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Down Stream Anchor TRP-03-279-13

Question
State	UT
Description Text	Utah created a down stream anchor standard drawing according the TRP-03-279-13 document for the Wisconsin DOT Project MGS with Standard Downstream Anchorage System. Our local fabricator has asked if a different strut can be used other than the strut that was tested with this system. If that is a possibility I have attached a detail sheet of the proposed strut for your review and comment.

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Road Closure Gates
Thrie Beam Guardrails

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Date March 16, 2017
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Attachment Strut & Yoke Assembly (1).pdf

Response
Response (active)	The ground strut shown in the attached detail is similar to ones tested with previous end anchorage designs that were evaluated under NCHRP 230 and NCHRP 350. Similar anchor struts have also been observed in use with previous proprietary end terminal designs. While these struts may have worked in previous designs, their performance with the MGS system is unknown. Early in the development of the MGS, the foundation tubes were extended and the overall anchorage capacity was increased to accommodate higher anchor loads for MASH testing as well as the increased angle of the cable anchor used for the 31" height of the barrier. As such, the anchor capacity of the MGS end anchorage has increased over previous trailing end anchors. Thus, I cannot guarantee that the attached strut detail has sufficient structural capacity to work in the MGS downstream anchorage. Additionally, I am not aware of any current terminal designs using that specific strut that have conducted a beginning of LON test to verify the strut capacity with a test end anchorage. Thus, we cannot recommend substitution of the tubular strut in place of the current tested strut.

Response

Response
(active)

The ground strut shown in the attached detail is similar to ones tested with previous end anchorage designs that were evaluated under NCHRP 230 and NCHRP 350. Similar anchor struts have also been observed in use with previous proprietary end terminal designs.

While these struts may have worked in previous designs, their performance with the MGS system is unknown. Early in the development of the MGS, the foundation tubes were extended and the overall anchorage capacity was increased to accommodate higher anchor loads for MASH testing as well as the increased angle of the cable anchor used for the 31" height of the barrier. As such, the anchor capacity of the MGS end anchorage has increased over previous trailing end anchors. Thus, I cannot guarantee that the attached strut detail has sufficient structural capacity to work in the MGS downstream anchorage.

Additionally, I am not aware of any current terminal designs using that specific strut that have conducted a beginning of LON test to verify the strut capacity with a test end anchorage. Thus, we cannot recommend substitution of the tubular strut in place of the current tested strut.

Date March 20, 2017
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