Strengthening of RC columns under eccentric loads using NSM steel and GFRP bars

Abstract

The behavior of eccentrically loaded RC columns strengthened by NSM steel and glass fiber reinforced polymer (GFRP) rebars is investigated in this study. A total of six RC column specimens have been cast in this study with dimensions of (150×150×1200) mm (width × height × length). Two column specimens are unstrengthened and considered as controls, while the other specimens are strengthened by the NSM method using steel bars and hybrid steel and GFRP rebars. All column specimens have been tested under concentric and eccentric loads with an eccentricity of 75mm up to failure. Experimental results in terms of crack patterns, modes of failure, and load-displacement curves are all monitored, recorded, and assessed. The experimental results have shown an improvement in the ultimate load capacity for all strengthened column specimens. Further, results have demonstrated that, under concentric load, the almost similar enhancement in the strength of NSM-strengthened RC column specimens using steel bars only and hybrid steel and GFRP bars. However, at eccentric load, the ultimate load capacity of the strengthened RC column was increased by 62% and 79.45% compared to the control column using NSM steel and hybrid steel, and GFRP, respectively. Finally, this study found that at e/h = 0.5 using GFRP in the tension zone increased the ultimate load by about 11% when compared to steel.