Continuous Welded Rail Track Buckling Safety Evaluation
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Date
2015-10
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Addis Ababa University
Abstract
Continuous welded rails (CWR) are rails that are welded together to become long continuous members. With the introduction of CWR several problems caused by traditional tracks have been solved, but the stability of the track is highly affected by change of temperatures and vehicle load.
Since expansion of the rails is hardly possible in CWR-track, a temperature increase and vehcle load will result in high compressive stresses and track buckling may occur. Therefore the Volpe Center, Foster-Miller, Inc. (FMI), research over the past 20 year develops versatile computer analysis software called CWR-SAFE for solving track buckling. The program incorporates both the deterministic and probabilistic analysis modules of CWR-BUCKLE, CWR-INDY, and CWR-RISK into one Windows based buckling safety evaluation package. This paper presents results of the application of CWR-BUCKLE software model for evaluation of CWR track buckling safety. Buckling can be explosive or progressive. Explosive buckling is characterized by equilibrium jumps between the two critical temperatures (identified as Tbmax and Tbmin) on the buckling response curve. In progressive buckling no distinct critical temperatures maximum and minimum exist, this usually occurs for weak track conditions. The deterministic approach will decide whether the CWR track with given parameters will buckle out or not. If it does not buckle, the “safety assurance” in terms of a buckling margin of safety can also be evaluated.
A sensitivity study has been performed showing the significance of the different parameters in buckling safety of the CWR track with respect to the detail effect of each parameter. Notably, the model accounts for all the important parameters influencing track buckling researched up to date by railway companies. Buckling safety graph is prepared by choosing lateral resistance as a primary variable in the determination of the safe allowable temperature increase with the other (secondary) parameters set at their average or nominal values.
As a conclusion of the investigations, several parameters have a significant impact on the buckling temperatures, Tbmax and Tbmin. The most important parameters are the temperature values and the lateral track resistance. When maximum rail temperature rise and Peak Lateral Resistance reduced, buckling will occur. It is important to note that the results presented represent trends and sensitivity influences for a set of fixed parameters. For a specific track type or condition, actual representative parameters should be used for buckling safety evaluation.
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Keywords
CWR-track, Buckling Safety, sensitivity Analysis, Buckling Temperature