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Guardrail Post Bolt Hole Size

Question
State	WI
Description Text	My question is about placing a slotted hole in the post flange that is larger than what was used in the crash test. This is shown on the attachment. Thanks.

System Performance Evaluation

System Types
Road Closure Gates
Thrie Beam Guardrails

Applications

System Features

Date September 17, 2014
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Attachment Slotted Holes.pdf

Response
Response (active)	In general, it is not a good idea to change a critical element of the design from its crash tested variation. An increased hole size in the critical front flange would reduce the capacity of the steel post to resist bending. Horizontal slots would exaggerate this reduction of post capacity, especially for those located closest to the base plate when moments are maximized. Of course, the overall effect that the slot versus hole has on a barrier system safety performance would depend on how conservative was the design initially. At this point, we have not been provided much information in terms of design/test level, construction details, and actual crash testing results. Further details and information would be needed to further explore this issue. Alternatively, it may be possible to integrate slots into the rail at splice and/or post locations to improve constructability without decreasing capacity. Thanks!

Response

Response
(active)

In general, it is not a good idea to change a critical element of the design from its crash tested variation. An increased hole size in the critical front flange would reduce the capacity of the steel post to resist bending. Horizontal slots would exaggerate this reduction of post capacity, especially for those located closest to the base plate when moments are maximized. Of course, the overall effect that the slot versus hole has on a barrier system safety performance would depend on how conservative was the design initially. At this point, we have not been provided much information in terms of design/test level, construction details, and actual crash testing results. Further details and information would be needed to further explore this issue.

Alternatively, it may be possible to integrate slots into the rail at splice and/or post locations to improve constructability without decreasing capacity.

Thanks!

Date September 19, 2014
Previous Views (122) Favorites (0)