Development of a Fatigue Load for Railway Bridges

Steel railway bridges have an enviable record when examining service life. Steel bridges built in late 19th and early 20th centuries are mostly still in service. While many steel railway bridges are more than a century old, this compares favorably with highway bridges which are replaced after 50 years of service. While the age of these bridges is admirable, knowing how long they will continue to serve is a question without a simple response. One issue for the railways is the lack of a "railcar" configuration for design/rating used for fatigue which provides a standard for comparison of capacity for the bridge and demand for railcars. Without context of a standard for comparison, it is difficult to compare which bridges may need further evaluation or reduced inspection interval.   The objective of this research is development of a load model that serves as both a design load and a rating load to model fatigue behavior on railway bridges. Currently, the Cooper E Load is used for both maximum effects and fatigue loading. The Cooper E Load is challenging as a fatigue vehicle since it consists of closely spaced axles and a uniform load. This does not resemble the actual characteristics of rail equipment. Actual equipment and its ability to generate stress range cycling is not reflected in the Cooper E Load. Another outcome of the research is an examination of railcar loadings and train composition practices allowing estimation of fatigue cycling for existing and past railcar loads.   An advantage for railway bridge design results from the design approach. The method used in North America is published in the Manual for Railway Engineering by the American Railway Engineering and Maintenance-of-Way Association (AREMA). The use of Allowable Stress Design (ASD) combined with stringent deflection requirements allows the use of virtual designs. The necessary minimum section modulus can be directly calculated which allows modeling of stress ranges due to passage of typical trains that a bridge will have experienced. The virtual sections allow any conceivable load pattern to be analyzed. The results will be combined with bending moment theory to determine a load configuration which is representative of actual loads and can be used as a reference for comparison of railcars and bridges to know demands and capacities.   The creation of a fatigue load model for railway bridges has multiple ways to provide benefit for the railway industry. A fatigue load used for design and rating of fatigue connections will provide more consistency. The application of the fatigue load for use in establishing a fatigue rating system for railroad bridges will provide the commonality of a measurement tool like the Cooper E Load. This commonality extends within and between the railway companies, and extends to regulators in their ability to oversee the maintenance and safety of the railways.


  • English


  • Status: Active
  • Funding: $100000
  • Contract Numbers:

    Project 45

  • Sponsor Organizations:

    Safety IDEA

  • Project Managers:

    Fitzpatrick, Velvet

  • Performing Organizations:

    Purdue University

  • Principal Investigators:

    Connor, Robert

  • Start Date: 20201103
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01757150
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 45
  • Files: TRB, RIP
  • Created Date: Nov 4 2020 10:23AM