Behavior of GFRP Wrapped RC Columns of Different Shapes

Abstract

Abstract In recent years, the use of externally bonded fiber-reinforced polymers (FRP) has become increasingly popular for civil infrastructure applications. The Glass fiber reinforced polymer has significantly enhanced the strength and ductility of concrete by forming perfect adhesive bond between concrete and the wrapping material. Present experimental investigation mainly emphasises on effectiveness of external GFRP strengthening for RC Columns of circular, square and rectangular shapes having same cross sectional area. Total 15 RC columns of 1 meter in height were cast. 9 columns were control and the rest 6 columns were strengthened with one layer of GFRP wrap having 20 mm of corner radius. Columns were designed using IS: 456:2000 provisions. Design of GFRP wrapping was done using ACI 440.2R.08 provisions. All the test specimens were loaded to fail in axial compression and strain of the columns in the axial direction was investigated. The test results clearly demonstrated that the axial load carrying capacity increases from rectangular to square to circular shape of confined RC columns. No major impact on axial compressive strength is observed due to variation in shape for control columns, on the other hand, quite opposite behaviour was observed in case of RC columns confined by GFRP. GFRP wrapped circular column undergone more axial deformation as compared to that of square and rectangular columns. Stress-strain behaviour revealed that the strength gained from FRP confinement was prominent for circular columns. Square and rectangular-section columns are found to experience lesser increment in strength as compared to that of circular columns. This behaviour may be attributed to variation in lateral confining pressure distribution for rectangular columns from a maximum at the corners to a minimum in between, which is in contrast to even confining pressure observed for circular columns in order to achieve the full confinement effect.