Frequency extraction for bridges with rough surface by a moving test vehicle enhanced by a shaker

The response of a test vehicle moving over bridges may be worsened by vehicle's self frequency and pavement roughness, since they both can pollute the vehicle spectrum for bridge frequency identification. This paper is aimed at tackling the above two factors using a novel software/hardware means, i.e., by using the vehicle-bridge contact response to eliminate vehicle's self frequency, and a shaker to enhance the bridge vibration while reducing the pavement roughness. Firstly, new closed-form solutions are derived of the vehicle-shaker-bridge system to form the theoretical framework for future application of the shaker. Then, the contact response is back calculated from the equilibrium condition of the damped vehicle. Further, the simple formula newly derived for the shaker's dynamic amplification factor (DAF) on the vehicle and contact responses can be easily used. Based on the parametric study for the related factors, it is concluded that: (1) the shaker facilitates the vehicle scanning of frequencies for rough bridges, including the higher modes; (2) the shaker (i.e., frequency and location) can be tuned up using the DAF formula to meet the needs of various bridges; and (3) the combined use of the contact response and shaker is effective for general application.