Probabilistic Modeling of Fatigue Damage in Orthotropic Steel Bridge Decks under Stochastic Traffic Loadings

Fatigue truck models with deterministic parameters were developed int a stochastic vehicle flow model. A response surface method was used to approximate the function between vehicle axle weight and equivalent fatigue stresses with few training data to solve the time-consuming problem of bridge finite element analysis under traffic flow loads. A probabilistic fatigue damage modeling method was presented and applied to the rib-to-deck details of steel box girder bridges. Finally, the fatigue damage model was applied to the reliability assessment of steel box girder bridges, and influences of traffic flow parameters on structural fatigue reliability were studied. Numerical results indicate that the higher occupancy rate of heavy vehicle flow in a slow lane than in a fast lane mainly explains the decrease in the fatigue reliability of corresponding rib-to-deck details. The increase in vehicle axle weight causes a rapid decrease in the fatigue reliability index of steel box girders. The fatigue reliability index of rib-to-deck detail in the slow lane decreases from 3.42 to 0.72 when the annual linear growth factor ranges from 0 to 1%. The stochastic fatigue vehicle flow model and the probabilistic model for fatigue damage exhibit considerable potential in the probability assessment of bridge fatigue damage.