Abstract:Based on the theory of the equivalent stress range, almost half a year traffic data of two bridges were adopted to assess the fatigue behavior of the butt weld of the close rib. Due to the length of the stress influence line of the butt weld was relatively short, the axle loads were used to pass the influence line instead of the vehicle loads. The equivalent stress range was obtained and then compared with the result of the method in China specification. It showed that the equivalent stress range obtained from the practice axle loads is less than the value in China specification, at last the values of damage equivalent factors are discussed.