Behavior of CFRP-Prestressed Concrete Beams under High-Cycle Fatigue at Low Temperature

This paper investigates the behavior of concrete beams prestressed with carbon fiber-reinforced polymer (CFRP) rods under high-cycle fatigue at low temperature. Seven precast T-beams were tested, including five beams prestressed to various levels with the CFRP rods and two beams with conventional steel strands. All beams had a history of sustained loading. Some beams were directly loaded monotonically to failure as control specimens. Other beams were subjected to three million cycles of flexural loading, either at room temperature or at -28°C, prior to being monotonically loaded to failure at the same temperature. All CFRP-prestressed beams survived the three million cycles, whereas the steel-prestressed beam did not. It was shown, however, that the bond between CFRP rods and concrete could be weakened because of cyclic loading, low temperature during loading, or high prestress level. This resulted in a premature bond failure at 70 to 90% of the full flexural strength in subsequent monotonic loading. Also, stiffness and camber gradually decreased during cyclic loading.