# Buckling Analysis of Interspersed Railway Tracks
## 4 Conclusions  
In this study, a 3D finite element model was developed to investigate the buckling behaviour of interspersed railway tracks. Many researchers have studied the buckling phenomena of timber sleeper tracks and concrete sleeper tracks. However, buckling analysis of interspersed tracks has never been conducted. Interestingly, interspersed railway tracks have issues of inconsistent stiffness and material properties, which are likely to increase the deterioration rate of the railway track due to uplift behaviour under a moving train. Nonetheless, interspersed tracks seem be beneficial in preventing track buckling compared with conventional timber tracks. The following key findings were revealed by the parametric studies and obtained results. * The \"1 in 2\" interspersed track possesses greater buckling strength than \"1 in 3\" and \"1 in 4\" interspersed tracks and timber tracks as more timber sleepers are substituted by concrete sleepers. Plain concrete sleeper railway track provides higher buckling strength than all other tracks. * The replacement of timber sleepers by concrete sleepers tends to improve buckling resistance. * Plain concrete track can significantly increase the buckling temperature by about 25%. * For weaker track lateral resistance, torsional resistance seems to significantly improve the overall resistance and increase the buckling temperature. There is no difference in buckling temperature when the torsional resistance is increased for weak track lateral resistance. It is important to note that the current research mainly focuses on parametric studies of interspersed railway tracks. Hence, linear eigenvalue analysis is best used for preliminary study, and the effects of various parameters and geometric change were not taken into account before reaching the buckling point. It is advisable to conduct nonlinear dynamic analysis to study the behaviour of railway tracks in both the pre- and post-buckling periods to obtain the complete structural behaviour. Although interspersed tracks could increase the deterioration rate of railway tracks due to stiffness inconsistency and uplift behaviour, an improvement of buckling resistance over timber tracks can be found in interspersed tracks. However, the replacement should be done carefully since this activity probably induces ballast disturbance, leading to a loss of ballast compaction. This study is the world's first to investigate the buckling behaviour of interspersed railway tracks, and these insights will enhance the inspection of lateral stiffness in railway systems and mitigate the risk of delays due to unplanned maintenance, thus paving a robust pathway for a practical impact on society. Figure 9: Buckling temperature difference relative to timber track: (**a**) Nominal torsional resistance value; (**b**) 50% reduction of nominal torsional resistance value; (**c**) 25% reduction of nominal torsional resistance value; (**d**) 25% increase of nominal torsional resistance value; (**e**) 50% increase of nominal torsional resistance value. **Author Contributions:** Conceptualisation, C.N. and S.K. ; methodology, C.N. ; software, C.N. and C.M.W. ; validation, C.N., and C.M.W. ; formal analysis, C.W. ; investigation, C.N., C.M.W. and S.K. ; resources, S.K. ; writing--original draft preparation, C.M.W. ; writing--review and editing, C.N. and S.K. ; visualisation, C.N. ; supervision, S.K. ; project administration, S.K. ; funding acquisition, S.K. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by European Commission, grant numbers: H2020-MSCA-RISE No. 691135. **Acknowledgments:** The authors are sincerely grateful to European Commission for the financial sponsorship of the H2020-MSCA-RISE Project No. 691135 \"RISEN: Rail Infrastructure Systems Engineering Network,\" which enables a global research network that tackles the grand challenge of railway infrastructure resilience and advanced sensing in extreme environments (www.risen2 rail.eu) [57].