Regarding the replacement of steel reinforcement in pre-stressed concrete sleepers with composite rebars

At present various under-rail designs made from different materials are used on railways worldwide. As the national requirements for railways are becoming stricter due to growing traffic speeds, axle loads, and loading, the improvement of under-rail structures and materials in relation to these requirements is an urgent task. The study presents an analytical review of literature data on the types of railway track substructures and track structure materials used in Europe and worldwide, features of construction and production technology of wooden, glued timber, reinforced concrete, metal, composite sleepers, their standardized characteristics (strength, frost resistance, cracking resistance, durability, electrical resistance) and test methods for their determination, peculiarities of interaction with ballast. The analytical review shows that many disadvantages of concrete sleepers reinforced with composite reinforcement can be overcome. Their advantages include high corrosion resistance of the reinforcement, which allows a rational approach to the assignment and provision of crack resistance of sleepers. An analysis of the mechanism of electric current flow through a concrete sleeper was carried out. It was shown that replacement of steel wire reinforcement with non-electric composite reinforcement will make it possible to increase the electric strength of a sleeper, to reduce the current flows and electrical corrosive phenomena even for the operation of a sleeper with cracks. As a result of the calculations and analysis of the stress-strain state of sleepers performed using the finite element method, it was found that sleepers reinforced with steel wire and composite reinforcement are subject to the same compressive strength. Reducing the pre-stressing force of the composite reinforcement even to the point of being completely eliminated leads to an increase in tensioning forces and cracked sleepers, but does not lead to concrete crumbling in the stiffened areas.