Dynamic Effect on Vibration Signatures of Cracks in Railway Prestressed Concrete Sleepers

In general, cracks in structural members indicate a level of serviceability of the engineering structures. Usually a hairline crack can be detected by visual inspection, crack gauge, fibre optical sensor, or laser sensor. Recently, an attempt to develop a non-destructive tool for health monitoring of prestressed concrete sleepers in railway tracks using the vibration responses has been established at the University of Wollongong, Australia. However, the fundamental understanding of the dynamic effect due to the cracks in sleepers is insufficient. This paper investigates the dynamic effect of the cracks on the vibration signatures of the railway prestressed concrete sleepers. The modal analysis has been used to evaluate the modal changes in vibration characteristics of the prestressed concrete sleepers in the frequency band between 0 and 1,600 Hz. The sample cracks have been initiated by the impulsive forces attributed to the high capacity drop impact testing machine. Comparison of the modal parameters of the intact and cracked sleepers has been highlighted in terms of natural frequencies and modal damping. This understanding will lead to further development of the economical technology to evaluate the structural integrity of railway track and its components.