Eurailmag - #15 - March 2007 - (Page 76)

Infrastructure GETZNER WERKSTOFFE SLEEPER PA D S I N T U R N O U T S O N B A L L A S T E D TRACK – MATHEMATICAL OPTIMIZATION ue to the complex geometries of turnouts, a considerably greater amount of work and expenses is needed for the track maintenance as compared to the regular track. In particular, a varying vertical rail deflection results from the differences in the stiffness of the track bedding in the travelling direction. This, in turn, results in additional stresses and subsidence on the track superstructure when trains pass by. The use of sleeper pads allows for significant improvements to be achieved in terms track stability and vibration reduction. The ballast is subject to lower loads, which increases the tamping intervals. As a result, the Life Cycle Costs (LCC) can be significantly reduced. A non-linear calculation model based on the Finite Elements Method (FEM) was developed in close cooperation with the Austrian Federal Railways (Engineering Services Dept.) and the engineering office Fritsch, Chiari & Partner ZT GmbH (FCP) to address this need. With the aid of this FEM model, Getzner Werkstoffe has the ability to situate the elastic Sylomer® or Sylodyn® sleeper pads in the various areas of turnouts in such a manner that sharp transitions in the stiffness of the track superstructure are reduced or prevented. This, in turn, facilitates safe, problem-free traffic across the turnouts, at high speeds as well. For example, sharp transitions in the stiffness in the crossing frog of the turnouts can be compensated by gradiating the stiffness of the bedding. Moreover, by distributing the stiffness under the short sleepers (after the last long sleeper) it is possible to reduce the swaying that occurs when trains pass through the turnouts. Hence, the subsidence areas turnouts are “smoothed out”. FEM-Model for turnouts with sleeper pads Measurements of vibrations have revealed substantial advantages in comparison to turnouts without sleeper pads: in particular there was a reduction in vibrations in the 40-50 Hz frequency range. Settling of the ballast bed can also be reduced even compared to turnouts with a moveable crossing frog. These positive experiences and the possibility of mathematical optimization using the FEM model have resulted in a standard design model for the Austrian Federal Railways. The trend for the future in the production of turnout sleepers is that the pads will be mounted directly during the manufacturing process. CONSTRUCTION Getzner sleeper pads are made of cellular polyurethane elastomers. These materials are characterized by the following properties: • low ratio of dynamic to static stiffness • durable elastic characteristics • mechanical resistance • volume compressible (no profiles or cavities are necessary to achieve low stiffness) Getzner elastic sleeper pads are constructed of several layers: The isolation layer is firmly attached to the bottom of the sleeper and determines the elastic properties of the support. The load distribution layer is in direct contact with the ballast. This layer operates as mechanical protection for the insulation layer and distributes the forces over a wider area. VIBRATION REDUCTION Measures reducing structure-borne noise are often necessary in densely populated areas due to the close proximity of rails lines and buildings. These measures hinder the propagation of vibration, which also helps to prevent secondary airborne noise in adjacent structures. Elastic sleeper pads represent a highly economical method of effective isolation against structure-borne noise. Sylomer® /Sylodyn® sleeper pads In recent years, for the purpose of testing, individual turnouts in Austria have been outfitted with a defined distribution of stiffnesses in the Sylomer® sleeper pads, for example in Baden (2002), Gunskirchen (2003) and Vöcklabruck (2004). Issue 15 EURAILmag Business & Technology

Table of Contents for the Digital Edition of Eurailmag - #15 - March 2007

SOMMAIRE
NOTICE BOARD
COATINGS
NEWS
SERVICES
INFRASTRUCTURE
HIGH-SPEED LINES
TUNNELS
PEOPLE
ROLLING STOCK
WEBSITE DIRECTORY

Eurailmag - #15 - March 2007

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