Attenuation effect of material damping on impact vibration responses of railway concrete sleepers

In railway industry, high strength concrete has been adopted for track slabs and railway sleepers for more than half a century. Prestressed concrete sleepers (or railroad ties) are designed usually using high strength concrete (>55 MPa) in order to carry and transfer the wheel loads from the rails to the ground and to maintain rail gauge for safe train travels. In general, the railway sleepers are installed as the crosstie beam support in ballasted railway tracks. Statistically, they are subjected to impact loading conditions induced by train operations over wheel or rail irregularities, such as flat wheels, dipped rails, crossing transfers, rail squats, corrugation, etc. These defects can be commonly found during the operational stage of life cycle. The magnitude of the shock load depends on various factors such as axle load, types of wheel/rail imperfections, speeds of vehicle, track stiffness, etc. This paper demonstrates the investigations into the dynamic responses of in-situ prestressed concrete sleepers using high strength materials, particularly under a variety of impact loads. The nonlinear finite element model of full-scale prestressed concrete sleeper with the realistic support condition has been developed using a finite element package, STRAND7. It has been verified by the experiments carried out using the high capacity drop-weight impact machine and experimental modal testing. The experimental results exhibited very good correlation with numerical simulations. In this paper, the numerical studies are extended to evaluate the dynamic behaviors of high strength concrete sleepers modified by crumb rubbers to increase material damping coefficients. The outcome of this study can potentially lead to the utilization and practical design guideline of high strength concrete engineered by crumb rubber from wasted tires and plastics for prestressed concrete sleepers.