Comparative research on low cycle fatigue performance of the GFRP(Steel)-RC beams

In harsh environments, there are more and more cases of using GFRP (Glass fiber reinforced polymer) bars instead of Steel bars to strengthen concrete structures. While the corrosion durability of the structure is greatly improved, the structural stiffness of the GFRP-reinforced concrete (GFRP-RC) structure will be significantly reduced. In order to compare and study the difference in structural stiffness under static and low-cycle fatigue tests, this paper tested 12 GFRP (Steel)-RC beams. The results show that under the ultimate static load, the mid-span deformation of the GFRP-RC beam is 2.3 times that of the Steel-RC beam. Under a high fatigue load (S = 0.85), the fatigue stiffness of GFRP-RC beams is 28.69 % lower than that of Steel-RC beams, but the cumulative value of fatigue damage is also decreased by 24.14 %; In addition, under a lower fatigue load (S = 0.70), the cumulative fatigue damage of GFRP-RC and Steel-RC beams increased by 4.07 % and 13.90 %, respectively, compared with S = 0.85, indicating that GFRP-RC beams better durability under the two types high fatigue stress. Based on the maximum fatigue deflection test parameters of GFRP (Steel)-RC beams, the dynamic stiffness degradation models and fatigue damage evolution models were established, and the accuracy of the fatigue damage evolution model was verified.