Multi-task multi-level alarm of long-span railway bridge monitoring systems via excitation-response indicators cross-cooperation

There are multiple types of risks involved in the service of long-span railway bridges. Classical methods are difficult to provide targeted alarm information according to different situations of load anomalies and structural anomalies. To accurately alarm different risks of long-span railway bridges by structural health monitoring systems, this paper proposes a cross-cooperative alarm method using principal and secondary indicators during high-wind periods. It provides the prior criterion for monitoring systems under special conditions, defining the principal and secondary indicators, alarm levels, and thresholds based on the relationship between dynamic equilibrium equations and multiple linear regression analysis. Analysis of one-year monitoring data from a long-span railway cable-stayed bridge shows that the 10-min average cross-bridge wind speed (excitation indicator) can be selected as the principal indicator, while lateral displacement (response indicator) can serve as the secondary indicator. The threshold levels of the secondary indicator prioritize the safety of bridge operation (mainly aiming at the safety of trains traversing bridges), with values significantly lower than structural safety thresholds. This approach enhances alarm timeliness and effectively distinguishes between load anomalies, structural anomalies, and equipment failures. Consequently, it improves alarm accuracy and provides timely decision support for bridge maintenance, train traversing, and emergency treatment.