Improved Destressing of Continuous Welded Rail for Better Management of Rail Neutral Temperature

Abstract

Maintaining high, stable rail neutral temperatures helps prevent the buckling of continuous welded rail (CWR) track. Rail neutral temperatures are typically set high during installation (90°F to 110°F), but the large variations that develop during revenue service often lead to buckling-prone conditions. Readjusting or correcting for these variations requires CWR to be destressed with the use of procedures that do not always restore the desired target neutral temperature. As part of the Federal Railroad Administration's Track Systems Research program, the U.S. Department of Transportation's Volpe Center is investigating rail force and neutral temperature influences on track buckling. An analytic model for field applications has been developed to improve destressing and readjustment of CWR in both winter and summer conditions. The model has been validated in several field tests on instrumented CWR test segments under both high tensile and compressive force conditions. Both wood and concrete tie tracks were tested, and the rail longitudinal movement, rail gap, rail force distributions after rail cutting and welding, and readjusted neutral temperature were measured and correlated with the model predictions. The model and test results were used to develop a field tool for more effective destressing and readjustment of CWR. The tool provides the required removal lengths of anchors/fasteners, the rail gap size requirements when mechanical loads (rail-pullers) are used to adjust to the desired neutral temperature, and the required amounts of steel removal in summer when cutting rail out for stress relief.