Behaviour of GFRP Reinforced Concrete Railway Sleepers: Finite Element and Fibre Model Analyses

There is currently no guidelines for the design of concrete sleepers reinforced with glass fibre reinforced polymer (GFRP) bars. This project focused on analysing the suitability of concrete railway sleepers reinforced with glass fibre reinforced polymers (GFRP), with special attention being given to the detailed design of the GFRP reinforcement and appropriately analysing the developed sleeper design and behaviour in comparison with AS1085.14 design requirements. Prestressed concrete sleepers possess many characteristics which make it a more desirable sleeper material compared to other traditional materials such as timber and steel. However, the current problem within the railway industry is sleepers (of all materials) failing before their given design life. Corrosion of the steel is the main cause of failure associated with prestressed concrete. GFRP bars are corrosion resistant therefore, this project aimed to explore the suitability of concrete sleepers reinforced with GFRP bars, by theoretically investigating the flexural behaviour of the developed sleeper section under varying track and sleeper design parameters. Finite element analysis was first used to determine the effect which varying track parameters would have on the structural behaviour of the sleeper section and determine the maximum design bending and shear stresses the sleeper will be subjected to as a result of these track and sleeper parameters. The results indicated that variation of rail load application has a significant effect on the bending and shear behaviour of the sleeper section however, implementation of the rail load as a point load application is recommended to be retained. Additionally, it was found that support modulus has a significant effect on the bending, shear and deflection behaviour of the sleeper section, suggesting that this parameter needs to be incorporated as part of the simplified design equations in AS1085.14. With the maximum design stresses obtained from the first stage of analysis, fibre model analysis was then performed to determine the effect which varying design parameters and volume of GFRP reinforcement would have on the flexural behaviour of the sleeper section reinforced with GFRP. The results indicated that the concrete strength requirements specified in AS1085.14 are appropriate and should be adopted, whereas the specified concrete cover requirements should be investigated further when dealing with GFRP reinforcement. The results also highlighted that to satisfy flexural strength requirements, the recommended detailed design for the developed sleeper section will need to consist of two layers of reinforcement (12.7mm diameter bars) with 30mm cover and a concrete strength of 50MPa. The outcomes of this dissertation highlight that GFRP reinforced concrete sleepers can provide a sufficient design in relation to flexural strength requirements however, further investigation is required to determine the ultimate suitability of this proposed alternative sleeper design