Performance assessment of railway multispan steel truss bridge bearing by thermal excitation

The performance of bridge expansion devices (e.g., bearings or expansion joints)is a major concern for the operation department. A mechanical analysis model can be used to accurately analyze the influence mechanism of major factors and evaluate the working performance of bridge expansion devices with structural health monitoring data. Considering the nonlinear characteristics of bearing friction, a friction hysteresis model was established in this study to analyze the behavior of the bearing longitudinal displacement (BLD) under thermal excitation. The friction hysteresis model can describe the motion path of the BLD under periodic temperature. The variation in the model parameter is defined as an evaluation index that can reflect the degradation in the working performance of the bearing. The periodic change in the temperature is the driving force for developing the friction hysteresis model, and the calculation of the temperature-induced BLD is critical in extracting the evaluation index. Therefore, a calculation formula for the BLD of the steel truss bearing was derived considering the temperature gradient. Finally, the application of this method was verified through the temperature and BLD monitoring data of a multispan continuous steel truss arch bridge. The results showed that the evaluation index variance can describe the maximum bearing friction increase. However, the proposed approach is primarily based on thermal excitation, because of which it cannot assess the bearing working performance if the uncertainty in the friction hysteresis model is introduced by other types of excitations (e.g., vehicle excitation).