Abstract: Based on the assumption of linear asymptotic superposition， the formulae for computing a stress intensity factor of an FRPreinforced bridge under threepoint bending were deduced theoretically. The fatigue crack propagation of the bridge was analyzed through experiments， and it was verified that the empirical formula for the crack mouth opening displacement (CMOD) can be used to calculate the CMOD of a beam under threepoint bending， by which the critical effective crack length of the bridge in a fracture model was calculated. Fatigue crack growth was quantitatively described via the stress intensity factor in linear elastic fracture mechanics， thus the fatigue life of an FRPreinforced bridge was forecasted.

Key words: fiber reinforced plastics (FRP), constant amplitude loading, crack growth, fatigue life, stress intensity factor (SIF)