Numerical Analysis of CFRP Partially Confined Square Reinforced Concrete Column under Eccentric Loading

The use of fiber reinforced polymers (FRP) jackets as an external technique to strengthen existing reinforced concrete (RC) columns has become increasingly popular in recent years, resulting in very promising results. Existing research, primarily focused on columns fully wrapped with FRP jackets, has demonstrated that FRP strengthening considerably affects both their strength and ductility. However, the current focus has transitioned towards partial confinement, which is more cost-effective as it requires less FRP and adhesive, and is also simple and quick to implement on-site. Using the finite element program ATENA GID 3D, a 3D finite element model of a CFRP partially confined square reinforced concrete column subjected to eccentric loading has been created for this investigation. The numerical models were validated through comparison with the results from a subsequent experimental study. To investigate the effects of confinement configurations, slenderness ratio, strengthening ratio, concrete strength, and load eccentricity on column behavior, parametric research was conducted. The results indicated that an increase in load eccentricity leads to a considerable decrease in the load-bearing capacity of columns, while the mid-height horizontal displacements remain unaffected by eccentricity. The effectiveness of partial confinement decreases as the concrete grade rises. An increase in the slenderness ratio results in a significant reduction in their ultimate load-bearing capacity, accompanied by an enhancement in the lateral ductility of the columns. Concerning the strengthening ratio, an optimal value is found between 3 and 5 confining layers, which helps to minimize material waste and reduce costs. The best performance regarding ultimate load and lateral ductility ratio is attained by both configurations featuring small distributed wraps and a single large central wrap, which also necessitate the least amount of labor cost.