Concept Development of a Short-Radius Guardrail System for Intersecting Roadways
Bob Bielenberg, John Reid, Ronald Faller, John Rohde, Dean Sicking, Eric Keller, Jim Holloway
This research study consisted of the concept development of a short-radius guardrail system for protection near intersecting roadways. The objective of the research study was to perform the preliminary analysis and design of a new short-radius guardrail system capable of meeting the Test Level 3 (TL-3) impact conditions of NCHRP Report No. 350 criteria. However, the research was only to include the development of a design concept and not the fabrication and subsequent testing. The research into the development of a new short-radius design, described herein, consisted of six parts: (1) a literature search; (2) a design space analysis; (3) construction of an appropriate NCHRP Report No. 350 test matrix in order to validate the design; (4) development and selection of a potential short-radius design; (5) computer simulation using LS-DYNA of the most promising design concept; and (6) selection of a final design along with recommendations and suggestions for future work. After considerable background research and investigations of various design considerations, a final design concept was developed that consisted of a thrie beam guardrail short-radius system with a 2,426-mm radius. The nose section has a pair of steel cables placed behind it to ensure capture of impacting vehicles in the event of rail rupture. The nose section and the first section of guardrail on each side of it are cut with horizontal slots in the valleys to aid in the capture of impacting vehicles as well as reduce the formation of large kinks as the guardrail deforms. The primary roadway side of the system terminates into an approach guardrail transition to a bridge rail, while the secondary roadway side of the system terminates into a FLEAT end terminal. Simulation of the design concept under NCHRP Report No. 350 test 3-33 impact conditions, a 100 km/h impact of a 2,000-kg pickup truck on the center of the nose at an angle of 15 degrees from the roadway, demonstrated that the design concept had significant potential for safely capturing and containing an impacting pickup truck. It was suggested that further development of the short-radius design concept be done including full-scale compliance testing.
Highway Safety, Guardrail, Longitudinal Barrier, Roadside Appurtenances, Short-Radius Barrier, Crash Test, Compliance Test, Intersection Protection