Cargo response to railcar impact and tiedown load analysis

An analytical study of the loads produced during coupling of railcars carrying heavy shipping containers is presented. The structural model of the impact event is represented by a lumped-parameter technique. Each discrete mass lump possesses longitudinal, vertical, and rotational degrees of freedom. The resulting computer simulation provides for nonlinear railcar coupler stiffness and linear damping forces in the coupler and container tiedowns. Results include response to parametric variations in container weight, impact speed, and tiedown stiffness. Container dynamic response and tiedown loads are found to depend heavily on these parameters. Also, railcar bending and subsequent vertical motion are shown to be important contributors to these responses. When experimentally substantiated, the model developed can serve as a useful tool in the design and evaluation of shipping container tiedown structures