On Stress and Deformation Accumulation of Continuously Welded Rails under Cyclic Thermal Loading in High-Speed Railways

This paper focuses on the stress and deformation accumulation of continuously welded rails (CWR) in ballastless tracks under cyclic thermal loading, which could pose a potential threat to the stability and service life of CWR but related theoretical studies are yet to be conducted. Firstly, the nonlinear longitudinal resistance of fasteners (LRF) resulting from the CWR-rail pad contact interface is mathematically described by extending the classical Dhal friction model and verified via an in-door experiment. Both the hysteretic and softening properties of the LRF can be captured compared with the traditional ideal elastoplastic model. Most importantly, we originally propose a quasi-dynamic method (QDM) to tackle nonlinear static problems by extending an explicit numerical integration algorithm from the dynamics field to the statics. Afterwards, the quasi-dynamic equilibrium equations of CWR in the tunnel transition zone and on the simply-supported beam bridges subjected to thermal loads and LRF are constructed, and the reliability of QDM to obtain static responses is well-validated by existing analytical methods. Finally, the limitation of the ideal elastoplastic LRF model, distribution characteristics and accumulation process of rail longitudinal deformation and axial additional stress are fully unveiled. The current work is conducive to better recognition of the longitudinal mechanical behavior of CWR under cyclic thermal loads.