Reinforced concrete columns strengthened with near-surface mounted and hybrid FRP under compression with or without eccentricity: Experimental study and finite element modeling

The utilization of FRP in strengthening of reinforced concrete (RC) columns has garnered significant attention in the past two decades. Researchers have proposed the use of near-surface mounted (NSM) FRP bars with (hybrid) or without FRP jackets alongside the conventional approach of column strengthening through jacketing particularly in the presence of load eccentricity. In the realm of static loading scenarios, a significant focus has been directed toward the evaluation of the NSM, jacketing, and hybrid methodologies, while comparatively less attention has been given to the impact of various parameters on the capacity. In this article, a total of 22 RC column specimens with medium slenderness were tested under axial compressive loads with or without eccentricity to study the effect of the parameters the number and type of NSM FRP bar, the number of layers and type of FRP jacket, and the groove size for FRP bar mounting. The experimental results reveal the beneficial effects of using FRP jackets, increasing their layers and groove dimensions, and augmenting the number of NSM FRP bars on column capacity and ductility up to 36% and 197% respectively. Additionally, an accurate Finite element model has been developed and role of corbel in eccentricity application is investigated. The results showed that the corbel is not capable of transmitting the desired eccentricity.