Refining the modal properties of damped bridges scanned by a single-axle test vehicle with field proof

A novel method is proposed to simultaneously identify the mode shapes and damping ratios of a damped bridge using a single-axle scanning vehicle. This paper starts with the theoretical formulation for the vehicle-bridge system. Then the zero-phase filtering technique is adopted to extract the component response that is free of the edge effect from the test vehicle's response. To remove the shifting and shrinking effects caused by bridge damping on mode shapes, a novel threestep mode shape correction method (MSCM) is newly proposed, which does not require prior knowledge of the bridge damping. In addition, a trial-and-error approach is newly proposed for objectively calculating the bridge damping ratio. The feasibility of the proposed method is verified by theoretical studies and field proof. New findings of the paper include: (a) all the mode shapes produced by the MSCM do not show any shifting or shrinking phenomena as previously encountered, (b) the proposed method can accurately determine the first few modal properties of damped bridges with damping ratio up to 5%, and (c) the modal properties identified by the proposed method are validated by results from theory and field measurement for a three-span continuous bridge.

Automated summary

A novel method is proposed to simultaneously identify the mode shapes and damping ratios of a damped bridge using a single-axle scanning vehicle. The paper introduces a new three-step mode shape correction method that does not require prior knowledge of the bridge damping. The feasibility of the proposed method is verified through theoretical studies and field proof, showing accurate determination of modal properties of damped bridges.