Risk Assessment and Update of Inspection Procedures for Culverts

A new culvert inspection rating system was developed by the Ohio Department of Transportation (ODOT) and described in their 2003 Culvert Inspection Manual. The Ohio Research Institute for Transportation and the Environment (ORITE) developed a proposed rating system and tested it and the ODOT system on 60 culverts in 8 of 12 ODOT Districts across the state: 25 concrete culverts, 25 metal culverts, and 10 thermoplastic pipe culverts. The ODOT rating system rates 16 items on a 0 to 9 point scale, while the proposed system considers 30-33 items on the same 0 to 9 point scale. This scale represents an improvement over the 4-point (good, fair, poor, critical) scale in use in Ohio since 1982. The inspection results indicate that concrete culverts have a service life limited to 70-80 years, and metal culverts have a service life limited to 60-65 years. A multivariable regression analysis of the inspection data found that for concrete culverts, age and pH were significant factors in both rating systems, while drainage flow abrasiveness was also a significant factor in the ODOT system. For the concrete culverts, the ODOT system had a higher adjusted R-squared value and detected more significant factors; the adjusted R-squared values were 0.45 and 0.39 for the ODOT and proposed systems, respectively. A larger sample size would have improved the level of accuracy and the number of significant factors. The multivariable analysis of the metal culvert inspection data found that the significant factors were age, rise, and culvert type. Abrasiveness, pH, and flow velocity were also significant factors in the proposed system. The proposed system had a higher adjusted R-squared value and detected more significant factors; the adjusted R-squared values were 0.75 and 0.43 for the proposed and ODOT systems, respectively. The sample size of thermoplastic culverts was too small to permit a meaningful statistical analysis. A risk assessment of the culverts was conducted based on the NCHRP Report 251 using an adjusted overall culvert rating. The adjusted ratings for the concrete culverts were between 2 and 6 in both systems, with one culvert requiring a highest priority of maintenance immediacy of action and two requiring high priority maintenance immediacies of action; the rest were rated between 4 (priority for the current season) and 6 (schedule work by the end of next season). Results for the metal culverts were similar, with the exception that only two culverts required a high level of maintenance immediacy of action. The adjusted ratings for the thermoplastic pipe culverts ranged from 6 (add to scheduled work by end of next season) to 9 (no repairs needed) in the ODOT system and from 5 (place in current season schedule at first reasonable opportunity) to 9 (no repairs needed) in the proposed system. A number of innovative culvert rehabilitation techniques were discussed, including slip-lining, cured-in-place pipe, invert replacement using concrete or gunite, filling voids, and repairing sleeves for localized problems.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Bibliography; Figures; Photos; Tables;
  • Pagination: 428p

Subject/Index Terms

Filing Info

  • Accession Number: 01001477
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/OH-2005/002
  • Contract Numbers: State Job No. 14813(0)
  • Files: NTL, TRIS, ATRI, USDOT, STATEDOT
  • Created Date: Jun 27 2005 12:03PM