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Installation of MGS Long Span on Arched Culvert

Question
State	WI
Description Text	We have an installation proposed for the MGS long span across an arched culvert. The long span was chosen as the arched culvert limited the embedment depth. However, the culvert has a secondary issue in that the CRT posts are against the culvert headwall. What are your thoughts on this type of installation?

System Performance Evaluation

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Road Closure Gates
Thrie Beam Guardrails

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Date May 2, 2016
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Attachment sd-14b43 B-47-212.pdf

Response
Response (active)	We are concerned that placing the CRT post against the headwall may adversely affect the performance of the breakaway post and the overall behavior of the long span. CRT’s do dissipate some energy through soil rotation and placement of the post against the headwall will affect that rotation significantly. In previous situations like this we have recommended a minimum offset of 1 ft between the back of the post and the headwall to allow for that rotation. The only other option I can think of is to use the MGS weak post system. However, it is unlikely that we can get those posts embedded sufficiently over the top of the culvert arch. Thus you would need to move the line of the guardrail closer to the slope and attach the weak posts to the culvert directly.

Response

Response
(active)

We are concerned that placing the CRT post against the headwall may adversely affect the performance of the breakaway post and the overall behavior of the long span. CRT’s do dissipate some energy through soil rotation and placement of the post against the headwall will affect that rotation significantly.

In previous situations like this we have recommended a minimum offset of 1 ft between the back of the post and the headwall to allow for that rotation.

The only other option I can think of is to use the MGS weak post system. However, it is unlikely that we can get those posts embedded sufficiently over the top of the culvert arch. Thus you would need to move the line of the guardrail closer to the slope and attach the weak posts to the culvert directly.

Date May 5, 2016
Previous Views (143) Favorites (0)