Proposed Modifications to AASHTO Culvert Load Rating Specifications

The choice of load rating method may affect the transportation of goods and services over the nation’s highways by imposing load limits on routes that were previously unrestricted. For culvert load rating, engineers use the load and resistance factor rating (LRFR), load factor rating (LFR), or allowable stress rating (ASR) of highway bridges according to the AASHTO Manual for Bridge Evaluation. However, culverts respond to live loads differently than bridges as a result of surrounding soils. Moreover, the LRFR is calibrated based primarily on bridge response to gross truck weight, while culvert response should be calibrated based on a single axle or a single wheel. As a result, the current specifications may be either overly conservative or inadequate, which may lead to expensive replacements or upgrades, or premature deterioration or failure, respectively. Therefore, there is an immediate need to develop a load rating process for culvert structures to maintain an acceptable level of culvert reliability without unnecessary restrictions on commerce. The objective of this research was to propose modifications to the culvert load rating specifications in AASHTO Manual for Bridge Evaluation and revise the AASHTO LRFD Bridge Design Specifications accordingly. At a minimum, the research should address: (1) different culvert types, sizes, cover thicknesses, the effect of pavement, soil effects, and live loads; and (2) a comparison between LRFR, LFR, and ASR methods. The LRFR specification shall be calibrated based on proposed reliability indices, load factors, and load distribution.


  • English


  • Status: Completed
  • Funding: $500000
  • Contract Numbers:

    Project 15-54

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway & Transportation Officials (AASHTO)

    444 North Capitol Street, NW, Suite 225
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Dekelbab, Waseem

  • Performing Organizations:

    Michael Baker Jr., Incorporated

    100 Airside Drive
    Moon Township, PA  United States  15108-
  • Principal Investigators:

    Mlynarski, Mark

  • Start Date: 20150707
  • Expected Completion Date: 20190331
  • Actual Completion Date: 20190331
  • Source Data: RiP Project 37550

Subject/Index Terms

Filing Info

  • Accession Number: 01543474
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 15-54
  • Files: TRB, RiP
  • Created Date: Nov 15 2014 1:01AM