TTI Research Supervisor:
Chiara Silvestri Dobrovolny, Ph.D.
Associate Research Scientist
Texas A&M Transportation Institute
TAMU 3135
College Station, Texas 77843-3135
(979) 845-8971 [email protected]
Pooled Fund Technical Representative:
Kurt Brauner
Bridge Engineer Manager
Louisiana Department of Transportation
1201 Capitol Road
P.O. Box 94245
Baton Rouge, LA 79084-9245
(225) 379-1933 [email protected]
ABSTRACT:
A stacked W-Beam guardrail transition to a bridge rail has been successfully tested in accordance with the NCHRP Report 350 criteria with a guardrail height of 27-5/8 inches. This transition uses a nested W-beam to stiffen the rail and a W-beam rub rail to reduce the potential for snagging on the end of the bridge rail. Many states are raising the height of their w-beam guardrails to 31 inches to improve its performance. Several transitions have been tested for the 31-inch guardrails that use a thrie beam rail and a thrie beam to W-beam reducer section. A stacked W-beam transition is desired for the 31-inch guardrail systems as a simpler method of transition without unique rail elements.
Two possible 31-inch stacked W-beam transition designs were investigated to evaluate the crashworthiness of the test article with respect to NCHRP Report 350 crashworthiness criteria. Finite element computer simulation investigation suggests that both designs might not meet the NCHRP Report 350 crashworthiness requirements due to severe snagging of the vehicle against the rigid parapet to which the transition is connected. Snagging occurrence is related to the relative height of the vehicle frame rail which does not allow the frame to fully engage with the top nested rail sections during the impact event. As a consequence, with both 31-inch transition designs, the 2000P NCHRP Report 350 pickup truck vehicle frame rail and tire snagged against the rigid parapet in between the top rail and the rubrail.
