Extracting Bridge Frequencies from The Dynamic Responses of Moving and Non-moving Vehicles

Abstract

Bridges can continuously suffer from structural deterioration due to inclement environmental and operational effects, making a timely inspection necessary to ensure the reliability and functionality of bridges. Recent progress in vehicle-bridge interactions has promoted the vehicle scanning method (VSM) for bridge frequency extraction, whereby the bridge frequency is typically identified from the dynamic response of a passing vehicle to reflect the bridge's health condition. Despite numerous endeavors, the low-speed limitation of the moving test vehicle and the adverse influence of road roughness still hinder the general application of VSM. In this regard, this paper presents a novel VSM for bridge frequency extraction by integrating moving and non-moving vehicles. By introducing the novel non-moving vehicle, the bridge vibration content becomes more obvious in the dynamic response of the moving vehicle, which is beneficial to the associated indirect bridge frequency extraction. Moreover, the non-moving vehicle is nearly free from the influence of road roughness, such that the performance of VSM for bridge frequency extraction can be enhanced against noisy real-world environments. To understand the inherent mechanism of the proposed method, a vehicle-bridge coupling system with moving and non-moving vehicles is theoretically formulated, and the analytical solutions of the coupled system are derived and numerically validated. Furthermore, several case studies are presented to comprehensively investigate key factors affecting the performance of bridge frequency extraction through the proposed method. The results indicate that incorporating a non-moving vehicle can significantly increase the extractability of bridge frequencies in vehicle responses. It becomes possible to accurately identify the first four-order bridge frequencies of a simply supported bridge (rather than the first two-order bridge frequencies using a moving vehicle exclusively) from the vehicle response after introducing a non-moving vehicle. More importantly, the adverse effect of the high-speed moving test vehicle and road roughness can be significantly alleviated by the non-moving vehicle, and therefore the proposed method becomes more robust in actual applications. Besides, further insights are provided in terms of the implementation strategies of the proposed method.