Development of Universal Breakaway Steel Post for Bullnose Median Barrier

Abstract

A new fracturing-bolt universal breakaway steel post (UBSP) was developed and evaluated for use as a replacement for the controlled-release terminal (CRT) wood post currently used in the Thrie beam bullnose system. After numerous steel post concepts were investigated, a fracturing-bolt steel post was selected as the most promising design. The fracturing-bolt steel post successfully matched the strength and dynamic behavior of the CRT wood post in three impact orientations. The UBSP was incorporated into the Thrie beam bullnose barrier system and subjected to three full-scale vehicle crash tests according to the Test Level 3 guidelines provided in NCHRP Report 350. Test Designations 3–30, 3–31, and 3–38 were chosen to evaluate the performance of the Thrie beam bullnose system with UBSPs. All three full-scale crash tests demonstrated that the UBSP performed in a satisfactory manner in the bullnose system, as the vehicle was captured and safely brought to a controlled stop. On the basis of the successful completion of the three full-scale crash tests, it is recommended that the UBSP be considered a safe alternative to CRT posts in the original Thrie beam bullnose median barrier system. It is also noted that the performance of the UBSP suggests that it may have additional applications, including in long-span guardrail, end terminals, and guardrail in mow strips or encased in pavement.