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Questions about the MGS Trailing End Terminal

Question
State	WY
Description Text	We have a couple of questions regarding the MGS Trailing End Terminal as reported in TRP-03-279-13: 1. On pages 155 and 167, a single span rail (6’-3”), part a3 is incorporated into the design. Why? Is this necessary for the terminal to work properly? 2. On sheet 165, the cable anchor is shown to have an overall length of 80 inches. The old metric standard barrier guide calls out 2000 mm (78 ¾”). The old, old guide calls out 78 inches. Obviously some rounding was applied when it was made metric. This cable is not shown in the current on-line guide. Should this figure on page 165 really show 78 inches since it references a part number from the standard barrier guide, or does it require a special cable?

Question

State

Description Text

We have a couple of questions regarding the MGS Trailing End
Terminal as reported in TRP-03-279-13:

1. On pages 155 and
167, a single span rail (6’-3”), part a3 is incorporated into the design. Why? Is
this necessary for the terminal to work properly?

2. On sheet 165, the cable anchor is shown to have an
overall length of 80 inches. The old
metric standard barrier guide calls out 2000 mm (78 ¾”). The old, old guide calls out 78 inches. Obviously
some rounding was applied when it was made metric. This cable is not shown in
the current on-line guide. Should this
figure on page 165 really show 78 inches since it references a part number from
the standard barrier guide, or does it require a special cable?

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Road Closure Gates
Thrie Beam Guardrails

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Date July 3, 2014
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Attachment MGS Trailing Terminal.docx

Response
Response (active)	The single 6'-3" rail segment was used for testing purposes to set the overall system length at 175'. For real world installations, this system length is not required and would not necessitate the extra rail segment. It is important to maintain the splice locations at the mid-span between the posts to maintain the benefits of the MGS system. With respect to the anchor cable length, we believe that either length is acceptable. The hardware guide specifies the 78.75” long anchor cable. We have used that length in these types of end anchorage for many tests. In more recent years, our guardrail part supplier has begun supplying the 80” long version, so we have been testing with that. One related item to note deals with the location of the cable bracket on the guardrail. According to the hardware guide, the cable bracket should be located such that the first bolt for the bracket is 1250 mm or 49.25” from the center of post no. 1. The downstream anchor report you mentioned above shows this distance as 47.625”. Going back through our records, it appears that this anchor bracket has varied slightly in location over time. However, we would recommend that the 49.25” location be used in order to be consistent with the hardware guide and to minimize the angle of the cable as it approaches post no. 1.

Response

Response
(active)

The single 6'-3" rail segment was used for testing purposes to set the overall system length at 175'. For real world installations, this system length is not required and would not necessitate the extra rail segment. It is important to maintain the splice locations at the mid-span between the posts to maintain the benefits of the MGS system.

With respect to the anchor cable length, we believe that either length is acceptable. The hardware guide specifies the 78.75” long anchor cable. We have used that length in these types of end anchorage for many tests. In more recent years, our guardrail part supplier has begun supplying the 80” long version, so we have been testing with that.

One related item to note deals with the location of the cable bracket on the guardrail. According to the hardware guide, the cable bracket should be located such that the first bolt for the bracket is 1250 mm or 49.25” from the center of post no. 1. The downstream anchor report you mentioned above shows this distance as 47.625”. Going back through our records, it appears that this anchor bracket has varied slightly in location over time. However, we would recommend that the 49.25” location be used in order to be consistent with the hardware guide and to minimize the angle of the cable as it approaches post no. 1.

Date July 10, 2014
Previous Views (149) Favorites (0)