FATIGUE DAMAGE ASSESSMENT of STEEL BRIDGES USING STRAIN MEASUREMENT
The methodology and strategy for evaluating fatigue damage and possible critical locations of local fatigue on bridge-deck sections are developed, using the real-time monitoring data and the fatigue damage model based on continuous damage mechanics. A local damage model for evaluating the fatigue damage of bridge-deck sections is proposed, which allows fatigue damage to be considered at the continuum scale as a deteriorating process with its physical mechanism such as fatigue crack initiation and growth. Therefore the fatigue damage variable associates not only cycles of stress range on the accumulated process of fatigue, but also relates directly to the state of deterioration and the mechanics behavior in supporting the net stress. The effective stress range for the variable-amplitude stress spectrum due to traffic load is used to evaluate the fatigue strength of the bridge-deck section at different locations of strain gauges, by which the possible location of critical fatigue failure can be primarily determined. The method has been successfully applied to the Fatigue Damage evaluation for a suspension bridge under Typhoons and Overload Effect.