Dynamical Simulation of Rapid Transit Vehicles

A 28-degree–of-freedom dynamical model is established in the present study to simulate the responses of rapid transit vehicles. The model takes wheel conicity, creep force, track irregularity, etc. into consideration. Among them, the power spectral density function of track irregularity proposed by US Federal Railroad Administration (FRA) is considered the major input. Dynamical simulation of rapid transit vehicles under various suspensions, vehicle velocities, loads, wheelflats, and track irregularities are performed and compared. The investigation also covers situations when the vehicle is fully loaded of passengers and moves on either straight or curved tracks. Both Nadal ratio and wheel load reduction ratio are used to evaluate the possibility of vehicle derailment. Whether it is necessary to stop operation at the occurrence of an earthquake of intensity four as the regulation set by Taipei Rapid Transit Corporation is investigated as well. Through the study, it is found that, when the railway vehicle is fully loaded of passengers and runs at curved tracks, the lateral displacement of the wheelset is several-time greater than that of the empty train. The displacement increases as the curvature increases. The degree of track irregularity also affects the lateral displacement of the wheelset. In particular, the displacement caused by track irregularity of level one is several-time greater than that caused by track irregularities of other levels. It may exceed the limit value of 6 mm set by Taipei Rapid Transit Corporation when the vehicle is fully loaded of people. Finally, when an earthquake of intensity four occurs, although the phenomenon of wheel contact may occur, the calculated Nadal ratio and wheel load reduction ratio remain within their limit values. Therefore, it is still considered safe to passengers.