Fiber composites as reinforcement gained a great acceptance in reinforcement different concrete elements. This is due to its high tensile strength and its performance in the concrete columns as longitudinal and transverse reinforcement stirrups. In this study Glass Fiber Reinforced Polymers (GFRP) with different diameters are applied. Four groups of concrete columns with fixed longitudinal reinforcement of 4 Φ 10 as main steel reinforcement and different transverse reinforcement in diameter and number (stirrups) were studied. First specimen was the control one reinforced with ordinary steel reinforcement the other specimens reinforced using GFRP stirrups different in diameter Φ 6, 8, 10 and the number of stirrups in meter. The transverse reinforcement effects the ultimate failure, local capacity, lateral deflection and ductility ratio.
The vertical displacement, cracking load and ultimate load of the tested columns were recorded and analyzed. The ultimate load increased. In first group, the ultimate load increased by 8.2%, 23.5% and 44.3% as the confinement numbers of GFRP stirrups increased from 575 kN to 622 kN to 710 kN to 830 kN. For second group, the ultimate load increased by 30.4%, 37.4% and 54.8% as the confinement numbers of GFRP stirrups increased from 575 kN to 750 kN to 790 kN to 890 kN. For third group, the ultimate load increased by 39.1%, 47.8% and 60% as the confinement numbers of GFRP stirrups increased from 575 kN to 800 kN to 850 kN to 920 kN. NLFEA analysis was carried out.