Application of output-only modal method in monitoring of bridges using an instrumented vehicle

In this paper, application of a well-known output-only modal analysis method called Frequency Domain Decomposition (FDD) method in monitoring of bridge frequency is presented. The obtained modal data can be used efficiently for bridge health monitoring. Three measurement strategies are suggested to collect the acceleration responses from vehicle axle for FDD method in a numerical study. It is shown that using multi vehicles leads to better results in compare to using one vehicle. The efficient effect of ambient excitation to all sides of the bridge is also discussed. In addition, application of FDD method in the case of closeness of vehicle frequency to bridge frequency is investigated. Finally, it is discussed that the FDD method can be an efficient alternative to FFT analysis which is common for analysing the vehicle measurement passing over the bridge.