Design, Development, and Qualification of New Guardrail Post

Abstract

The basic design concepts for strong-post w-beam guardrail systems were developed more than 30 years ago. Although the vehicle fleet today differs significantly from vehicles for which the systems were designed, those systems are still in widespread use. One of the changes in the vehicle fleet with the most influence on the performance of guardrails and other safety barriers is the emergence of pickup trucks and SUVs. These vehicles are heavy and have relatively high centers of gravity, so in addition to overloading the guardrail, such vehicles are highly unstable during redirection and are likely to roll over. One of the most serious problems with these systems is the front impact-side wheel snagging on the guardrail posts. Conventional post types used in strong-post guardrail systems consist of either large wooden posts or steel I-beam section posts, both of which are unforgiving when impacted by a wheel. Recently, HALCO, LLC, developed the HALCO X-44 post, a guardrail post that is lightweight, strong, and designed to be used in strong-post w-beam guardrail applications as an alternative to conventional post types. The X-44 post was designed to be more forgiving when crashed into by the wheel of a vehicle, yet strong enough to limit guardrail deflection under NCHRP Report 350 Test Level 3 impact conditions. In this study the HALCO X-44 post was evaluated in a length-of-need section of w-beam guardrail. A finite element model of the guardrail system was developed, and the finite element program LS-DYNA was used to assess its performance under NCHRP Report 350 Test 3-11 impact conditions. A full-scale crash test was subsequently conducted after favorable results from the finite element analysis. The system successfully passed the safety requirements of NCHRP Report 350 for Test Level 3. This paper discusses the evaluation procedure and presents results of the HALCO X-44 post and guardrail system analysis.