Crack resistance of reinforced-concrete sleepers with elastic rail fastening systems without base-plate

The article presents the main results of complex experimental and theoretical research into the crack resistance and the limit state of reinforced-concrete sleepers with elastic rail fastening systems without base-plate. The objective of this study is to uncover reasons for the cracks and other breakages during operation, demonstrate their importance, and produce a set of recommendations for prevention of the most serious defects. The research also involved statistical analysis of the defect factor for sleepers, and determined the number of defects by type according to track layout, traffic density, tonnage transported, concrete grade and other characteristics based on the results of full-scale research of track sections and surveys from maintenance specialists. The full-scale research was made on rail sections under standard operational modes and on a test track section of straight and curved elements with sleepers of concrete grades C32/40, C35/45 and C40/50.The study was based on numerical methods, modelling of the stress-strain behaviour of the track, and estimation of the performance of sleepers with cracks.The method used incremental-iterative algorithms to consider the elastic plastic properties of materials, solve contact problems in operation of rail fastening systems, and also reveal the structural nonlinearity of joint action for track elements. The method was realized in LIRA-SAPR software on the basis of Building Information Modelling (BIM) and the Finite Element Method (FEM).The results were verifiedby experimental research into the sleepers under static and dynamic loads with estimation of crack development in terms of concrete grades, deformation modulus, rigidities of the ballast layer and the sub-grade, position of the reinforcement and other characteristics.