Vehicle Scanning Method for Bridges

10Contact‐Point Response for Modal Identification of Bridges

The response of the contact point of the vehicle with the bridge, rather than the vehicle body itself, is a better parameter for modal identification of the bridge. In this chapter, approximate closed‐form solutions were first derived for the vehicle and contact‐point responses, and then verified by finite element solutions. The contact‐point acceleration is born to be free of the vehicle frequency, an annoying effect that may overshadow the bridge frequencies in the presence of surface roughness. From the frequency response function (FRF) of the vehicle with respect to the contact point, it was shown that the contact‐point response generally outperforms the vehicle response in retrieving the bridge frequencies in that it allows higher frequencies to be identified. In the numerical simulations, the contact‐point response was compared with the vehicle response for various scenarios. It is concluded that in each case, say, for varying vehicle speeds or frequencies, for smooth or rough road surfaces, with or without existing traffic, the contact‐point response outperforms the vehicle response in retrieving either the frequencies or mode shapes of the bridge. The materials presented in this chapter are based primarily on the paper by Yang et al. (2018a).

10.1 Introduction

The modal parameters of a bridge, including the frequency, mode shape, and damping, are the most useful information for engineering applications. ...