Experimental study on fatigue behavior of RC beams strengthened with carbon fiber laminates under cyclic bending loads

Fiber reinforced polymer (FRP) has been widely used to strengthen concrete structures in civil engineering recently. However there were few studies on the durability and fatigue behavior of reinforced concrete (RC) structures strengthened with FRP. In this paper, fatigue tests under cyclic bending loads at different temperature of 20 degrees C and 80 degrees C were carried out to investigate the fatigue behavior of the beams strengthened with carbon fiber laminates (CFLs). The test results show the failure modes of the strengthened beams under cyclic bending loads include concrete crush, CFLs debonded and steel bar broken. S-N curves of strengthened beams were developed according to the test results. The fatigue limit and Load-mid-span deflection curves of strengthened beams were obtained as well. The fatigue lives of the strengthened beams are not significantly influenced by the ambient temperatures when the peak loads equal 25.0kN, 27.5kN or 30.0kN. However, when the peak load equals 32.5kN, the fatigue lives decreased significantly with the temperature.