A Noncontact Methodology for Disengagement Monitoring of High‐Speed Railway Bridge Bearings Based on Bearing‐to‐Beam Displacement Relation Under Round‐Trip Trains

Bearings are critical components of bridges and are susceptible to various forms of deterioration under the action of traffic loads and complex environmental conditions. Existing methods for assessing the condition of bearings, including visual inspections, force sensors, cameras, and vibration sensors, still present challenges in accurately locating and quantifying disengagement. This paper proposes a novel data‐driven damage index based on the bearing‐to‐beam displacement relation under round‐trip trains for disengagement monitoring of high‐speed railway (HSR) bridge bearings and provides a rapid and efficient evaluation scheme using a noncontact visual measurement system. The dynamic responses of a spatial elastically supported beam subjected to moving loads are first derived, and a mathematical expression has been theoretically established to describe the relation between the damage index and the bearing stiffness. A numerical three‐dimensional (3D) train–bridge interaction (TBI) model is developed to validate the efficacy of the suggested approach. Finally, the feasibility of integrating noncontact visual measurement schemes in the disengagement monitoring of HSR bridge bearings has been successfully validated by conducting an on‐site experiment on the Yangcun Bridge. The research findings indicate that the proposed damage index exhibits remarkable insensitivity to noise under the random traffic flow, showing good damage localization and anti‐interference capabilities. The established mathematical expression accurately reflects the relation between the damage index and the bearing stiffness, and it can be considered in an actual test that bearing disengagement has occurred when the proposed damage index is larger than 0.5. The proposed methodology offers a rapid, accurate, and noncontact approach for the disengagement monitoring of HSR bridge bearings, contributing to the long‐term operational safety of bridges.