Abstract
This paper describes a newly developed measurement technique of the dynamic pressure distribution on a sleeper bottom induced by running trains with high frequency of up to several thousand Hertz using a special sensing sleeper equipped with ultra-thin-type impact force sensors. The sensing unit comprises a PC3-type mono-block concrete sleeper fitted with a large number of sensors. Attached to the sleepers whole undersurface is a solid mass made up of 75 thin impact force sensors (80 mm ? 80 mm ? 2 0 mm). Each impact force sensor has a main body and cover members. The main body, made from piezoelectric film (PVDF) and silicone rubber, has solid cover plates on both surfaces of the main body. The cover plates transmit impact force to the main body through multi-contact loading, which prevents breakage of the sensor itself from a running trains impact loads. The sleeper sensory performance was tested in a fullscale field experiment performed on a railway line. The results confirmed that the newly developed techniques are beneficial for measuring dynamic interaction within the boundary layer between a sleeper and an assemblage of ballast grains.