Analysis of tapered, adhesively bonded, insulated rail joints

Abstract

Adhesively bonded insulated rail joints are used to electrically isolate sections of track into discrete blocks to detect the positions of trains, and are sometimes useful in detecting rail breaks. Recent advances in high-strength rails allow for the use of higher-weight cars. With this increased axle loading of the freight lines, bonded rail joints are encountering early breakdown through either electrical or mechanical failure. Service lives as short as 12-18 months have been reported on some rail lines, significantly lower than the lifetime of other railway components. The cost of replacing the joints has significantly increased the desire for a joint with improved durability. Commercially available bonded rail joints are typically double butt-strap joints consisting of two steel reinforcing joint bars, bonded to the rails with an epoxy adhesive that may contain a fibreglass or aramid cloth layer. This paper investigates a tapered bonded joint that was proposed to reduce the high stresses that can result in the more typical butt-strap joint configuration. The first type of analysis models the rails and joint bars as beams, and the adhesive and ground as distributed elastic springs. Approximate solutions are obtained with the use of the Rayleigh-Ritz method. The finite-element method is used in the second type of analysis. Deflections, bending moments, and stresses are obtained. Based on these analyses, tapered insulated joints should provide some advantages over conventional insulated rail joints, such as lower deflections, bending moments, and shear stresses in the adhesive.