Early Warning for Abnormal Cable Forces of Cable-Stayed Bridges Considering Structural Temperature Changes

The deterioration or damage of stay cables can threaten the safety of bridges. It is difficult to judge whether a stay cable is deteriorated only by the variation in cable force because cable force also varies with temperature. Therefore, an early warning method for abnormal cable forces of cable-stayed bridges considering structural temperature changes is proposed in this paper. In the proposed method, a baseline model is established to characterize the normal relationship between the healthy cable force and structural temperatures, so the abnormal cable force can be detected by inspecting the residual between the identified cable force to be detected and the cable force predicted by the baseline model. First, the frequency–temperature relationship (FTR) model obeyed by a healthy cable is established by analyzing the mechanism of cable force change caused by structural temperature changes in bridge components from the perspective of deformation coordination. Then, the prediction error is inspected by constructing a mean value control chart of the modeling error generated from the baseline FTR model. An early warning will be triggered when the prediction error exceeds the control limits. Finally, the proposed method is applied to an actual cable-stayed bridge to verify its effectiveness. The results show that the modeling and prediction capabilities of the established FTR model are satisfactory and that the abnormal changes in cable forces can be detected by the proposed early warning method with satisfactory accuracy.