DYNAMIC TRAIN TRACK/BALLAST INTERACTION - COMPUTER-MODELS AND FULL-SCALE EXPERIMENTS/

A numerical method has been developed by which the vertical dynamic be haviour of a railway track subjected to the loading of a moving train may be investigated. The interacting train and track are both modelled as dynamic systems and the compound train/track system is treated as a whole. In the track model, the rail is treated as a Rayleigh-Timoshe nko beam discretely supported, via railpads, by rigid sleepers. Below each sleeper, a rigid mass accounts for the mass of the ballast and th ose parts of the subgrade that participate in the vibration. The rigid mass is connected to the adjacent masses, to the foundation and to th e sleeper by linear springs and viscous dampers. The mass, stiffness a nd damping of these track components and also the sleeper spacings can be arbitrarily varied. The contact between the wheelsets and the rail is modelled by non-linear Hertzian spring elements. The model permits calculation of deflections, accelerations and forces in various track components, and also enables engineers to investigate how parameters such as train speed, axle load, bogie wheelbase, rail corrugations, wh eel flats and so on influence the track and vehicle components. To ver ify the computational method, two full-scale measurement programmes we re carried out on the Swedish West Coast Line in 1993 and 1995. Track parameters are determined by use of measured frequency response functi ons. Measured and calculated frequency response functions show accepta ble agreement. Variations in measured parameter values are discussed.