New method will optimize car design for safer hazmat transport by rail07/23/2013
By Leslie Sweet Myrick
Transportation and structural engineering researchers are teaming up to develop an analytical method to measure the safety performance of railroad tank cars. Their techniques will be used to establish new industry standards to ultimately reduce the risk of transporting hazardous materials (hazmat) by rail.
“Although 99.998 percent of rail hazmat shipments reach their destination without a release caused by a train accident, potential tank car releases from train accidents could lead to severe consequences, especially if they happen in highly populated areas,” said M. Rapik Saat (BS 03, MS 05, PHD 09), a research assistant professor in the Rail Transportation and Engineering Center (RailTEC).
Saat and his colleague Christopher P.L. Barkan, professor and executive director of RailTEC, are working with Junho Song and Paolo Gardoni, both associate professors in structural engineering, to understand how new tank car designs will perform in accidents.
“A series of catastrophic tank car accidents in the 1960s and early 1970s led to several new safety features and the compilation of databases of information to measure and predict the safety of cars in service,” Barkan said. “As these databases were expanded and refined, it became possible to assess which combinations of changes in tank car safety design were most likely to maximize safety benefits. As part of a project we are finishing up during summer 2013, we updated a statistical model to evaluate tank car safety design using all the new accident information gathered since 1995. We were able to provide significant insight into the effects of some train operational factors, such as speed, that may be related to potential safety improvements that were not previously recognized because of a lack of quantitative information.”
While statistical models have been useful to evaluate existing tank car designs, the ongoing interdisciplinary collaboration between CEE’s railroad and structural engineering groups will pave the way for development of an analytical model to bridge statistical and analytical modeling (i.e. finite element analysis) approaches. For example, the interdisciplinary approach adds the ability to assess potential benefits of using new steel materials and/or structural configurations.
Tank car safety design optimization needs to consider the tradeoff between safety and efficiency, Saat said.
“For example, if you increase a tank car’s thickness, you may make it safer, but you decrease its capacity, and therefore may need more tank cars to carry the same amount of material. Our goal is to help industry find the optimal designs,” he said.
The development of this new analytical model is driven by industry and will be used for policy making.
“For example, with a new tank car design, they will do physical testing and finite element modeling to come up with the puncture energy and then translate the puncture energy to determine potential rate of release with a certain level of uncertainty,” Saat said. “This will advance the industry’s risk-based decision making to ultimately reduce the risk of transporting hazmat by rail.”
The work is a collaborative effort between government agencies and private industries involved in hazmat transportation in North America and is sponsored by the Association of American Railroads, Railway Supply Institute, American Chemistry Council, Chlorine Institute and Fertilizer Institute. CEE graduate students Laura Ghosh and Xiaonan Zhou have contributed to the project as well as Stephen Kirkpatrick from Applied Research Associates and Todd Treichel of the RSI-AAR Railroad Tank Car Safety Research and Test Project. At least one structural engineering student will also join the project team this fall.
The first phase of the new analytical model is expected to be completed in 2014.
Photo: A tank car built by Trinity Industries to the new standards with thicker shell and head and lower-profile protective housing. Risk and optimization models from CEE researcher Rapik Saat’s Ph.D. dissertation work were used to identify potential enhanced tank car designs to transport toxic inhalation hazard materials. These were later used by the U.S. Department of Transportation to develop hazardous material tank car regulations in 2009.