Experimental Study of Fatigue Flexural Performance of Concrete Beams Reinforced with Hybrid GFRP and Steel Bars

Concrete beams reinforced with a combination of steel and glass fiber-reinforced polymer (GFRP) bars exhibit promising strength, serviceability, and durability. The fatigue performance of concrete beams with hybrid reinforcement has not been studied previously. This paper designs an experimental program to investigate the fatigue flexural performance of concrete beams with longitudinal tension reinforcement of steel and GFRP bars. One static flexural specimen and three fatigue flexural specimens are tested. The influences of the fatigue load and reinforcement ratio on the fatigue behaviors are investigated. The fatigue loading level and the effective reinforcement ratio influence the fatigue life. The fatigue loading has little influence on the neutral axis depth. The curvature and midspan deflection increase significantly with the fatigue cycles before 0.01 million cycles and then increase slightly with the fatigue cycles after 0.01 million cycles. During the majority of the fatigue life, crack widths develop slowly. Different theoretical models for the midspan deflection of the concrete beams with hybrid reinforcement subjected to fatigue loading are developed and compared with the test results, and the selected model shows satisfactory accuracy. (c) 2017 American Society of Civil Engineers.