THE NATURE, MAGNITUDE, AND FREQUENCY OF LOADS AND FORCES APPLIED TO RAILROAD ROADBED

The magnitude, nature and frequency of loads imposed on railway roadbed by track structures and by traffic on the track structure is summarized for use by engineers in designing alternate types of roadbed construction. An SD-40 locomotive was studied to test severe loads Magnitude of reactions in the roadbed depends not only on the loads themselves but also in the spacing of the loads and the type and composition of support. In conventional track, the contact pressure on the bottom of a tie is not uniformly distributed either laterally or longitudinally. The total load on an individual tie depends on track conditions, size and distribution of load, and size, spacing and condition of the ties. There are traditionally two ways of handling impact loads, i.e. "equivalent static load" and "energy load." Of the two, "equivalent static load" is usually given for railroad situations and will be used here. Longitudinal loads come from inherent stress (from manufacture and laying of rails), reaction to locomotive traction, wheel flange friction and braking, thermal rail stress, and longitudinal component of train weight on grades. The longitudinal component of train weight can be calculated statistically knowing gross weight, grade, length of train, etc. Fortunately, this load is not concentrated but is spread out over a considerable distance. With conventional track construction the perpendicular component of train weight increases the frictional restraint of ties in ballast so that this is of little consequence. Longitudinal loads applied to the track by traffic have been the subject of considerable study in both this country and Europe. They are difficult to analyze because they are affected by so many variables, and uncontrolled variables at that. Transverse, or lateral, forces are particularly important since if they exceed roadway resistance they cause unstable alignment or buckled track and likelihood of derailment. Mathematical calculations show the rail reaction for the SD-40 on 122 lbs rail.

  • Corporate Authors:

    Chesapeake and Ohio Railway

    Terminal Tower, PO Box 6419
    Cleveland, OH  USA  44101

    Baltimore and Ohio Railroad

    Baltimore & Ohio Building, 2 North Charles Street
    Baltimore, MD  USA  21201
  • Authors:
    • WAY, G H
  • Publication Date: 1967-5

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 22 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00037597
  • Record Type: Publication
  • Report/Paper Numbers: Tech Rpt
  • Files: TRIS
  • Created Date: Dec 6 1976 12:00AM