Fatigue behavior of concrete beams reinforced with glass- and carbon-fiber reinforced polymer (GFRP/CFRP) bars after exposure to elevated temperatures

This paper deals with fatigue performance of concrete beams reinforced with fiber reinforced polymer (FRP) bars after exposure to elevated temperatures. A total of 13 concrete beams reinforced with glass- and carbon-fiber reinforced polymer (GFRP/CFRP) bars were tested under static and fatigue loading after exposure to different levels of elevated temperatures. The influences of elevated temperature, holding time, fatigue load level and FRP bar type on the fatigue behavior of beams were investigated. The results showed that the elevated temperature exposure reduced more severely the fatigue life of GFRP-reinforced concrete beam than that of CFRP-reinforced beam below 400 °C, and GFRP- and CFRP-reinforced beams both lost their bearing capacities when the exposure temperature reached 600 °C. The elevated temperature accelerated the development of concrete strain, crack width and deflection of FRP-reinforced concrete beams with the number of fatigue cycles. The mid-span deflection was predicted using some existing models, and the CEB-FIP model showed the best accuracy with the coefficient of variation of 2.8–7.0%. The fatigue strength of GFRP- or CFRP-reinforced concrete beams is not affected by elevated temperatures up to 400 °C for 2 h.