Loading limits can make track design simpler and reduce capital costs
New work to define lateral loading limits was required. Track design needs to consider a range of loads representative of current and future traffic, and a range of dynamic loading conditions, and is not a straightforward process.
Lateral loads requirements are typically defined based on limit values contained in existing standards and previous experience. Different interpretations of the standards have the potential to result in under or over-specification of track system design.
RSSB had previously commissioned research T1073 Loading Requirements for Track Systems to develop requirements for the design of track systems. This had completed analysis for vertical loading, but further research was now required.
Through the Strategic Partnership with the University of Huddersfield, a review of lateral loading limits in a range of standards were compared. Simulations were carried out to assess the requirements for lateral loading under a range of conditions.
These values are based primarily on the type of railway and rolling stock combination (axle loads), and are strongly influenced by the layout of the track (curvature).
The findings from previous research (T1073) and this research (COF-UOH-59) were synthesised, and recommendations made to inform, and provide guidance, to track designers. To help the identification of more appropriate limit values used in design, a draft framework was proposed for track design purposes considering three combined vertical and lateral load cases. It proposes a systematic way to derive limit values.
A more flexible approach to track design, that avoids over-design without negatively impacting whole life costs, could significantly lower capital costs. This is likely to have the largest benefit on routes operating lighter rolling stock.
Clear guidance on how to calculate track system requirements would provide clarity for designers and enable consistent and quicker decision making. These guidelines and recommendations help designers in those processes.