AN EVALUATION OF PASSENGER MASS EFFECTS IN CRASHWORTHINESS ANALYSES OF HEAVY RAIL VEHICLES

The ASME RT-2 Safety Standard for Structural Requirements for Heavy Rail Transit Vehicles requires that crashworthiness analyses be performed for two primary collision scenarios. Both scenarios use a moving train colliding into a stopped train in their ready-to-run loading condition where no passenger mass is included in the analysis. This standard is now frequently cited in technical specifications for new vehicles by transit agencies in North America. When evaluating a collision scenario, it is a logical extension to consider including passenger weights. A collision has a greater risk of injury if more passengers are onboard. In addition, additional passenger weight increases the kinetic energy at a specific collision speed, which can contribute to the collision severity. The difficulty of including the passenger load is that the passengers are loosely coupled to the train collision response and have independent collision behaviors based on the passenger configurations relative to the vehicle interior. The corresponding occupant decelerations can occur over different time frames than the vehicle deceleration. This paper describes a 1-dimensional lumped mass method for incorporating passenger weight into crashworthiness analysis. Each car in the train, the large car body mass is given the ready-to-run weight. The additional passenger load is divided into separate masses that are coupled to the car body using nonlinear springs. The separate passenger masses and attributes for the springs are derived from the specific seating layout of a car. Passengers are grouped by the various seating configurations with different timescales for coupling their mass into the car body. Several collision analyses were performed with this 1D model for the LACMTA HR4000 heavy rail vehicle at the speeds specified in ASME RT-2 (24 and 40 km/h) at both the ready-torun weight and at the maximum passenger weight. The influence on the crash dynamics and overall permanent stroke of the crash energy management (CEM) structures at each car interface is discussed. For the seating configuration used, a small fraction of the passenger mass is seen to influence the crash dynamics. This is because of the relatively long time it takes to couple much of the passenger mass into the car body relative to the short duration of the primary crash pulse on a car. Consequently, the addition of a large passenger weight did not require a commensurate increase in energy absorption capacity for the CEM structures of vehicle.