Midwest Guardrail System for Long-Span Culvert Applications
Bob Bielenberg, Ronald Faller, John Rohde, John Reid, Dean Sicking, Jim Holloway, Erin Allison, Karla Lechtenberg (Polivka)
Long-span guardrail systems have been recognized as an effective means of shielding low-fill culverts. These designs are popular due to their ability to safely shield the culvert while creating little additional construction effort and limiting the damage and repair of the culvert when compared to other systems that attach posts to the top of the culvert. However, previous long-span designs were limited by the need to use long sections of nested guardrail to prevent rail rupture and the need for large lateral offsets between the barrier and the culvert. The MGS long-span guardrail described herein eliminates those two shortcomings by applying the benefits of the Midwest Guardrail System (MGS) to a long-span design. The MGS long-span increased vehicle capture and stability through increased rail height, limited the potential for pocketing and wheel snag through the use of CRT posts adjacent to the unsupported span, and greatly increased the tensile capacity of the rail through the movement of splices away from the posts and the use of shallower post embedment. These features allowed the system to be developed without the use of nested guardrail and with a minimal barrier offset that places the back of the guardrail posts even with the front face of the culvert. Two full-scale crash tests were conducted on the MGS long-span according to the Update to NCHRP Report No. 350 requirements for TL-3 test designation no. 3-11. Both tests were conducted with the heavier 2270P vehicle in order to generate higher rail loads and dynamic deflections. The MGS long-span design met all of the safety requirements of the Update to NCHRP Report No. 350. The MGS long-span guardrail's ability to perform safely without nested rail and a minimal barrier offset make this new barrier a very functional and safe option for protection of low-fill culverts.
Guardrail, Culverts, Long-Span Guardrail, Midwest Guardrail System, Highway Safety, Longitudinal Barriers, Roadside Appurtenances, Crash Test, Compliance Test
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