Criteria for Restoration of Longitudinal Barriers

NCHRP Project 22-23, "Criteria for the Restoration of Damaged Guardrails," has effectively been completed by researchers at Virginia Tech. As part of this project, researchers surveyed the states to determine what, if any, formal guidelines they have for the maintenance of guardrails. The study determined that while some states did have guidelines for evaluating existing guardrails and determining whether maintenance was indicated, these guidelines were typically based on judgment and were not supported by underlying research. The objective of Project 22-23 was to develop guidelines to assist maintenance personnel in identifying levels of damage and deterioration to longitudinal barriers that require repairs to restore operational performance. To achieve this objective, the researchers evaluated for eleven damage and deterioration modes commonly associated with the standard strong steel post W-beam (modified G41S) guardrail; they evaluated these modes through a combination of component testing, pendulum testing, finite element simulation, and full-scale crash testing. From this testing, draft maintenance guidelines were developed. Final guidelines for the maintenance of longitudinal barriers will be presented in a final report, due to be completed in May 2010. It is anticipated that maintenance guidelines for cable barriers will be developed under NCHRP Project 22-25. The objective of this problem statement is to continue the work begun under NCHRP Project 22-23. While this initial project did groundbreaking work in evaluating the performance of barriers having damaged components, there were limitations to the work that could be undertaken in one study. Among the additional research needs are: (1) Evaluation of wood post systems - The 22-23 final report will include maintenance guidelines for strong-wood-post W-beam systems. However, as the testing done under 22-23 was limited to steel-post systems, there is a need to conduct similar testing and evaluation of wood posts and wood post guardrail systems to confirm that these guidelines are applicable to wood-post systems as well. (2) Overlapping damage modes - The evaluations under NCHRP 22-23 were limited to one damage mode at a time. Oftentimes, though, more than one mode of damage will be present in a given barrier. An example would be rail flattening in combination with rail deflection. There is a need to better understand the interaction between overlapping damage modes and how these would affect barrier performance. (3) Generic End Treatments - Maintenance guidelines for generic end treatments were presented in 22-23, but these were largely drawn from guidelines developed by state departments of transportation (DOTs). Similar to the issue with wood posts, these guidelines should be quantitatively tested and evaluated. (4) Damage to barriers near end terminals - A previously damaged rail element within the first 50 feet of rail in an energy-absorbing terminal may not properly activate the end terminal in a head-on crash. If these rail units are not straight, the rail element may lose column strength and be unable to resist buckling when impacted end-on. (5) Consideration of damage modes to other similar systems such as the recently developed Midwest Guardrail System, a generic W-beam guardrail system with a 31-inch mounting height. (6) It is anticipated that the research program will involve a combination of component testing, pendulum testing, and computer simulation of crash tests. Full-scale crash testing may be considered if necessary to validate the other methods of analysis, but will not be the focus of research. The following efforts are considered important to the successful completion of this research: (1) Review the experience of field maintenance staff using maintenance guidelines developed in NCHRP Project 22-23. (2) Identify damage assessment needs which will include the needs identified in the NCHRP 22-23 final report and any additional assessment needs chosen in consultation with the project panel. (3) Propose a research program to qualitatively and quantitatively assess the needs identified earlier in this problem statement. (4) Prepare an interim report that outlines the findings of the above efforts for review and comment by the project panel. (5) Upon panel approval, conduct planned analyses and supporting tests to develop the metrics for assessing longitudinal barrier damage, correlating them to safety performance. (6) Prepare a plan of full-scale crash testing necessary to fully validate the guidelines developed under this project. (7) Prepare a final report to document the research effort and recommended guidelines. Maintenance personnel are charged with making decisions as to when damaged guardrails needed to be repaired. Prior to NCHRP 22-23, only limited guidance was available to guide such decisions, and there was no supporting research available on which to make such judgments. NCHRP 22-23 has addressed this need, in part, but additional work remains to be done. This project will result in additional guidelines directed at garage-level maintenance employees who make the day-to-day decisions regarding the need to repair guardrail systems. The payoff of improved decisions by these staff will be the ability to focus their maintenance efforts on those barrier installations that truly need repair to maintain their performance under vehicular impacts.<p> </p>


  • English


  • Status: Proposed
  • Contract Numbers:

    Project 22-28

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  USA  20590

    American Association of State Highway & Transportation Officials

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

    National Cooperative Highway Research Program

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

    Niessner, Charles

  • Start Date: 20100618
  • Source Data: RiP Project 26558

Subject/Index Terms

Filing Info

  • Accession Number: 01463900
  • Record Type: Research project
  • Source Agency: National Cooperative Highway Research Program
  • Contract Numbers: Project 22-28
  • Files: TRB, RiP, USDOT
  • Created Date: Jan 3 2013 2:32PM