從移動車輛反應擷取橋梁振動頻率(I)

The dynamic interaction between a moving
vehicle and the sustaining bridge is studied in
this project. By the method of modal
superposition, approximate but highly
accurate closed-form solutions are obtained
for the vertical responses of both the bridge
and moving vehicle, assuming the
vehicle/bridge mass ratio to be small. For
both the bridge and vehicle responses, it is
confirmed that rather accurate solutions can
be obtained by considering only the first
mode. The displacement, velocity, and
acceleration of the bridge are governed at
different extents by two frequency sets
pertaining to the driving frequency of the
vehicle and natural frequencies of the bridge.
From the spectrum for the bridge
displacement, the vehicle speeds can be
shown to be associated with some
low-frequency pikes. On the other hand, the
vehicle responses are governed by five
distinct frequencies that appear as driving
frequencies, vehicle frequency, and bridge
frequencies with shift. From the vehicle’s
acceleration spectrum, the first bridge
frequency (with shift) is shown to have rather
high visibility and can be easily identified.
Potential applications of the present results,
as well as further researches required, are
also indicated in the project.