Exploring GFRP bars as reinforcement for rectangular and L-shaped beams subjected to significant torsion: An experimental study

Steel corrosion related problems have been a heavy burden on countries economically and socially for many decades. Therefore, the inevitable quest to find an alternative for steel reinforcements is long overdue. On the other hand, fiber reinforced polymer (FRP) bars have non-corrosive nature and could be the solution for this problem. In this study, the objective is exploring the usage of glass fiber polymer (GFRP) bars as torsion reinforcement for L-shaped beams. New adhesively bonded GFRP stirrups are presented and implemented. Five beams were constructed and tested under significant torsion. The bonded GFRP stirrups were more effective as transversal reinforcement compared with the bent steel stirrups and the bent GFRP stirrups. It improved the ultimate torsional strength and increased the corresponding unit angle of twist and the maximum stirrup strain as well as the major concrete crack width. In addition, the increase in the GFRP transversal reinforcement percentage improved the ultimate torsional strength, the toughness, and the deformability. Moreover, the usage of a stirrup strain value of 0.4% resulted in overly conservative predictions for the ultimate torsional resistance; however, it provided adequate torsional deformability index and toughness.