Concentrically Loaded Circular RC Columns Partially Confined with FRP

Wrapping reinforced concrete (RC) columns with fiber reinforced polymer (FRP) composites is effective in increasing their capacity. The current state of the art concentrates primarily on fully wrapped columns and few studies dealt with partially wrapped ones. The objective herein is to evaluate the effectiveness of partial wraps (or strips) and to develop a confined concrete compressive stress–strain (f_c − ε_c) model that accounts for partial wrapping. Three-dimensional finite element (FE) models are generated to evaluate the influence of different parameters on the behavior of concentrically loaded RC circular columns that are partially and fully wrapped with FRP. The results indicated an increase in ductility as the number of FRP strips is increased, and revealed that longitudinal steel had little influence on the confined f_c − ε_c relationship. The proposed f_c − ε_c model, derived from the parametric study, accounts for the effect of partial and full confinement, the unconfined concrete strength fc′, and yielding of transverse steel. Comparison of the results generated using the proposed model with FE and experimental results are in good agreement.