United States Department of Transportation
i
Steel Post Version of Trailing-End Anchorage System – Phase I
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2020-12-17
[PDF-45.28 MB]
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Edition:Final Report: 2015 – 2020
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Abstract:In 2013, a non-proprietary, trailing-end anchorage system with a modified Breakaway Cable Terminal (BCT) was developed by the Midwest Roadside Safety Facility (MwRSF) for the Midwest Guardrail System (MGS). Although this trailing-end, guardrail anchorage system adequately met the American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) TL-3 safety requirements, the use of two breakaway wood posts was deemed to have several drawbacks. For state DOTs that primarily utilize steel posts, it was desired to develop a steel-post alternative for the BCT posts utilized in the trailing-end anchorage system. Thus, a critical need existed to develop a non-wood option to anchor the downstream end of the MGS. The objective of this research project was to develop a non-proprietary, steel-post version of the trailing-end anchorage system. The Universal Breakaway Steel Post (UBSP), utilized within the thrie-beam bullnose system, was found to be a viable option to replicate the breakaway performance of the BCT wood posts. Design concepts were developed from modification to the UBSP while utilizing the same basic cable anchor and ground line strut as used in the wood-post, trailing-end anchorage system to provide similar breakaway performance and anchorage capacity. Dynamic jerk tests were conducted to evaluate the breakaway performance of the end anchor posts and the capacity of the design concepts. Based on the dynamic jerk test results and input from Midwest Pooled Fund Program member states, a preferred steel-post, downstream anchorage design was selected and further developed. Final anchorage design included: (1) two breakaway steel posts; (2) a steel compression ground line strut between the two steel breakaway steel posts; (3) one steel anchor cable connecting the W-beam rail to the base of the end anchor post; and (4) a T-shaped, breaker bar attached to the end anchor post to facilitate the release and rotation of the end post. Recommendations for full-scale crash testing were provided for the preferred steel-post, trailing-end anchorage system.
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