Railroad Wood Tie Design and Behavior

The theory of an elastic beam on an elastic or spring foundation is reviewed and its implications to straight rail track examined as an introduction to tie design. Published data on railroad track performance are reassessed with emphasis on the design of the wood tie. Contradictions and inaccuracies which result in errors and questionable practices in present North American recommended design procedures are found. Improvements in design methodology are outlined which are consistent and dimensionally correct. For the new heavier jumbo freight cars present practice is shown to be marginal and fatigue failures are predicted to increase. It is concluded that the optimum length of ties to prevent centerbinding on standard gauge is theoretically 8½ ft ignoring the tie plate and 9 ft with a 12-in. tie plate on competent ballast support. Further improvements should be made by increasing tie width and maintaining or lowering the ratio of spacing to tie breadth.