Railway Dynamic Load Factors Developed from Instrumented Wheelset Measurements

Abstract

Dynamic load factors (ϕ) relate the magnitude of vertical wheel-to-rail loads in operation (dynamic loads) to static loads resulting from the weight of the rail car and its contents, as a function of train speed. The ϕ equations are often used in the selection of rail steel and cross-sections (weight). Equations for ϕ have been put forth by the American Railway Engineering and Maintenance-of-Way Association (AREMA) and others. A limitation of the existing ϕ equations is that they have been derived from loads measured at instrumented sections of track and observe the many wheel loads but with constant track conditions. For this study, measurements of dynamic loads from two instrumented wheelset (IWS) as it conducted four passes over a 340 km section of track operated by a North American Class 1 freight railway through the Canadian Prairies. These measurements provided dynamic loads from one loaded freight car over various track structures at differing train speeds. This paper presents the IWS data sets and the variation of dynamic loads between multiple passes of the section of track studied, and the statistical distribution of dynamic loads. New ϕ equations are developed for tangent track and nontangent track (inclusive of bridges, grade crossings, curves, and switches).