Long-term mechanical behaviour of CRTS III ballastless track-simply supported girder system under permanent load coupling action

A CRTS III ballastless slab track-simply supported girder system (girder-track system) was established to investigate the rail deformation, vertical irregularity of the track quality index (VITQI), and longitudinal stress in the girder-track system under the coupling action of concrete shrinkage, creep, and uneven pier settlement. The results indicated that the rail deformation caused by the coupling action was largely consistent with the linear superposition of deformations caused by the individual actions. After two years, the VITQI exceeded the specified requirements due to concrete shrinkage and creep. This situation occurred when the single-pier and double-pier settlements surpassed 2.74 mm and 2.36 mm, respectively. The long-term stress in the girder-track system from concrete shrinkage and creep aligned with that from the coupling action. At 20 years, the longitudinal compressive stress in the top slab of the girder significantly increased at the base plate gaps, reaching a maximum of 3.5 MPa and a growth rate of 17.7%. In contrast, the compressive stress at other locations decreased. The base plates, except at the girder ends, remained compressed, with a maximum stress of 1.85 MPa. Additionally, the coupling action increased the void area between the base plates and the SCC at the girder ends.