Bridge frequency identification based on relative displacement of axle and contact point using tire pressure monitoring

The identification of bridge frequency (BF) using the responses of moving vehicles has received growing interest in recent years. In this study, a two-stage framework was developed to extract the BF using the tire pressure of a vehicle crossing it. The first step was to establish and calibrate a tire pressure model, which facilitates the interpretation of the relationship between the tire pressure change and relative displacement of the axle and contact point (RD of A-CP). To satisfy the field test requirements, a quarter-car model representing the rear axle system of a half-car model was adopted; thus, the excitation from the front suspension vibration could be neglec-ted. In the second stage, the calibrated tire pressure model was used to identify BFs, by combining it with field measurements of the rear tire pressure change of a traversing vehicle. The A-CP displacement estimation method was formulated using the estimated rear axle RD of the A-CP. In addition, a residual displacement method was proposed to eliminate the adverse effects of road roughness; this used the estimated CP displacement of the rear tire over two runs, and the BF could be identified from the residual response. From numerical simulations, we verified that the proposed CP displacement estimation and road roughness elimination methods were reliable, allowing the identification of BFs with satisfactory accuracy. Finally, the performance of the proposed two-stage framework was comprehensively determined in both laboratory experiments and field tests using a real inspection vehicle. The limitations of the present study and recom-mendations for future work were also addressed.