Tension–Tension Fatigue Behavior of Ribbed Glass Fiber–Reinforced Polymer Bars in Air

Fatigue resistance is a crucial aspect in the design of structural components subjected to cyclic loading. Due to the corrosion of steel reinforcement, glass fiber–reinforced polymer bars are increasingly being used in reinforced concrete members. However, very limited research has been conducted on the fatigue behavior of glass fiber–reinforced polymer reinforcement. This study builds upon previous fatigue test research performed at 4 Hz but also investigates low-frequency testing. Three adhesives were investigated to identify the optimal gripping system capable of withstanding fatigue loading. Nonshrink grout was determined to be the only suitable adhesive for avoiding unwanted failure modes. This study investigated stress levels ranging from 30% to 65% of the ultimate tensile strength depending on the frequency used. Tests at both frequencies yielded results within the expected S‒N curve, as in prior studies. Moreover, the equations of Sendeckyj showed good reliability of the data. Although North American codes limit fatigue cycle frequencies to between 1 and 15 Hz, this study found that the much lower-investigated frequencies of 0.03–0.04 Hz yielded excellent results within the expected behavior envelope. Low-frequency laboratory tests are advantageous to adopt because standard universal testing machines can be used, without the need for dynamic actuators.