17．Decision-making support system for planning replacement of wooden-sleepers with PC sleepers in curved sections

On curved lines with wooden sleepers, the lateral resistance of track panels is low, which can lead to excessive lateral displacement of the track, and rotting of sleepers which can then lead to derailment due to gauge-widening, therefore wooden sleepers are gradually being replaced with PC sleepers. Therefore, in order to prioritize which curves should have replacement PC sleepers first, a decision-making support system was developed to plan replacements considering the conditions of each curved section (Fig. 1).
This system takes into account curve and track structure characteristics, rolling stock and operating conditions and the deterioration of the track. It calculates which curves should be classed as high priority for installation of PC sleepers through evaluation of several running safety related factors, such as derailment due to gauge-widening, track panel displacement and extrusion or falling out of rail spikes.
Moreover, the system sets limit conditions, namely budget and length of track requiring replacement work, and helps to plan replacement work efficiently by selecting those curved sections which would most benefit in terms of safety improvement by having PC sleepers laid.
In addition, when wooden sleepers are partially replaced with PC sleepers (Fig 2), the system can calculate the appropriate distribution of PC sleepers to be installed etc. This function can be also used to set maintenance criteria in terms of admissible number of successive damaged sleepers, when carrying out sleeper inspections.
After trying the new system with data from a few line sections, it was found that compared to tackling wooden sleeper replacement by order of curve radius, starting with the smallest, the length of track work on could be reduced through this system by 15% whilst achieving the same improvements in safety (Fig.3).