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Ragged edges in the guardrail slot

Question
State
Description Text This is a picture from our field review. You can see the spur on this brand new GR just installed. I initially thought it was a rare anomaly. However we noted other locations on new installations a significant distance from this project.

You were saying these ragged edges can cause a focus point for the stress and recommend they be filed smooth. This appears that the slot just was not punched clean. I assume this slot was produced by the manufacturer and I guess if the field crew had to correct them, the manufacturer would be hearing from his client the contractor.
Keywords
  • Guardrail
Other Keywords none
Date October 7, 2014
Attachment guardrail slot.jpg


Response
Response During the early development of the MGS, we fabricated field slots on site by drilling two holes spaced apart and cutting out the area between with a jig saw. At times, there would be a few rough areas or stress risers where the cuts met up with the radii. During crash testing, we observed some tearing around the slot when the bolt head pulled through the rail slot. I recall that we later required the use of a small die grinder to pass around the slot to remove any leftover burrs and smooth the slot. From this experience, we realized that the fabrication of the slot should not include rough/sharp edges or burrs in order reduce concerns for tears initiating in this region. See page 32 of the attached TRR from 2007. It is preferred that we have clean, smooth slots in the rail and near the bolts.
Date October 8, 2014


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