Business Profile
Rail vehicle crashworthiness: the performance of bodyside windows
All requirements that a joint Independent Glass and RSSB research project developed are now embedded in the Railway Group Standard GM/RT2100 Issue 5
F
or some years there had been concerns about certain aspects of the performance of train bodyside windows in collision conditions. Following the accident at Ufton Nervet, RSSB initiated a research project, T424, to attempt to improve the performance of bodyside windows in collision scenarios, if that was possible. From the T424 research and a detailed review of accident data, it became clear that in addition to the requirements of the standard of the time, GM/RT2456, bodyside windows in rail vehicles had to perform three additional critical functions in crash and post-crash conditions:
• first – prevent passenger ejection • second – prevent dangerous and undesirable objects or elements entering the vehicle including the small missile scenario from GM/ RT2456
• third – permit timely access by rescuers It was also important to consider the risk of injury to those working on the line-side from flying dice of glass if windows were broken on vehicles travelling at speed. Instances had occurred where multiple windows had been broken where dices of glass had bounced between
passing vehicles. Therefore, researchers recommended that measures were introduced which mitigated against these scenarios.
The research delivered very specific measures that for the first time were designed to represent a case where a passenger may be thrown against a window unit during a collision or in an overturning event. For these measures to be valid even if the glass may have been struck by debris from the collision, prior to being struck by a passenger, a sequential series of tests are required to be performed, all on the same degraded window unit. All requirements that the research developed are now embedded in the Railway Group Standard GM/RT2100 Issue 5.
An innovative glazing company Very early in this project the research team realised that it was essential to partner with an innovative glazing company, experienced in the rail industry and able to assist in meeting the demanding new requirements. Independent Glass, the leading UK manufacturer of glass products for the UK rail industry was approached to assist. The research team, impressed by its
technical ability and proactive attitude and range of test equipment, partnered with the company for the project. While it was recognised that the implementation of the new requirements represented a significant increase in measures designed to improve occupant passive safety on rail vehicles, it was also essential to take account of the inherent initial vagaries in the physical properties and performance of glass. Due to these inherent characteristics, while calculations are useful, physical testing can show poor correlation with predicted stress methods (including finite element analytical techniques) in the vitally important areas of highest stress. The ambient operating temperatures specified also needed very careful consideration as the performance of the laminating interlayer was recognised to vary significantly at extremes of vehicle operating temperature. IG calculated the maximum and minimum temperatures for both the external toughened and inner laminated panes of the glazing unit and factored in such considerations as wind chill (caused by train motion), solar gain and ambient temperature within the passenger cars. After consultation with RSSB the temperatures that were established led to requirements for pre-
December 2013 Page 115
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