A Collision Dynamics Model of a Multi-Level Train

Abstract

In train collisions, multi-level rail passenger vehicles can deform in modes that are different from the behavior of single level cars. The deformation in single level cars usually occurs at the front end during a collision. In one particular incident, a cab car buckled laterally near the back end of the car. The buckling of the car caused both lateral and vertical accelerations, which led to unanticipated injuries to the occupants. A three-dimensional collision dynamics model of a multi-level passenger train has been developed to study the influence of multi-level design parameters and possible train configuration variations on the reactions of a multi-level car in a collision.This model can run multiple scenarios of a train collision. This paper investigates two hypotheses that could account for the unexpected mode of deformation. The first hypothesis emphasizes the non-symmetric resistance of a multi-level car to longitudinal loads. The structure is irregular since the stairwells, supports for tanks, and draglinks vary from side to side and end to end. Since one side is less strong, that side can crush more during a collision. The second hypothesis uses characteristics that are nearly symmetric on each side. Initial imperfections in train geometry induce eccentric loads on the vehicles. For both hypotheses, the deformation modes depend on the closing speed of the collision. When the characteristics are non-symmetric, and the load is applied in-line, two modes of deformation are seen. At low speeds, the couplers crush, and the cars saw-tooth buckle. At high speeds, the front end of the cab car crushes, and the cars remain in-line. If an offset load is applied, the back stairwell of the first coach car crushes unevenly, and the cars saw-tooth buckle. For the second hypothesis, the characteristics are symmetric. At low speeds, the couplers crush, and the cars remain in-line. At higher speeds, the front end crushes, and the cars remain in-line. If an offset load is applied to a car with symmetric characteristics, the cars will saw-tooth buckle.

Post Test Review of a Single Car Test of Multi-Level Passenger Equipment

“…The displacement on the independent axis is from the car body accelerometers. Figure 18 shows that the multi-level car and the single level car have a similar initial peak force of approximately 3x10 6 lbf at a displacement of 3 inches. After the initial peak in force, the single level car crushes at a relatively low force of 5x10 6 lbf.…”

“…A heuristic model, based on the collision in Placentia California, shows that the mode of deformation is dependent on the collision velocity [4]. Collision dynamics models demonstrate the importance of the trailing cars in determining the mode of deformation [6].…”

“…The finite element models suggest crush at two locations, both the leading end and the gooseneck [5]. Collision dynamics modeling suggests that the leading end or a combination of the leading end and the gooseneck will crush during the test [6,8].…”

Crush Analyses of Multi-Level Equipment

“…The force-crush characteristics determined from these analyses have been used as input to several collision dynamic models used to study the Placentia, CA accident, as well as the Glendale, CA accident [10,11]. The car was designed to meet all current industry standards and Federal regulations.…”

“…The circle on the left accounts for the manner of load application from the trailing coach cars and concrete embankment that interacts with the rear trucks on the cab car as the collision ensues. In order to simplify the train collision dynamics, which are covered in greater detail in a companion paper [10], the mass of the moving freight train was reduced to an effective weight of 300,000 lbm. The rigid locomotive included the coupler and draft gear.…”