Fatigue Life Prediction of Welded Joints in Orthotropic Steel Decks Considering Temperature Effect and Increasing Traffic Flow

Assessment is made for welded joints in orthotropic steel decks based on monitored field data from the Runyang Bridge by making use of the Palmgren–Miner rule and S–N curves. In contrast to previous strategies, interactive behavior of fatigue damage, ambient temperature, and traffic flow are considered. The results indicate that for long-span suspension bridge that is sensitive to temperature changes, fatigue damage accumulation is influenced by the ambient temperature in addition to the traffic growth. According to the fatigue equivalent index and statistical processing of traffic flow, the contribution of traffic growth to fatigue damage can be determined and then it is excluded from the total damage, so that the influence of temperature on fatigue damage is obtained. It is found that the ambient temperature has a linear effect on the fatigue damage of welded decks on the Runyang Suspension Bridge (RSB). Explanations for this temperature effect are given, and fatigue analysis of the Runyang Cable-stayed Bridge (RCB) is also made for comparison, consequently it is found that the proposed method in this paper might be applied to both suspension bridges and cable-stayed bridges. Finally, considering the influence of temperature and increasing traffic flow, the fatigue life prediction has been conducted.