The effect of heavy haul train speed on insulated rail joint bar strains

Abstract

This paper investigates the effectiveness of train speed restrictions on the performance of Insulated Rail Joint (IRJ) joint bars, for typical train speeds utilised on heavy haul rail networks (20–90 km/hr). The work presented in this paper was prompted by a series of premature IRJ failures on Iron Ore heavy haul lines, in the Pilbara region of Western Australia, via cracking of the IRJ joint bars. This failure mode is characterised by partial, or complete failure of one or both of the IRJs connecting joint bars through fatigue crack initiation and propagation through the joint bar steel section. Train speed restriction is an approach commonly implemented by railway operators, as a risk mitigating control when travelling past failure prone IRJ locations. Field testing of in-service IRJs has been conducted. Strain gauge, sleeper displacement and wheel load measurements were obtained and analysed, via regression analysis, to investigate the influence of train speed on joint bar strains. This analysis clearly indicates that there is not a strong relationship between train speed, and joint bar strains, over the observed speed range of 20–90 km/hr. This result suggests that speed restrictions provide little or no benefit in reducing IRJ joint bar strains. While this result is consistent with theory presented in the literature, it is in contrast with typical operator practices. The data presented in this paper also indicate that there is a significant variability in both the strains developed in IRJ joint bars, and vertical sleeper displacements, between the installation locations monitored. For the two sites, the variability in peak bending strains was of the order of 40–45%. The analysis presented in this paper indicates that this variability is not related to differences in train speed.

Keywords:

• Insulated rail joint
• fatigue
• strain gauging
• joint bar
• rail

Acknowledgements

The authors would like to acknowledge the contribution of Mr. Michael Courtney (formerly Rio Tinto Iron Ore), Mr. Michael King, Mr. Kevin Kong and Prof. Manicka Dhanasekar of the Queensland University of Technology for their assistance with this paper.