Abstract: To reduce the fatigue life prediction error of steel structure using traditional fatigue prediction algorithm, the interval-probability reliability analysis method was presented to deal the fatigue life prediction of steel structure with the consideration of variables uncertainty. The parameters of the linear accumulative damage model and the crack propagation model were distinguished as probabilistic variables and interval variables based on previous studies. The theoretical foundation was established by the consistency relationship between the interval reliability and the probability reliability model with lognormal distributed variables in theory. The solving process was combined with definition of interval reliability index and the probabilistic algorithm. The results of typical fatigue details of actual bridge show that, when the variable coefficient of the stress amplitude is in the range from 0.25 to 0.35, the results of the interval-probability analysis are more conservative than that of traditional probability method.

Key words: bridge engineering, statistical mechanics, Miner's rule, crack propagation criterions, hybrid reliability model, fatigue life