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Investigating the Use of a New Universal Breakaway Steel Post




Steven Arens, Dean Sicking, Ronald Faller, John Reid, Bob Bielenberg, John Rohde, Karla Lechtenberg




A new fracturing-bolt, universal breakaway steel post was developed and evaluated for use as a replacement for the wood CRT post currently used in the thrie beam bullnose system. It was the intent that the new universal breakaway steel post would also become a replacement for wood CRT posts used in other guardrail systems. This research study focused only on a steel post for the thrie beam bullnose system. After investigating numerous candidate steel post concepts, bogie testing was used to select the most promising design, a fracturing-bolt steel post. The fracturing-bolt, steel post successfully matched the strength and dynamic behavior of the wood CRT post in three different impact orientations. Preliminary LS-DYNA simulation modeling was also performed to analyze the fracturing-bolt, steel post. Subsequently, the breakaway steel post was implemented into the thrie beam bullnose barrier system and subjected to one 2000P full-scale vehicle crash test according to the TL-3 of NCHRP Report No. 350. Test no. USPBN-1 demonstrated that the breakaway steel post did not perform satisfactory in the bullnose system as the pickup truck was not captured and later overrode the guardrail system. The fracturing-bolt posts did not absorb sufficient energy to safely capture and contain the vehicle. Post no. 2 did not break away quickly, thus causing the pickup to redirect more than observed in prior wood-post, bullnose testing. Based on the unsatisfactory results, two research plans were proposed for continuing the research and development of a breakaway steel post for use in bullnose barriers.


Highway Safety, Guardrail Posts, Wood Posts, Breakaway Steel Posts, Bogie Testing, Bullnose Barrier, Median Barrier, Crash Test, Compliance Test

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