Novel Shear Reinforcement for Fiber-Reinforced Polymer-Reinforced and Prestressed Concrete

Abstract

This article presents the findings of research conducted into the shear behavior of fiber-reinforced polymer (FRP)-reinforced and FRP-prestressed concrete beams containing continuous FRP helical transverse reinforcement. The authors contend that for FRP materials to proliferate as internal reinforcement and prestressing tendons for concrete structures, they should be used rationally, lest the indisputable advantages that these materials possess be lost due to poor design. The article reports on 12 tests that were conducted on ordinary reinforced beams and 15 that were conducted on FRP-prestressed concrete beams. The results showed that full-depth unbonded rectangular helixes were more effective than unbonded circular helixes for equal quantities of material. When used to resist shear, fully unbonded circular and rectangular helixes had to be spaced at a closer pitch in comparison with fully bonded or intermittently bonded rectangular helixes, to provide a similar increase in failure capacity. In addition, prestress aids FRP-reinforced concrete beams to a greater extent in increasing shear capacity than it does in the case of the equivalent steel-reinforced situation. The authors conclude by presenting comparisons between experimental results and existing design guideline predictions, demonstrating the conservative nature of the ACI-440.1R-03 shear clause.