Static and Dynamic Characteristics for Upward Buckling in Longitudinally Connected Slab Track Systems

The China Railway Track System (CRTS II) slab track—a longitudinally connected ballastless system—is widely used in China, with about 7365 km currently in service. In contrast with German ballastless tracks, which cover limited mileage and operate in milder climates, CRTS II slabs in China face large temperature swings and harsher environments, resulting in defects—especially upwarping. This study examines the critical instability mechanism of CRTS II track slabs under thermal loading. First, scale tests measured arch displacement and longitudinal push‑slab force while accounting for the rebar‑anchoring system. A mathematical model and simulation model were then developed. To study the dynamic characteristics for upward buckling in longitudinally connected slab track system, a track dynamic response analysis model was constructed that includes the effects of vehicle load, earthquake action, and temperature effect simultaneously. Rail vertical deformation increases nonlinearly with rising temperature, seismic intensity and train speed. When the seismic intensity reaches level 5 with a 60°C temperature rise, or levels 6–7 with a 50°C temperature rise, the track experiences upward buckling exceeding 2 mm, necessitating post‐earthquake inspection and repair. Adopting moderately reduced fastener stiffness, track slab elastic modulus, the elastic modulus of the CA mortar layer, enhances seismic resilience in ballastless track design.