The Influence of Track Stiffness on the Measurement of the Wheel Rail Contact Force

The measurement of loads acting on a railway line has become fundamental since the liberalisation of the access to the railway infrastructure (EC directive 440/91); in the years many design of track installation capable of measuring the vertical forces between wheel and rail have been developed. Dipartimento di Meccanica e Tecnologie Industriali of the University of Florence recently improved its reliable measurement system which is able to measuring the lateral (Y) force as well as the the vertical (Q) force at the wheel-rail contact while preserving mounting easiness. The system is based on the measure strains on the neutral axis of the rail by means of a set of strain gauges installed in a plug that is press fitted in a hole drilled in the rail web. As long as the reliable estimation of the average wheel-rail load requires the measurement and processing of the signals collected from a number of sensors, this paper investigates the influence of local track stiffness deviations on the quality of the estimation. A combined multibody-finite element approach is used to both overcome the limitations and get the advantages of the capabilities of the two methodologies.