Guidance for Raising Beam Guardrail Composite Blockout for Rail Height Adjustment (605311)

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Final Report Link:  Pendulum Testing on Composite Blockouts Raised on Steel Posts


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:
Al Hangul, P.E.
Civil Engineering Manager, Design Division
Tennessee Department of Transportation
James K. Polk State Office Building
505 Deaderick Street
Nashville, TN 37243-0348
(615) 741-0840
[email protected]


With recent changes/clarifications about appropriate height for beam guardrail, there are more and more existing locations identified where rail height is below the recommended heights. Pavement overlays create additional locations where this occurs. Raising the blockout on the post is a low-cost safety means to adjust the rail height; however, there are still some unknowns regarding how the rail system would perform when including use of composite blockouts.

The purpose of this research was to analyze W-beam rail performance when blockouts are raised on the posts as a means for adjusting rail height. Specifically, this research evaluated steel post with composite/wood blockout systems.

From comparison of energy plots, it appears that the system with wood blockouts was able to absorb more energy during the impact event in comparison to the systems which used proprietary composite blockouts – this was true during the impact in the baseline condition (when blockout was not raised on post), and in the case where blockouts were raised on posts. The wood blockouts remained attached to the post and were not fractured as a consequence of the first impact from the pendulum nose.

As a result of the pendulum tests on raised blockouts reported, the Roadside Safety Pooled Fund has decided to fund an additional project to full-scale crash test a complete guardrail installation with blockouts raised on posts. Conducting a full-scale crash test with a 2270P (pickup truck) vehicle should provide a better understanding of the performance of blockouts when raised on posts.