Damping Effect Due to Passengers on Flexural Vibrations of Railway Vehicle Carbodies and a Simplified Modeling to Develop Vibration Reduction Devises Utilizing the Effect of Passengers

Passengers boarding on a railway vehicle are usually treated as additional mass in designing carbody and the natural frequencies of carbody flexural vibrations are considered to decrease as the number of passenger increases. However, some previous studies indicate that on-board passengers behave not as additional mass but as damping. This paper examines the damping effect due to passengers by using actual railway vehicles and compares the measurement results to the cases that iron blocks or water tanks are loaded. A stationary excitation test in the rolling stock testing plant for a commuter-type vehicle and a running test on a commercial line for a Shinkansen-train were conducted. From both tests, relatively large vibration reduction effects upon different natural modes of flexural vibration of the carbodies and little change of their natural frequencies were observed when passengers were aboard. On the other hand, natural frequencies were decreased when iron blocks or water tanks were loaded. The authors also tried to develop a numerical model to express the flexural vibration of carbody with passengers. It was found that a simple 1-DOF mass-spring-damper system with low natural frequency and high damping ratio can simulate a passenger well. According to those measurement results, it is expected that a new and valuable damping device against carbody flexural vibrations can be realized if we can simulate or mimic the effect of passengers correctly. Some basic directions or policies to develop such damping devices were discussed.