Abstract:
CFRP (Carbon Fiber Reinforced Polymer) and GFRP (Glass Fiber Reinforced Polymer) are used to enhance the strength and ductility of concrete. The enhancement in strength and ductility depends upon the type of fiber reinforced polymer (FRP) used and also on the unconfined strength of the concrete. Since the present design guidelines have short comings in predicting the behavior of these polymers exactly so a comparative study is needed to identify an efficient FRP confinement for achieving enhancement in strength and ductility and predict its behavior more precisely. This research provides a comparative study of the behavior of confinement of GFRP and CFRP on normal and high strength concrete. These polymers were wrapped on circular concrete cylinders casted from three batches of concrete possessing axial strength of 30, 42 and 64 MPa. By doing so, different properties of FRP confined concrete have been observed such as the increase in strength, stiffness and ductility. These mechanical properties were compared to those of unconfined specimens and then correlated with American design guidelines (American Concrete Institute ACI 440.2R-08, Canadian Standards Association CSA S806-02 and Intelligent Sensing for Innovative Structures ISIS MO4-01) and European CEB/FIP Model Code 2010. The results indicated an increase in axial compressive strength of about 8.56 to 29.47 percent for GFRP confinement and 12 to 60.7 percent for CFRP confinement. The hoop strain of GFRP confined specimens increased from 1.13 to 2.64 times while CFRP confined specimens showed an increase of 1.22 to 5.4 times the hoop strain of unconfined specimens. Among the three guidelines, ACI showed closest results in all strength domains for both GFRP and CFRP confinement. ISIS guidelines gave conservative results as compared to ACI. CSA showed the most conservative results for both axial compressive strength and ultimate load carrying capacity and was unable to predict GFRP confinement of high strength concrete. This research will help in identifying the most suitable FRP to induce specified increase in strength and enhancement in ductility for reinforced buildings and infrastructure. This will also help in more predictable and efficient retrofitting of the concrete sections.
