Experimental verification of indirect bridge mode shape identification using transmissibility of a passing vehicle

The use of structural vibration is one of the bridge health monitoring approaches which is often costly, time-consuming. The response of a passing vehicle includes the bridge response so that it is used for extracting the bridge modal parameters. In this paper, the transmissibility measurement of a passing vehicle is employed in order to identify the bridge mode shape indirectly. As the sensor is embedded on the axle of the vehicle, recording the signal is fulfilled during the vehicle passage and there is no need to stop the vehicle. On the other hand, there is white noise assumption in most other techniques, but excitation characteristics are not considered in the proposed method which is another advantage. In the numerical simulation, the bridge is assumed to be Euler Bernoulli and the vehicle is modeled as a 4DOF system. Solving the vehicle-bridge interaction equations, the acceleration of all degrees of freedom are obtained. Afterwards, the mode shape is identified by applying the short time transmissibility measurement on the acceleration. Since the performance of the indirect methods in real cases is associated with many obstacles and challenges, a setup for experimental verification of the proposed method has been designed and constructed in a laboratory. Numerical simulations and experimental results indicate the capability of the proposed method for indirect identification of bridge mode shape.