Indirect Approach for Measuring the Bridge Frequencies in Consideration of the Road Surface Roughness and Nonlinear Vehicle Stiffness
Date Issued
2010
Date
2010
Author(s)
Wu, Fong-Bin
Abstract
The objective of this study is to investigate the feasibility of extracting the bridge frequencies from the dynamic responses recorded for a vehicle during its passage over the bridge, in consideration of the road surface roughness and nonlinear vehicle stiffness, and to examine if the response components corresponding to the bridge frequencies can be decomposed from vehicle acceleration responses by Ensemble Empirical Mode Decomposition (EEMD). The approach for extracting the bridge frequencies from the dynamic responses of a vehicle is referred to as indirect approach for measuring the bridge frequencies.
This study is theoretically based on the analytical solutions to the vehicle-bridge interactive problem derived by Yang and Lin (2005), which verifies that the bridge frequencies dominate the dynamic responses of the vehicle. But the analytical solutions are solved under ideal assumptions, not necessarily being applicable to more complicated cases. For more complicated cases such as those with the considerations mentioned above, they are solved by numerical simulations herein, in which the bridge is modeled as a Bernoulli-Euler beam and the vehicle as a moving sprung mass. The dynamic responses of both the bridge and vehicle, in consideration of the road surface roughness and nonlinear vehicle stiffness, are solved by a finite element procedure programmed by the author, in which the governing equations of the vehicle-bridge interactive system are assembled by those of the conventional bridge elements and vehicle-bridge interaction element and are solved by Newmark-β method. Then, performing Fast Fourier Transform (FFT) to the dynamic responses of the vehicle, the bridge frequencies are extracted from the corresponding Fourier spectra.
It is observed from the simulation results that the road surface roughness may cause negative consequences on the indirect approach for measuring the bridge frequencies, but such negative consequences could be decreased by introducing multiple vehicles other than the test vehicle and by raising the speed of the accompanying vehicles, and that the bridge frequencies are still extractable from the dynamic responses of the vehicle once the range of the varying vehicle frequency caused by the nonlinear vehicle stiffness does not cover the bridge frequency, and that the response components corresponding to the bridge frequencies can be decomposed from vehicle acceleration responses by EEMD.
Subjects
Vehicle-Bridge Interaction(VBI)
the bridge frequencies
acceleration
roughness
nonlinear
Ensemble Empirical Mode Decomposition(EEMD)
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