Behaviour of CFRP wrapped RC square columns under eccentric compressive loading

Abstract

This paper presents the effects of carbon fibre reinforced polymer (CFRP) volumetric ratios on structural and failure behaviour of CFRP wrapped reinforced concrete (RC) square columns under concentric, eccentric and flexural loadings. The CFRP volumetric ratio is considered as the ratio of volume of CFRP to the volume of concrete. The applicability of existing confinement models to predict the load-moment interaction diagrams of such columns in eccentric loadings is also presented in this paper. Total 20 columns were tested. Dimensions of all columns were 175x175x800 mm with 20 mm rounded corners. Variable considered in this study were number of CFRP layers (e.g. 0, 1, 2 and 3 layers) which corresponds to CFRP volumetric ratio of 0, 0.3, 0.6 and 0.9%, respectively, increasing eccentricities (e.g. 0, 25, 35 and 50 mm) of the applied load and pure flexural loading. Results show that ultimate load capacity and axial deformation increase with increase in CFRP volumetric ratios irrespective of eccentricities. However, load capacity and deformation decrease with increasing eccentricities for any given CFRP volumetric ratio. Hoop strains also increase with increase in CFRP volumetric ratios and eccentricities. Stiffness of CFRP wrapped columns also increases with increase in CFRP volumetric ratio up to 0.6% and decreases with increase in eccentricities. Ductility of CFRP wrapped columns increases with increase in CFRP volumetric ratios and eccentricities. The algorithms for calculation of critical points for load-moment (P-M) interaction diagrams using analytical as well as numerical stress integrations are developed and compared to those of the column tests. P-M interaction diagram developed using existing confinement models agree well with the experimental P-M interaction diagrams of CFRP wrapped RC square columns under eccentric loading.