Fatigue damage evaluation of steel bridges considering thermal effect

With the change of external environmental factors, thermal loads are changing and causing fluctuating thermal stresses in critical fatigue details of steel bridges, which contribute to fatigue damage cumulation significantly. This paper proposed two fatigue evaluation methods considering the coupling effects of traffic load and thermal load: (1) Evaluation based on vehicular fatigue load model (VFLM) and thermal fatigue load model (TFLM). (2) Evaluation based on measurements of thermal load and traffic load. The analytical approach for obtaining the thermal fatigue load model was introduced, and the concept of the coupling stress model of 'wave-surfer model' was set up according to the mechanism of fatigue damage cumulation. Taking a steel box girder bridge as a case study, the collections of temperature data and traffic information were carried out. The two evaluation methods based on different load information were applied to two typical fatigue details, and the corresponding fatigue damage was calculated, which demonstrates that thermal effects should be taken into account for fatigue evaluation.