Quantification of Lateral Forces in Concrete Crosstie Fastening Systems

Consistent increases in cumulative freight tonnages, combined with the move towards higher-speed intercity passenger rail operation, have placed greater demands on North American railroad infrastructure. Concrete crossties and fastening system components are known to fail at a wide range of life cycle intervals when subjected to demanding loading environments. Such failures can cause track geometry defects, require repetitive maintenance procedures, and present critical engineering challenges. Rail seat deterioration (RSD), the degradation of the concrete material beneath the rail, has been identified through surveys of North American Class I railroads as the most critical engineering challenge of concrete crossties. Shoulder/fastener wear or fatigue was identified through the same survey as the second most critical engineering challenge related to concrete crossties. Lateral forces transferred through the fastening system are thought to be a primary cause of degradation of insulators. The objective of this study is to quantify the demands on the insulator through analysis of the transfer of lateral wheel loads into the fastening system by measuring the magnitude of lateral forces entering the shoulder, a component of the fastening system adjacent to the insulator. The Lateral Load Evaluation Device (LLED) was developed at University of Illinois at Urbana-Champaign (UIUC) to quantify these forces. Data captured by the LLED will assist the rail industry in moving towards the mechanistic design of future fastening systems by quantifying lateral forces in the fastening system under representative loading conditions. Information gained through this study will also lead to a better understanding of the frictional forces at key interfaces in the fastening system. Preliminary results show that the transfer of lateral wheel loads into the fastening system is highly dependent on the magnitude of lateral wheel loads and the frictional characteristics of the fastening system.