Crush Analyses of Multi-Level Equipment

Abstract

Non-linear large deformation crush analyses were conducted on a multi-level cab car typical of those in operation by the Southern California Regional Rail Authority (SCRRA) in California. The motivation for these analyses was a collision, which occurred in Placentia, CA, on April 23, 2002. The final deformed state of the leading cab car was unusual. This behavior contrasted with previous testing and analysis experience of single level equipment in collisions. This investigation explores the structural response of multi-level car structures. The structure of the multi-level equipment differs from single level equipment in that a significant change occurs in the load path from where load enters through the coupler and is subsequently reacted aft of the body bolster of the car. This change in load path results from a change in geometry of the car to accommodate quarter point doors and the upper level of the car. Load enters at the typical coupler height but descends to the lower platform level of the car through a transition structure. To better understand the influence of the varied geometry, a series of calculations were performed to obtain the force-crush characteristics and modes of deformation for the cab car subjected to a series of different initial conditions. Crush models were developed of both the lead and trailing end of the car, as well as the center section of the car. In addition to these sub-models, a full car model was constructed. Results from the sub-model analyses indicate that the longitudinal strength of the trailing end is comparable to that of the lead end, and the center section of the car is significantly stronger than either end. This suggests that crush will most likely occur at the ends of the car when it is overloaded. Initial conditions similar to the Placentia, CA accident were also investigated to better understand the atypical mode of deformation that occurred. These results indicated that the multi-level equipment can resist high force levels for longer crush distances than single level platform vehicles but will eventually experience softening behavior, which will result in focused crush at one end of a car.