Probability-Based Optimization Method for the Fatigue Maintenance Strategies of Steel Bridge Welded Components

A probability-based optimization method for the fatigue maintenance strategies of steel bridge welded components was presented with the combination of linear elastic fracture mechanics(LEFM),the structure reliability theory and whole life cycle cost analysis method.Classification maintenance strategy was adopted according to the fatigue crack sizes of steel bridge welded components.Maintenance cost was divided into inspection,repair and failure costs according to the whole life cycle cost method.Maintenance strategy optimization was carried through based on the inspection,repair and failure probabilities of components,with the minimum total maintenance cost for the component to satisfy the minimum allowable reliability as optimization objective.Optimization analysis was carried on the fatigue maintenance strategies for the transverse stiffener in the steel box girder of certain suspension bridge.Results show that inspection cost has the most significant influence on the optimal maintenance time.The optimal maintenance time will be delayed by the increase of inspection cost.The optimal maintenance time will be advanced by the increase of repair cost.Discount rate can change the value for total maintenance cost,but when the probability of failure is very small,the increase of failure cost has little effect on the optimal maintenance time.The proposed optimization method for maintenance strategies is simple,practical and maneuverable,which can be applied to similar steel structures for maintenance optimization.