Cable Barrier Literature Review

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Final Reports & Technical Briefs from Mid- America Transportation Center Mid-America Transportation Center 2002 CABLE BARRIER LITERATURE REVIEW Brian A. Coon Ronald K. Faller John D. Reid Follow this and additional works at: https://digitalcommons.unl.edu/matcreports Part of the Civil Engineering Commons, and the Transportation Engineering Commons This Article is brought to you for free and open access by the Mid-America Transportation Center at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Final Reports & Technical Briefs from Mid-America Transportation Center by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. CABLE BARRIER LITERATURE REVIEW Submitted by Brain A. Coon , M.S.C.E., P.E. Graduate Research Assistant Ronald K. Faller, Ph.D., P.E. Research Assistant Professor John D. Reid, Ph.D. Associate Professor MIDWEST ROADSIDE SAFETY FACILITY University of Nebraska-Lincoln 1901 "Y" Street, Building "C" Lincoln, Nebraska 68588-0601 (402) 472-6864 MwRSF Research Report No. TRP-03-118-02 July 10, 2002 Technical Report Documentation Page 1. Report No. 2. 3. Recipient’s Accession No. TRP-03-118-02 4. Title and Subtitle 5. Report Date Cable Barrier Literature Review July 10, 2002 6. 7. Author(s) 8. Performing Organization Report No. Coon, B.A., Faller, R.K. and Reid, J.D. TRP-03-118-02 9. Performing Organization Name and Address 10. Project/Task/Work Unit No. Midwest Roadside Safety Facility (MwRSF) University of Nebraska-Lincoln 11. Contract © or Grant (G) No. 1901 Y St., Bldg. C Lincoln, NE 68588-0601 12. Sponsoring Organization Name and Address 13. Type of Report and Period Covered Midwest State’s Regional Pooled Fund Program Final Report 2002 Nebraska Department of Roads 14. Sponsoring Agency Code 1500 Nebraska Highway 2 Lincoln, NE 68502 15. Supplementary Notes 16. Abstract (Limit: 200 words) A literature review of cable barrier systems. 17. Document Analysis/Descriptors 18. Availability Statement Highway Safety, Cable Barrier Systems, Three Strand No restrictions. Cable, Roadside Appurtenances 19. Security Class (this report) 20. Security Class (this page) 21. No. of Pages 22. Price Unclassified Unclassified 19 DISCLAIMER STATEMENT The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Federal Highway Administration nor State Highway Departments participating in the Midwest States Regional Pooled Fund. This report does not constitute a standard, specification, or regulation. ACKNOWLEDGMENTS The authors wish to acknowledge several sources that made a contribution to this project: (1) the Midwest State’s Regional Pooled Fund Program funded by the Connecticut Department of Transportation, Iowa Department of Transportation, Kansas Department of Transportation, Minnesota Department of Transportation, Missouri Department of Transportation, Montana Department of Transportation, Nebraska Department of Roads, Ohio Department of Transportation, South Dakota Department of Transportation, Texas Department of Transportation, and Wisconsin Department of Transportation for sponsoring this project; and (2) the University of Nebraska-Lincoln for matching support. Cable Barrier Literature Review ABSTRACT – A literature review of cable barrier systems. 1 LITERATURE REVIEW Research on cable barriers has been performed in two areas: testing for theory and design and compliance testing. FHWA policy requires that all roadside appurtenances such as traffic barriers, barrier terminals and crash cushions, bridge railings, sign and light pole supports, and work zone hardware used on the National Highway System meet the performance criteria contained in the National Cooperative Highway Research Program (NCHRP) Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features (1). Cable barrier height is measured from the ground to the center of the top cable; post spacing is measured from centerline to centerline of the posts, and impact angles are measured with respect to the roadway tangent and not with respect to the barrier. 1.1 Prior Cable Barrier Studies In 1967, Jehu and Laker determined that the height of a cable barrier was critical in the barrier’s performance (2). If the cables were too low, they could be ridden over; if they were too high, they could slide over the hood of a small car. A restricted number of tests, which proved unsuccessful, were performed with a two-cable barrier system. Until 1968, cable barriers in Canada, the United States, and Great Britain consisted primarily of a single cable mounted on wooden posts (3, 4). In the late 1960’s, Graham et al., with the New York State Department of Public Works, Bureau of Physical Research, performed a six-year study revising all of their standard barrier designs for roadsides, medians, and bridges. Graham determined that the best post for cable guardrail systems was a standard 3I5.7 post with three-¾ in. steel cables. A barrier height of 30 inches with a 3-inch spacing, a 16-foot post spacing, the utilization of a spring tension compensators, and the implementation of 6”x6” soil plates were adopted as the NY standard. MwRSF Report TRP-03-118-02 1 July 10, 2002 Graham also performed a test on a three-cable bridge rail. In this test, the car impacted the barrier, was not redirected, and broke nearly all of the lightweight posts off near the base and came to rest with the cables across the windshield. Between 1967 and 1968, a series of impact tests were carried out on cable barriers for rural highways by the Ontario Department of Highways (5). It was determined that when penetrations of the barrier of approximately six feet can be tolerated, satisfactory control of the vehicle can be maintained. The importance of keeping the wire ropes their original distance apart to minimize snagging was noted, and that the post stiffness plays a significant role in barrier deflection. In 1987, the Southwest Research Institute (SwRI) performed NCHRP Report 230 compliance testing on a modified G1 cable barrier system transitioning into a standard 4-ft flare BCT (W-beam) terminal incorporating a 37.5-ft parabolic curve (6, 7, 8). Initial testing was with a 2126 kg (4690 lb) sedan impacting at 94.7 kph (58.9 mph) and 27.3°. The impact location was at the transition from cable barrier to the BCT, post 18 on the cable system. The initial test failed NCHRP Report 230 guidelines. The system was retested at 24.4°, which passed NCHRP Report 230 guidelines. The system was then tested along the LON with a 2150 kg (4740 lb) sedan impacting at 94.3 kph (58.6 mph) and 25.0°, which also passed NCHRP Report 230 guidelines. In 1989, SwRI performed NCHRP Report 230 compliance testing on a standard G1 cable barrier system with 4 lb/ft Franklin posts (9, 10, 11). The cable barrier design, originally from the South Dakota Department of Transportation incorporated steel posts with trapezoidal soil plate as intermediate posts. The initial impact was with a 2040 kg (4500 lb) vehicle at 100 kph (60 mph) and 25° impacted 0.6 m (2 ft) downstream of post 11, which failed due to structural adequacy of the system. Identical testing repeated 3.0 m (8 ft) downstream of post 11 passed NCHRP Report 230. Subsequent testing of a 895 kg (1974 lb) vehicle at 98.8 kph (61.4 mph) at 21.2° was also successful. In 1990, The New York State Department of Transportation examined their cable barrier terminal ends (12). The terminal was redesigned due to snagging of small vehicles in departure MwRSF Report TRP-03-118-02 2 July 10, 2002 impacts. The new terminal concept, which included at 45° cable turndown and a slip-base end support was adopted. In 1993, Laker examined a new cable barrier design that utilized four ropes at two heights with the lower pair of ropes interwoven between the posts (13). Standard U.K. tests with a 1500- kg (3308 lb) car impacting at 113 kph (70 mph) and 20° showed that this design met the U.K. Department of Transport regulations. Further tests with a 750-kg (1654 lb) car at the same speed and angle demonstrated that rope heights are no longer critical: the fence could be installed on non-hardened surfaces, reducing the cost of installation. Yang et al. undertook a project to determine the causes and extent of slackening in cable barriers and propose corrective actions (14). During the 1979 New York State Department Highway Safety Review, almost every cable installation in New York was found to have insufficient tension. Results from field and laboratory tests indicated that cable barrier installations continually lose tension and the need to re-tension periodically is not reduced by using prestressed cables. Mak et al. evaluated the G1 cable barrier system in 1994 at the Texas Transportation Institute (TTI) (15). The G3 cable barrier complied with testing as specified by NCHRP Report 350 test level 3. In 1992 and 1995, Yang, Bruno, and Kenyon examined the effects of cable tension on cable guardrail performance (16, 17). It was determined that guardrails with insufficient tension may deflect excessively on impact, but that tension losses of 200 lb can be tolerated. In order to ensure proper tensioning in the cables, the following steps were recommended: • Pre-stressing cables to minimize initial creep • Tensioning the spring compensators during the installation process • Pro-rating the existing tensioning tables for smaller temperature-spring compression intervals to provide extra initial tension for some runs (making tension loss less critical) • Revising anchor placements and backfill requirements to reduce movement. Kenyon determined that cable stretch, post settlement, post tipping, spring-compensator MwRSF Report TRP-03-118-02 3 July 10, 2002 failure, accident impacts, poor installation procedures, turnbuckle movement due to vibration, and anchor movement both contributed to the reduction in tension of cable guardrails.

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