Analysis on Fatigue Damage of Long-span Bridges Considering Effect of Environment Varying-temperature
Based on temperature-history data recorded by structural health monitoring system (SHMS) installed on long-span bridge, the characteristics of the temperature in the top deck and bottom deck of the steel box girder was studied. According to the indirect coupling method, temperature was regarded as body load and applied to three-dimensional multi-scale finite element (FE) model. Structural stress induced by temperature can be obtained and the analysis from thermal to the structure was realized. And then, based on the strain data from SHMS, the difference of strain characteristics induced individually by vehicle loads and environment temperature were investigated. Strain histories caused by the above factors were separated and extracted, and they were compared with the results by the FE simulation. Finally, based on the continuum damage mechanics, the cumulative fatigue damage of the bridge was induced by vehicle load separately as well as the interaction of vehicle load and environment temperature. The results show that the analysis flow of fatigue damage proposed in this paper can realize fatigue damage analysis at key locations of bridge under the action of environmental temperature and vehicle load. Fatigue damage caused by the temperature alone is small and can be ignored. But the fatigue damage caused by the interaction of these two loads has significant difference with that caused by the vehicle alone. At the beginning of the service periods, the influence of temperature on damage is not significant, but with the increase of fatigue damage, the influence of the interaction of these two loads becomes more prominent. That indicates that loads induced by temperature change accelerate the rate of fatigue damage accumulation at the mid-late service periods, and have a significant impact on the structure fatigue life.
Keywords: long-span bridge, varying-temperature, fatigue damage, stress history effects, finite element analysis
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