Mitigation of Effect of Bridge Modal Resonant Interference Induced by Road Roughness in the Vehicle Scanning Method

Road roughness is a constant disturbance in vehicle-bridge interaction and a challenge to practical application of the vehicle scanning method. Unlike previous studies, the effect of roughness is deepened in the analytical formulation of the vehicle-bridge interaction system in terms of the associated bridge modal response component and its transfer to the scanning vehicle. The results show that the roughness frequencies may satisfy a bridge modal resonance condition and generate a resonant response that overlaps the moving load response. This effect is referred to as bridge modal resonant interference, which affects the bridge related response used for mode shape and damping ratio identification in the vehicle scanning method. To quantify this effect, the roughness-load and roughness-initiation envelope ratios are established using the moving load and initial bridge responses as references, respectively. The former is essentially independent of the scanning vehicle mass, whereas the latter decreases with increasing initial bridge response and decreasing scanning vehicle mass. This contrast supports the excitation-acquisition separation, in which an initial bridge response is established prior to scanning and a light scanning vehicle is used for response acquisition. Finite element responses are then processed for modal projection and vehicle response reconstruction to verify the envelope ratio relationships. Parametric analyses show that road roughness level, vehicle natural frequency, vehicle damping, and bridge damping increase the relative influence of resonant interference, whereas vehicle speed has a nonmonotonic influence. These findings provide a theoretical basis for potentially improving the practical applicability of the vehicle scanning method under road roughness conditions.