Experimental Assessment of External and Internal Geogrid Confinement of Reinforced Concrete Columns

Abstract

The use of fiber-reinforced polymer (FRP) as an external column confinement and retrofitting material has been dominant. However, researchers have been experimenting other methods due to the FRP high cost. Recent research has shown the efficacy of Geogrid as a geo-synthetic material as an internal reinforced concrete column confinement. This study investigates experimentally the feasibility of using geogrid material as an external column confinement as compared to FRP and flexible bitumen coated E-glass textile. The test variables are transverse reinforcement spacing, confinement material (Geogrid, Bitumen coated E-glass textile, or FRP), type of geogrid (uniaxial or biaxial), number of confinement layers (one or two), and confinement location (internal or external). A total of 39 small-scale column specimens were tested under uniaxial compression. Assessment of the variable was done by analyzing the axial load-displacement behavior, the modes of failure, and the structural ductility measured by fracture energy and energy dissipation. Results show that the external confinement of reinforced concrete columns using geogrid can significantly enhance the strength, ductility, and energy capacity of the specimen. An analytical confinement model to predict the ultimate stress of the specimen using geogrid and bitumen textile was developed from existing confinement model for FRP. Comparison between the confinement stress model and the experimental results provided satisfactory predictions for the ultimate stress. This study provided promising results for the use of geogrid as an external confinement for reinforced concrete columns despite the fact that the tensile strength of the geogrid is significantly lower than that of synthetic FRP.