FRP-confined concrete cylindrical specimens demonstrated the specimens' geometry, the jacketing materials' physical and mechanical properties, and the effect of the confinement on the axial compressive strength and strain. The analysis of the database led to important observations on the parameters that influence FRP-confined concrete's behavior. The unconfined concrete strength seems to be inversely related to the confinement efficiency. The confinement efficiency is quite limited in high-strength concrete specimens. Carbon fibers tend to provide greater confinement effectiveness, while the FRP axial rigidity was found to contribute significantly to the effect of confinement. Glass and aramid fibers seem to perform equally well, regardless of the confinement method. An interesting finding is that while FRP-wrapped specimens perform similarly to tube-encased specimens in terms of increases in compressive strength, the latter are associated with larger increases in ultimate axial strains.