Torsion behaviour of RC beams strengthened by NSM GFRP and steel bars

Near-surface mounted (NSM) fiber-reinforced polymer (FRP) reinforcement is an innovative, serviceable, and beneficial technique for RC (reinforced concrete) structure enhancement. Previous studies have proven that the epoxy-resin bonded NSM FRP method effectively achieved shear and flexural strengthening. However, for torsion strengthening, only a few researchers have utilized the NSM approach, and no research has focused on using GFRP. bars and epoxy adhesives. In this study, the behavior of RC beams under combined torsion is investigated. when they have been enhanced with NSM GFRP and steel bars. Three RC beams with dimensions of (150×250×2000) mm (width x depth x length) were considered in the experimental tests. One RC beam is not strengthened and used as a control beam C.B., while the other two beams are strengthened with NSM GFRP bars and NSM steel bars. Test results in terms of twist angle-applied torque curves, the torque of initial cracks, ultimate torque capacity, and ultimate angle of twist were measured and analyzed. It has also been shown that the RC beam’ torsional performance can be substantially improved by using NSM GFRP stirrups by about 73% higher than NSM steel stirrups.