Use of a passing vehicle to scan the fundamental bridge frequencies: An experimental verification

A two-wheel cart towed by a light truck is used to scan the fundamental frequency of vibration of a sustaining bridge. The truck excites the bridge through its movement, thereby serving as an exciter to the bridge. The bridge vibration is received or scanned by an accelerometer installed in the cart. The bridge that is set into motion will affect the dynamic response of the towed cart, which in turn serves as a receiver or scanner of the bridge's dynamic properties, especially the frequencies of vibration. The response recorded using an accelerometer installed in the cart is processed by a fast Fourier transform (FFT) to extract the “source” frequencies of the cart, which are exactly the frequencies of vibration of the bridge. The feasibility of scanning the fundamental frequency of the bridge using the towed cart is confirmed by field tests. The methodology developed for the first time herein is simple and efficient, and can be applied to a wide range of bridge problems, if only the fundamental frequency is of interest.