Confinement of concrete cylinders using dry glass fiber hoops: Experimental investigation and analytical modeling

This study presents an experimental investigation into the use of dry glass fiber hoops for externally confining cylindrical concrete specimens. Various fiber configurations, including different fiber areas and lateral spacings, were applied to assess the confinement effects on the axial and lateral behavior of the concrete under compression. The specimens were subjected to axial compression tests, during which axial force, axial strain, and lateral strain were recorded. The axial stress-strain response demonstrated two distinct behaviors depending on the level of confinement, with higher levels of confinement resulting in substantial increases in both strength and ductility. The strength and corresponding axial strain were found to increase proportionally with the level of confinement, significantly exceeding the performance of unconfined concrete. A comparative analysis highlighted that dry glass fiber hoops provided competitive confinement efficiency relative to FRP sheets and hemp ropes, particularly in terms of strength and ductility. The study also introduced an analytical model to predict the stress-strain behavior of confined concrete using dry fibers. This model successfully captured key points such as peak axial strength, corresponding axial and lateral strain, and ultimate axial strain, showing strong correlation with the experimental data. Compared to traditional FRP jacketing, this innovative confinement method offers advantages such as ease of application, cleaner construction, and no need for epoxy adhesives, making it a promising alternative for structural retrofitting and strengthening.