Direct Fixation Track Design

Abstract

Design principles for direct fixation track must address a wide range of parameters and issues. Described are the basic design principles related to loading and how they are applied for direct fixation track. There is a presentation of the principles and methods for determining loads imposed on fasteners for an application, determining fastener spacing, determining anchor bolt and insert characteristics (shear strength, pull-out strength), and implementing the fastener support design. Additionally, design approaches that improve construction with reduced costs, fundamental stipulations that should be included in direct fixation construction specifications, and direct fixation track tolerances (mating tolerances, construction tolerances) are addressed. Although the principles apply to any direct fixation system, the study concentrates on track systems using fully bonded fasteners with elastic rail clips, a common arrangement. A useful reference is proposed for analysis of existing installations as well as new installations.