Load Environment of Rail Joint Bars – Phase II, Joint Bar Service Environment and Fatigue Analysis

Detailed analysis of measured bending strains shows that the foundation deflections have the most significant effect on the magnitude of strains. All other factors, such as track type, track geometry, and fastening systems, have a less significant effect on strain levels. Fatigue analysis of the current and proposed candidate materials indicate that most joint bars may have a significantly longer fatigue life. The joint bar fatigue failures seen in service are likely from surface material discontinuities created as a result of manufacturing processes and mechanical notches induced during handling. Another factor that potentially affects the fatigue life is deteriorated foundations under rail joints. Significant residual stresses exist in as-manufactured joint bars. These stresses may affect the joint bar failures in negative or positive ways depending on the nature of service-induced stresses at a particular location. Instead of increasing the size of joint bars, managing residual stress appears to be an economical option to increase the strength of joint bars.