Diagnostic of flexural damage on railway prestressed concrete sleepers using dynamic modal responses

Flexural damages in railway prestressed concrete sleepers are often hidden from visual inspections during track monitoring and maintenance activities. Often, small cracks can sometimes be generated due to aggressive dynamic actions. These cracks indicate a level of serviceability of the railway sleepers. Severe cracks can impair rail gauge stability due to large rail inclinations. This gauge instability can cause train derailments, especially in curves and transitions where lateral train force incurs coincide with unstable two point contacts between wheel and rail. An attempt to develop a non-destructive diagnostic tool for structural health of prestressed concrete sleepers in railway tracks using the vibration responses has been established at the University of Birmingham, UK. The fundamental principle is to have better insight into the dynamic modal parameters of damaged sleepers. This paper therefore investigates the diagnostic of railway concrete sleepers based on vibration responses of railway prestressed concrete sleeper. Experimental modal analysis has been used to evaluate the modal parameter changes of the prestressed concrete sleeper in the frequency band between 0 and 2,000 Hz. The railway concrete sleepers have been subjected to ultimate static loading to stimulate structural failures. Dynamic modal parameters of the sleepers have been investigated before and after the flexural damage. Parametric comparison highlights meaningful changes in frequency response function, dominant frequencies and associated modal damping coefficients. This fundamental insight will establish a decision-making guideline for rail track engineers and managers to monitor and maintain structural integrity of railway track and its components.