Shear resistance of RC circular members with FRP discrete hoops versus spirals

Nowadays, design guidelines and codes contain valuable shear provisions for the design of concrete bridge members reinforced with fiber-reinforced-polymer (FRP) bars. Limited researches seem to have assessed the shear strength of circular concrete members reinforced with FRP reinforcement. Therefore, these standards do not provide specific formulae for circular RC members designed with FRP bars, hoops and spirals under shear loads. This paper reports experimental data about the shear strength of circular concrete specimens reinforced with FRP bars, discrete hoops and continuous spirals. Full-scale circular concrete specimens with a total length of 3,000 mm and 508 mm in diameter were constructed and tested up to failure. The test parameters included the type of reinforcement (glass FRP and carbon FRP versus steel) and configuration of the shear reinforcement (discrete hoops versus continuous spirals). The investigation revealed that the specimen reinforced with FRP hoops exhibited high load-carrying capacity comparable to the counterpart reinforced with FRP spirals. The experimental shear strengths of the FRP-reinforced concrete specimens were compared to theoretical predictions provided by current codes, design guidelines. The results of this study can be used as a fundamental step toward code provisions for using GFRP or CFRP spirals and hoops as internal shear reinforcement.