This paper is concerned with an improved Vehicle Scanning Method (VSM) for modal properties identification of bridges with allowances for damping and road roughness. Owing to the bridge damping, signals are small and degrade over time and may be corrupted by the road roughness. In order to enhance VSM in reading these weak signals, an appropriately tuned elliptic filter is employed instead of the conventional bandpass filter, such as the Butterworth filter. The VSM is improved further by adopting the recently developed Moving Internal Node Element (MINE) method that can furnish more accurate predictions of the higher natural frequencies of the bridge. Illustrative example problems involving undamped and damped bridges with or without road roughness are presented to show the superiority of the improved VSM over conventional VSM that uses a standard bandpass filter and finite element method for analysis. It will be shown herein that the improved VSM can identify the higher mode shapes even with a bridge damping ratio of 3 and standard road roughness, whereas the existing VSM could not do so.
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