Fatigue life modelling of railway prestressed concrete sleepers

Railway sleepers, which transfer wheel loads to the formation, are an essential component of railway track systems. Prestressed concrete is the most commonly used type of railway sleepers around world. Crushing is a common damage (under resultant compressive stress) in concrete sleepers, which is attributable to excessive flexural, shear, pre-stress and bond actions. Dynamic impact loading conditions are often the cause of failure in the concrete sleepers. However, accumulated damage due to cyclic loads can also cause concrete crushing. Most previous research has investigated the impact load characteristics and the ultimate limit states of prestressed concrete railway sleepers. There is a knowledge gap with respect to serviceability limit states and fatigue failure of prestressed concrete sleepers. This study presents new results of extensive numerical, analytical, and experimental investigations aimed at predicting fatigue lives under cyclic loads. A numerical study validated by 30 full-scale experimental tests is executed and extended to assess fatigue limit states, while theoretical fatigue analysis methods based on S-N curve and Miner linear cumulative damage are additionally introduced for benchmarking. This paper is the world's first to demonstrate a remaining fatigue life assessment for prestressed concrete sleepers and benchmark with the theoretical methods. Parametric studies are conducted to unprecedentedly illustrate influences of support conditions, dynamic load distribution, and track stiffnesses on the remaining fatigue lives of prestressed concrete sleepers. This paper highlights the rationales associated with the development of fatigue limit states. The insights will provide design flexibility and improve railway sleeper maintenance and inspection criteria.