Effect of Increasing Axle Loads on Rail Fatigue Life

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American Railway Engineering Association
This report presents the results of an investigation into the effects of increasing axle loads on the fatigue life of tangent, continuous welded rail (CWR). Two independent studies were conducted. The first utilized a statistical analysis technique, which obtained probability distribution curves for rail defect data. The second utilized a fatigue analysis methodology for the prediction of rail service life. Both techniques have shown good correlation between calculated results and service experience. For the first study, rail defect data was obtained from two mining railroads: one operating 100-ton car unit trains; the other 70-ton car unit trains. These were then compared with data from both a "typical" mixed freight traffic railroad and from FAST (l00-ton cars). For the second study, a rail fatigue life model was used to calculate the rail life under loadings that were representative of the same three types of operations. The results of both analyses show that increasing the axle loadings results in increased rail defect occurrences, with a corresponding decrease in rail fatigue life for tangent CWR. This reduction is by about 40% of the life of the rail, in million gross tons (MGT), when the loading is increased from 70-ton car (200,000 lb.)** to 100-ton car (236:000 lb.) loading conditions. This effect, which is seen for both heavy (132 lb.) and medium (119 lb.) rail sections is quite significant, and must be taken into account in any future studies and economic analysis.
Continuous welded rail (CWR), Fatigue analysis
Zarembski, A. M., “Effect of Increasing Axle Loads on Rail Fatigue Life”, Bulletin of the American Railway Engineering Association, Bulletin 685, Volume 83, November - December 1982.