Report Result

TRP-03-369-20

Scott Rosenbaugh, Ronald Faller, Nathan Asselin, Jason Hartwell

PUBLICATION DATE

2020-11-10

ABSTRACT

Approach guardrail transitions (AGTs) incorporate increased post and rail sizes, reduced post spacings, specialized buttress end geometries, and other roadway features to smoothly transition from deformable W-beam guardrail to rigid barriers. This transition in barrier lateral stiffness requires specific combinations of these components to function properly. Changing components, or even the addition or removal of a curb below the rail, can negatively affect the safety performance of an otherwise crashworthy system. However, recent full-scale crash testing has indicated that a properly-designed buttress at the downstream end of an AGT may be utilized with multiple thrie-beam AGT systems. Thus, the objective of this project was to develop a standardized buttress to reduce vehicle snag and be compatible with a wide variety of previously-developed, 31-in. tall, thrie-beam AGT systems, either with or without a curb. The standardized buttress was designed with a dual taper on its front upstream edge. A shallower lower taper was designed to mitigate tire snag below the rail, while a steeper upper taper was designed to prevent vehicle snag and limit the unsupported span length of the guardrail. This buttress design was evaluated in combination with a critical AGT (i.e., an AGT with lower stiffness than other crashworthy AGTs) without a curb, representing a worst-case scenario. The standardized buttress was successfully crash tested to the 2016 Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) safety criteria. Guidance was provided for both the attachment of the buttress to various crashworthy thrie-beam AGTs as well as how to transition the shape of the buttress to adjacent bridge rails or rigid parapets downstream from the AGT.

KEYWORDS

Highway Safety, Crash Test, MASH 2016, TL-3, Guardrail Transition, Thrie Beam, Concrete Buttress, Barrier Transition, Crashworthy

REPORT

TRP-03-369-20.pdf