Experimentally and Analytically Investigating Effect of Confinement on Behavior of RC Beams Reinforced by GFRP

Glass Fiber Reinforced Polymer (GFRP) rebars have high tensile strength and high resistance against corrosion. This study addressed the investigation of the confining effects of the transverse steel rebars on concrete beams reinforced using GFRP rebars. For this purpose, six beam specimens with cross-section dimensions of 20 and 30 cm and a span length of 200 cm were constructed. The rebars had cross-section area values of 1.7, 2.6, and 3.5 times the balance value. The middle of three beams was reinforced using stirrups with small spacing. These specimens were called confined beams. The specimens were tested under four-point static loading. The behavior of the unconfined and confined specimens was evaluated using the parameters of the initial yield strength, the stiffness of the cracking part, the ultimate load, and the ductility index. The experimental results indicate that confining the beams by steel stirrups increased the first three behavioral parameters to about 35, 27, and 29 percent, respectively. The ductility index for the two samples, having the longitudinal rebars of 2.6 and 3.5 times the balanced amount, decreased by about 6 and 22 percent. The other sample's ductility index increased approximately 6 percent compared to the control samples. Moreover, the capacities of both unconfined and confined specimens are estimated by existing analytical relationships with an error of 5 to 16 percent, having good agreements with the experimental results..