Incorporating Wheel Axle Inclination Effects into a Vehicle–Bridge Interaction System for Vehicle Scanning Method

The vehicle scanning method has been developed as a drive-by technique for identifying bridge dynamic characteristics from the responses of a moving test vehicle. In practical applications, however, geometric imperfections of the test vehicle, such as wheel axle inclination, may introduce additional frequency components into the measured vehicle response and affect the interpretation of the scanning results. A theoretical formulation is developed to describe the wheel axle inclination effects on the vehicle–bridge interaction system. The parametric investigation shows that the axle inclination angle primarily affects the amplitude of the harmonic excitation, whereas the wheel radius and vehicle speed determine its corresponding frequency in the vehicle spectrum. The analysis further shows that the harmonic component associated with axle inclination can be distinguished from bridge-induced frequency components based on its dependence on vehicle wheel characteristics. These findings provide a theoretical explanation for harmonic components observed in experimentally recorded vehicle responses and indicate that such components may serve as an indicator of wheel axle inclination in the vehicle scanning method.