The Study on the Influence of Toe Load on the Failure of Railway Fastening System in a Thailand MRT Project

Abstract

The rapid expansion of railway network in Thailand imposes the need for the effective maintenance to ensure system reliability, availability and maintainability (RAM). In modern railway track work, different components, e.g. ballast, track plinth, fastening system, rail and etc. form a complex system. Each component is designed and customized for specific functions. Failure to fulfill their function will cause the system unable to perform expected task or even system break down. One critical component in the railway track work is the clip whose function is to properly maintain the rail in lateral and longitudinal position and at the same time allows some degrees of the deformation of the rail to accommodate daily thermal expansion. One typical criterion to ensure proper function of the fastening system is specified toe load values of the clips after track work installation. In the service, the clips are potentially subjected to both normal fluctuating load and high dynamic load, e.g. impact load due to track irregularities, welded joint and etc. which can cause fatigue failure. If the damage cannot be observed and corrected in time, the clip could break and yield serious consequences. Even though the track work is properly installed, toe load of clip could differ by more than 50% resulting in large difference in initial stress condition. Clips with high initial stress could be anticipated of fatigue failure in the service. This present work is intended to study the influence of toe load on fatigue resistance of clips. Based on measurement data performed on site in a MRT construction project in Thailand, both fatigue experiment and simulation were performed to evaluate the life time of clip. The finding from this experiment can be used as a guideline to schedule proper maintenance plane to ensure the structural integrity of railway track components.