Analytical model for prediction of load capacity of RC columns confined with CFRP under uniaxial and biaxial eccentric loading

This paper presents an analytical model for prediction of the load carrying capacity of reinforced concrete (RC) columns confined with carbon fiber reinforced polymers (CFRP) under uniaxial and biaxial eccentric loading. The model is based on realistic material laws and accounts for the non-linear stress-strain behavior of both unconfined and CFRP-confined concrete. Under uniaxial eccentric loading, the column cross-section is discretized into finite layers along the section depth. For a symmetric square cross-section subjected to biaxial eccentric loading with equal eccentricity about each principal axis, the column cross-section is discretized into finite layers along the diagonal of the column cross-section. For a given strain distribution in a direction perpendicular to the neutral axis, the sectional forces are integrated numerically and the load capacity of the column is predicted using an iterative process. For rectangular and non-symmetric square cross-sections subjected to biaxial eccentric loading, the load capacities under uniaxial eccentric loading along each principal axis are first derived independently. The column load capacity under concentric axial loading is calculated. The determined distribution of the column load capacities under uniaxial eccentric loading and concentric loading are then utilized to compute the load capacity under biaxial eccentric loading using the reciprocal load equation. An experimental study was carried out to examine the effectiveness of the CFRP-confinement to improve the load capacity and ductility of RC columns under biaxial eccentric loading. The accuracy of the proposed analytical model was demonstrated by comparing the model predictions to results of the current experimental study in addition to experimental data published in the literature.