Detection of soil-abutment interaction by monitoring bridge response using vehicle excitation

This paper aims to explore fundamental characteristics of bridge vibration spectra to potentially evaluate soil-abutment interactions and changes in abutment earth pressures. To this aim, the bridge response to the excitation of an approaching vehicle on road is utilized to evaluate the transmissibility of the road-soil-abutment-bridge (r-s-a-b) path. By comparing the FFT spectrums of bridge acceleration responses before and upon a vehicle traversing over an abutment, we found that the response spectrum consists of specific frequency of vehicle excitation, even though the bridge response before vehicle traversed over the abutment has a much smaller magnitude. This suggests that the bridge response before the vehicle traversed over the abutment is sensitive enough to be used to characterize the dynamic features of r-s-a-b transmissibility. Hilbert–Huang Transform method is used to extract the non-stationary information of the moving vehicle excitation from the bridge responses to characterize the r-s-a-b transmissibility. It is found that specific signature associated with the specific frequency of vehicle excitation can be extracted from the Hilbert spectrum of empirical modal decomposition signals, and this signature could be readily quantified as a monitoring index which exhibits time-varying property.