An effective procedure for extracting the first few bridge frequencies from a test vehicle

This study presents an effective procedure for extracting the first few bridge frequencies using the data collected by a moving test vehicle. Previously, the effectiveness of the vehicle scanning method for bridge frequencies was hampered by factors such as vehicle frequency and road surface roughness. To this end, the contact-point response of the vehicle with the bridge that is free of the vehicle frequency is adopted in the analysis. To enhance the visibility of the first few bridge frequencies for extraction, the variational mode decomposition with band-pass filter (VMD-BPF) is proposed herein. The VMD is neater and more elegant than the empirical mode decomposition (EMD) in that less decompositions are needed, while there exists no mode-coupling problem, and the BPF serves to remove the undesired roughness frequencies. To verify the feasibility of the proposed procedure, both the vehicle and contact-point responses generated either numerically or by the field test are analyzed. It is demonstrated that the VMD-BPF is an effective method for extracting the bridge frequencies using the contact-point response for the scenarios considered.