Train derailments resulting in hazardous materials releases from tank cars can have serious health, environmental, and economic consequences. Given the chaotic and complex nature of train derailments, quantifying the release probability of derailed tank cars is challenging. Statistical quantification of the safety performance of different tank car designs and tank car components in derailments has been conducted using an extensive historical database. However, these statistical probabilities are not a robust metric for new or novel tank car designs or materials because of the lack of data. Instead, analytical or simulation-based approaches are an appropriate alternative for these cases. These require an understanding of the underlying physics of derailment impact events and the dynamic behavior of derailed cars. Information on the
probabilistic impact load environment can be obtained by simulating a series of derailment scenarios that replicate derailment conditions.
An advanced computer model has been developed and partially validated that simulates derailment kinematics enabling estimates of the release probability of tank car components exposed to derailment forces to be estimated. In particular, the model develops probabilistic estimates of the resistance and demand for tank cars and their key components (i.e., tank heads, tank shells, top fittings, and bottom fittings). These models characterize the structural behavior of each tank car component in an impact scenario. They incorporate key elements, such as the derailment-caused impact forces, impact types, impact event characteristics, and tank car properties, to determine the quantities of interest at the level of an impact type affecting a component of a tank car. This model will be further validated and tank car release probabilities estimated using a design of experiments approach for a representative series of derailment scenarios. The validation procedure involves a series of primary and derived metrics to quantify characteristic dynamic behaviors of the train and derailed railcars, such as the extent of the derailment, the spatial dispositions of derailed railcars, their longitudinal and lateral spread, and their misalignment with the track.