Dynamic Coupling Effects and Frequency Shifts in Vehicle-Bridge Interaction Systems for Indirect Bridge Monitoring

This study presents an integrated theoretical and experimental framework for characterising frequency shifts induced by dynamic coupling between a moving vehicle and a bridge using the vehicle-scanning method (VSM). Both analytical modeling and laboratory testing are used to demonstrate how vehicle–bridge interaction (VBI) affects the apparent frequencies identified from the responses of the vehicle. The analysis shows that VBI introduces frequencies that are different from the natural frequencies of the vehicle and bridge systems individually. Using a heavier test vehicle tends to result in an underestimation of the bridge frequency and an overestimation of the vehicle frequency. Furthermore, the rolling frequency effect is observed experimentally in the vehicle spectrum for the first time, marking a new contribution to our understanding of vehicle-induced dynamic behaviour. This combined theoretical and experimental approach provides comprehensive insight into the mechanisms governing coupled frequencies, supporting the development of indirect bridge health monitoring based on vehicle dynamics.