Behavior of RC Columns Confined with CFRP Sheets and Subjected to Eccentric Loading

摘要

Reinforced concrete (RC) rectangular columns with aspect ratio of approximately 1.5 and externally confined with bonded carbon fiber reinforced polymers (CFRP) sheets were experimentally subjected to eccentric compression loads up to failure. The effect of the value of eccentricity and confinement configuration (fully confined (FC) and partially confined (PC)) on the behavior of the strengthened columns was studied. The experimental results showed that both strength and ductility of the strengthened columns had been improved with respect to the behavior of the reference columns. The improvement in column compressive strength of both FRP- confinement systems applied under eccentric loading was so pronounced as for that under concentric loading. Furthermore, an analytical study was conducted aiming to apply models proposed by the ACI guidelines for strengthening concrete structures with FRP (ACI 440.2R-02 and ACI 440.2R-08) to evaluate the enhancement of the strengthened columns. To overcome the well-defined weaknesses of applying these models, a simplified analytical form is proposed to assess the enhancement in column strength under the effect of eccentric loading. The proposed analytical model showed an agreement with the constructed theoretical axial force-moment (P-M) interaction diagram for FRP-confined concrete using ACI 440.2R-08. Ultimately, the proposed model provides a reasonable approach for evaluating the increase in the strength of eccentrically loaded fully or partially confined RC columns.