Experimental and numerical study on the effect due to passengers on flexural vibrations in railway vehicle carbodies

The effects of passengers on vertical flexural vibrations of railway vehicle carbodies have been investigated experimentally and numerically. The primary focus is the damping effect caused by passengers. Vibration measurement tests, including stationary excitation tests and a running test on a commercial line, were conducted on three different types of actual railway vehicles for varying the numbers, postures and distributions of passengers. The measurement results showed that the peak frequencies in the measured FRF (frequency response function) and acceleration PSD (power spectral density) in response to excitation force or acceleration changed only a little; in contrast large reduction of the peak values was observed when passengers were aboard. These results show that passengers behave not as additional mass but as damping elements upon the carbody flexural vibrations. The damping effect by passengers appeared over several flexural modes and was significantly induced even by few passengers. Numerical studies were also carried out to develop analytical models for representing the measured results of the vibrations of carbody with passengers. It was shown that the change of the carbody FRF due to passengers could be simulated well by using a simple one-degree-of-freedom passenger model comprising a mass–spring–dashpot with a large damping ratio.