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Development of the MGS Approach Guardrail Transition Using Standardized Steel Posts

REPORT NUMBER

TRP-03-210-10

AUTHORS

Scott Rosenbaugh, Karla Lechtenberg, Ronald Faller, Dean Sicking, Bob Bielenberg, John Reid

PUBLICATION DATE

2010-12-21

ABSTRACT

A W-beam to thrie beam stiffness transition was developed to connect the Midwest Guardrail System (MGS) to a previously-approved thrie beam approach guardrail transition to bridge rail. This new stiffness transition was configured with standard steel posts commonly used by State Departments of Transportation. The system was crash tested and evaluated according to the Test Level 3 (TL-3) safety performance criteria specified in the Manual for Assessing Safety Hardware (MASH). BARRIER VII computer simulation modeling, in combination with post-in-soil bogie tests, was used to evaluate multiple transition configurations. The optimal configuration was the shortest design to successfully eliminate excessive pocketing and wheel snag. The approach guardrail transition was attached to Missouri's thrie beam and channel bridge railing system. Three full-scale crash tests were conducted. During the first test, the upstream terminal anchor post failed prematurely, thus causing a loss of rail tension which ultimately led to vehicle pocketing. After inspection, the upstream anchor post was found to have a large knot located on its tension face at groundline that led to the wood fracture and failure of the test. The test was rerun given careful attention to the quality of the BCT anchor posts to ensure that the system design strength could be met. Following the successful containment and redirection of both the 1/2-ton Quad Cab pickup truck (2270P) and the small car (1100C) test vehicles, the safety performance of the stiffness transition between the MGS and a thrie beam approach guardrail transition system, including an asymmetrical guardrail element, was determined to be acceptable according to the TL-3 evaluation criteria specified in MASH.

KEYWORDS

Highway Safety, Roadside Appurtenances, Crash Test, Compliance Test, MASH, Asymmetric W-Beam to Thrie Beam Transition, Longitudinal Barrier, Approach Guardrail Transition, TL-3, Steel Post, and Midwest Guardrail System (MGS)

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