ABSTRACT
The natural frequency of bridges is one of the most key dynamic parameters that represents the characteristics of the bridge and is most useful for many purposes. The identification of the frequency of bridges is a problem widely encountered in bridge engineering. Recently, authors have shifted to extract bridges' frequency, “indirectly”, from the responses of a passing vehicle, which has become known as “drive-by” inspection. “Drive-by” Bridge inspection approach has been developed dramatically since it has the advantage of convenience, economy and safety. Previous studies have pointed out that the higher vehicle velocity amplifies the power for the bridge response in spectrum of Fast Fourier Transform (FFT), which consequently implies easier extraction for the bridge frequency from the vehicle responses. However, as the speed increases, the vehicle spends lesser time on the bridge and consequently the frequency resolution drops dramatically which result in a substantial error in the estimated frequency. This paper introduce a new frequency extraction technique based on Hilbert Transform (HT), which is not restricted to frequency resolution so as to improve recognition of bridge frequency. In this paper, a closed-form solution for the bridge frequency is derived from the vehicle response, taking into account removing the effect of the vehicle velocity. Then numerical Vehicle-Bridge Interaction (VBI) model with a quarter car model is adopted to demonstrate the proposed approach.
