A Review of Parameters Affecting Rail Break Gap Size Using Analytical Methods

Abstract

Management of continuous welded rail (CWR) stress is critical to maintaining railroad safety. To successfully manage the stress-state of the rail, knowing the rail neutral temperature (RNT) is critical. RNT is defined as the temperature at which the net longitudinal force in the rail is zero. If the RNT is set too low/high then the rail would buckle/pull apart and create unsafe operation conditions. To reduce unsafe operating conditions, researchers have previously developed guidelines for managing RNT maintenance activities. However, there remains an opportunity to improve these guidelines given there have been 24 derailments caused by buckled track between 2009 and 2018. Therefore, a research program has been established to improve current guidelines. It is difficult to manage the stress of CWR because the RNT is difficult to quantify, and has been shown to change over time, tonnage, or as a result of maintenance (tamping, etc.). Further, rail breaks may lead to local changes in RNT, leading to the need for RNT readjustment. Current guidelines estimate prevalent RNT before a rail break/cut based on rail gap size. Therefore, as a part of a broader research program, this paper reviews an analytical method presented by Kerr that quantifies rail break gap length and identifies the roles of longitudinal track resistance and stiffness. Results indicate that plastic track displacements driven by longitudinal track resistance dominate, and the longitudinal track stiffness has limited influence. This paper also identifies limitations of this analytical approach and documents recommendations for improved models.

Review of Critical Factors Influencing Longitudinal Track Resistance

“…Lateral resistance is an absolutely critical parameter required to perform an accurate buckle analysis and has been studied by many authors previously, a few of whom that can be cited here are Mohammadzadeh et al ( 7 ), Kerr ( 8 ), Allen et al ( 9 ), Esmaeili et al ( 10 ), and Shenton ( 11 ). However, longitudinal resistance, which has been studied less, is also considered to be one of the most critical parameters required for longitudinal load propagation analysis ( 12 – 14 ) and RNT maintenance practices ( 15 – 17 ) in CWR track. Together, both the lateral and longitudinal track resistance provide stability to the track structure.…”