In recent years, bridge health monitoring systems have received widespread attention. By analyzing monitoring data, it is possible to assess the health status of bridges, improve inspection efficiency, and reduce maintenance costs, which is of great significance for ensuring the safety of train operations. This paper designs an FBG strain sensor with adjustable sensitivity based on the principle of FBG strain sensors, and combines it with a monitoring system to perform health diagnostics on bridge structures. From the perspectives of structural safety risks and environmental factors, seven bridge safety risk indicators are proposed. Building on the AHP hierarchical analysis method, the Decision Laboratory method is introduced, and a combined AHP-DEMATEL approach is used to quantitatively assess bridge risk conditions. Based on the average temperature changes measured by FBG sensors, the range is [-48.5, -42.91], and the average strain range is [2859.03, 4915.4]. Most of the tested bridges fall into the third-category risk level, with risk values between 4 and 5.5.
