Influence of Longitudinal GFRP Reinforcement Ratio on Shear Capacity of Concrete Beams without Stirrups

Fiber reinforced polymer (FRP) bars due to their excellent corrosion resistance, high tensile strength, good non-magnetic properties have been proposed for reinforcing concrete structures instead of traditional steel. Many research use glass fiber reinforcement as it is much cheaper than carbon one. The aim of this paper is to analyze the influence of longitudinal GFRP reinforcement on shear capacity of concrete beams without stirrups and to investigate a dowel effect of this reinforcement on the shear strength. The paper presents experimental test results of T- shaped, single span, simply supported beams without stirrups reinforced with longitudinal GFRP bars. The following parameters were investigated in the research: flexural reinforcement ratio, number of reinforcement layers, number and diameter of bars in one layer. Test results indicated no significant influence of the longitudinal reinforcement ratio on the shear strength in the beams with one reinforcement layer. However, in the beams with two layers of longitudinal reinforcement the significant increase in the shear strength was observed with increase in the reinforcement ratio (in a range from 1,02% to 1.85%). The beams reinforced with two layers of GFRP reinforcement showed more extensive crack pattern than the beams with one reinforcement layer. It confirms that application of two reinforcement layers more effectively enhance the shear strength mainly due to higher tension stiffening effect provided by the flexural reinforcement in the beams with two reinforcement layers.