Long-term behaviours of railway prestressed concrete sleepers due to shortening parameters

Long-term behaviours of railway prestressed concrete sleepers are critical parameters in determining durability and performance functions required for predictive maintenance management. The time-dependent behaviours vary largely due to their creep, shrinkage and elastic shortening responses. Many investigators in the past have proposed various material models to predict shortening effects but those were mostly applied to general reinforced concrete members. In contrast, prestressed concrete design has adopted those models for predicting the structural behaviour of prestressed concrete structures such as long span bridges, stadiums, silos and confined nuclear power plants, etc. Such the constitutive models have led to a concern of practitioners whether those existing predictive models could be realistically applied to prestressed concrete. Due to high initial elastic shortening in prestressed concrete, the creep and shrinkage effects should be critically re-evaluated in flexural members. This paper presents a comparative investigation using a variety of methods to evaluate shortening effects in railway prestressed concrete sleepers. Three common design codes have been considered, including European Standard EUROCODE2, American Standard ACI and Australian Standard AS3600-2009. The study results show that EUROCODE2 and AS3600 are very coherent and consistent. It also shows that ACI code will need to be revised to take into account various environmental factors. The insight of this study will help rail track engineers to improve predictive maintenance model of railway infrastructure and to minimise time spent on inspection activities, which are critical part of asset operations.