Threshold Radius of a Ballasted CWR Curved Track: Curve Classification

Different codes and railways specify different maximum curvatures for their track systems. The curve-negotiating capability of the vehicle dictates the absolute minimum radius used on a track system; other factors may also be considered to decide the minimum radius. In this paper, a minimum radius labeled as the threshold radius is determined when a ballasted, continuously welded curved track would not move under the action of thermal load in an unladen track. Thus, the curve with the threshold or flatter radius would not require hot-weather or cold-weather patrolling or other measures to augment the lateral strength of the track. A formula is derived in this paper to determine the threshold value: the temperature limits at which hot-weather or cold-weather patrolling is to be enforced if the radius happens to be sharper than the threshold radius. Formulas are also used to determine the desirable temperature range for tamping. The paper also presents a review and analysis of the current literature to be able to choose a practical value for lateral resistance of monoblock concrete ties; it also presents a literature review on recently developed forms of concrete ties. A typical application is then presented to demonstrate the utility of the formulas. Finally, on the basis of the formulation and analyses, curves are then classified into three groups based on a maintenance point of view—Group I (least desirable), Group II (desirable), and Group III (most desirable). The research presented here will be useful for both design and maintenance engineers.