Vehicle Scanning Method for Bridges

7Filtering Technique for Eliminating the Effect of Road Roughness

By letting a test vehicle move over a bridge, one can identify the frequencies of the bridge by picking the peaks in the Fourier response spectra of the test vehicle. One problem with this approach is that the vehicle frequency (undesired) may appear as a dominant peak in the spectrum, making it difficult to identify the bridge frequencies (desired). To enhance the visibility of bridge frequencies, an effective filter is needed to filter out the vehicle frequency. As a preliminary attempt in this study, three filters are adopted, the band‐pass filter (BPF), singular spectrum analysis (SSA), and the singular spectrum analysis with band‐pass filter (SSA‐BPF) proposed by Yang et al. (2013a) as a combination of the above two. Through numerical study on two cases with the vehicle frequency smaller or larger than the first bridge frequency, the SSA‐BPF technique has been shown to be most effective for extracting the bridge frequencies, due to its salient feature that there is no need to select the number of singular values, as required by SSA, while the unexpected peaks encountered by the BPF are avoided. The materials presented in this chapter are based primarily on Yang et al. (2013a).

7.1 Introduction

By letting a properly instrumented test vehicle travel over a bridge, one may extract the vibration frequencies of the supporting bridge from the dynamic response recorded for the test vehicle during its passage ...