RTR 4/2010 6 1 Measured frequency spectra In order to answer the question, what kind of dynamic movements occur in the ballasted tracks, numerous vibration velocity measurements under traffic load were taken two years after the Hanover-Würzburg high speed line was put into operation in 1991. Frequency spectra of rail and sleeper were recorded in vertical direction during the passage of six ICE 1 trains at about 250 km/h under the coaches. The 6 measured spectra as well as the energetic mean value can be seen in Fig. 1. The measured graphs show several peak values and much lower values in the frequency range between 0 and 1000 Hz. In the peaks most energy is transmitted and the greatest wear is initiThe wear is mainly caused by movement of the sleepers in the ballast bed. Each ballast stone has initially a sharp-edged shape with rough surface. With time the sleeper movement leads to a smooth and rounded stone, which no longer can stabilise the track system. How to explain the strong wear of the track? This question is answered by the analysis of measurement results on a ballasted high speed track in comparison with calculated results. The measurement results are given by vibration velocity spectra of rail and sleeper during the passage of a high speed train. In the following, we take an ICE 1 train on the Hanover –Würzburg 250 km/h high speed line in Germany as an example. This line is fitted with ballasted tracks with prestressed concrete monobloc sleepers (B 70, 2.60 m long, mass 300 kg). The calculated results are developed from two mathematical models, one for the unloaded track und a spatial one with a wheel set on the two rails of the ballasted track. By applying the dynamic system analysis, a simplified but accurate mathematical model has been developed, which describes the most important dynamic characteristics of ballasted tracks. Thereby it is possible to design permanent ways in future, which are dynamically less sensitive for excitations by traffic. And so it is possible at last to optimise the dynamic properties of ballasted tracks, considering the design speed of the track. Frequencies of the ballasted track Realizing the fact that the ballasted track in high speed lines has half the life time of standard tracks we should ask the questions if on the one hand everything is done correctly and on the other hand which dynamic load is transmitted to the track. Scientific researcher, Former member of BZA DB AG, Munich ulf-pahnke@starnberg-mail.de Dr.-Ing. Ulf Pahnke Expert imb-dynamik, Inning imb-dynamik@t-online.de Dr.-Ing. Norbert Breitsamter Managing director, licensed expert for construction dynamics imb-dynamik, Inning imb-dynamik@t-online.de Dr.-Ing. Frank H. Müller-Boruttau Fig. 1: 1/3rd octave vertical vibration velocity spectra of rail and sleeper on ground during 6 passages of ICE 1 passenger wagons with 250 km/h and the energetic mean value (black). Velocity in mm/s eff., SLOW.
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