Extraction of bridge frequencies from the dynamic response of a passing vehicle enhanced by the EMD technique

The indirect approach previously proposed for extracting the bridge frequencies from a passing vehicle works mainly for the first frequency. In order to extract bridge frequencies of higher modes, the vehicle response will first be processed by the empirical mode decomposition (EMD) to generate the intrinsic mode functions (IMFs), and then by the fast Fourier transform. One feature with the EMD technique is that frequencies of higher modes can be made more visible by the sifting process. To verify the feasibility of such an approach, the vehicle response generated by the finite element simulations will first be analyzed, with results compared with the analytical ones. Then the same procedure will be adopted to extract bridge frequencies from the recorded response of a passing vehicle, with results compared with those from an ambient vibration test. It was demonstrated that using the IMFs computed from the vehicle response, rather than based on the original data, bridge frequencies of higher modes can be successfully extracted. Future directions of research are highlighted.