Numerical Simulation of the Behaviour of RC Columns Strengthened Using Hybrid NSM Steel and GFRP Bars

Abstract RC columns in concrete buildings frequently require strengthening, either as a result of problems in the columns themselves, having to sustain more loads than those expected during the initial design or as a result of aging or accidental damage. In recent years, the use of fiber-reinforced polymers (FRP) in strengthening existing RC columns has become more common, and the results are very promising. In this paper, a numerical study has been conducted on the behavior of eccentrically loaded RC columns strengthened with hybrid near surface mounted (NSM) steel and glass fiber-reinforced polymer (GFRP) bars. A numerical model is first proposed to simulate the behavior of hybrid NSM bars strengthened columns using the finite element program ABAQUS/Standard. The proposed model was validated against the experimental test published by the authors. Validation results have shown good agreement between the numerical and experimental outcomes in terms of load-displacement curves and failure modes. Further, a parametric study has been conducted to understand the effect of important parameters on the response of the hybrid NSM bars strengthened RC columns. Parametric study results have shown that the ultimate load of hybrid NSM bars strengthened RC columns increased up to 70% compared with that of columns strengthened with NSM steel bars only. Numerical results have also revealed that the ultimate load of the strengthened RC columns increased with increasing the number of NSM bars but decreased with increasing the slenderness ratio.