Fatigue experiments of eight I-steel beams strengthened with different fiber reinforced polymer (FRP) plates are presented in this paper. The experimental results show that, (1) under the principle of equivalent axial tensile stiffness of different types of FRP plates, the fatigue life of strengthened steel beam could increased by 3.33-5.26 times over un-strengthened steel beam, while the fatigue life of steel beam strengthened with welding steel plate increased by 1.74 times; (2) Application of FRP plates can significantly reduce the crack growth rate, prolong the fatigue life and even change the fatigue failure mode of I-steel beams compared with welding steel plates; (3) The CFRP plate with high modulus was found to be the most efficient strengthening way; (4) It was also observed that the interfaces treating method and the plate configuration have considerable influence on the fatigue life.
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