Normal- and High-Strength Concrete Circular Elements Wrapped with FRP Composites

Reinforced concrete columns usually have a minimum amount of transverse steel reinforcement this transverse reinforcement can have non negligible effects on the response of columns retrofitted with fiber-reinforced polymers (FRP). This paper presents a test program that was designed to study the behavior of small- and large-scale normal- and high-strength concrete circular columns confined with transverse steel reinforcement, FRP, and both transverse steel reinforcement and FRP under concentric loading. The effect of the main variables—such as the unconfined concrete strength, the volumetric ratio, the type and the yield strength of the transverse steel reinforcement, the concrete cover, and the number of FRP layers—are studied in this research program. The test results show that the enhancement of the confined concrete strength and strain is more pronounced in specimens with normal-strength concrete. It is also shown that the rupture of the FRP in the specimens with higher volumetric transverse steel reinforcement ratios corresponds to larger axial compressive strength and strain and that the postpeak behavior of these specimens is more ductile.