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MGS in median

Question
State	OH
Description Text	Good Morning, We currently have a strong-post median barrier with rub rail (SGM06a - ODOT Type 5MR) installed in the median of Interstate 71 (see attached cross section). The district is adding 3" of asphalt to the pavement up to the face of the barrier. 1) Is there a height tolerance for this barrier? 2) Can this system be raised by moving the blockouts and would the backside rub rail also be raised? 3) Would two sided MGS be an acceptable option with a 6:1 backside slope on a 30' median cross section? We had a similar issue in 2006. http://mwrsf-qa.unl.edu/view.php?id=459 Thanks!

Question

State

Description Text

Good Morning,

We currently have a strong-post median barrier with rub rail (SGM06a - ODOT Type 5MR) installed in the median of Interstate 71 (see attached cross section). The district is adding 3" of asphalt to the pavement up to the face of the barrier.

1) Is there a height tolerance for this barrier?

2) Can this system be raised by moving the blockouts and would the backside rub rail also be raised?

3) Would two sided MGS be an acceptable option with a 6:1 backside slope on a 30' median cross section?

We had a similar issue in 2006.

http://mwrsf-qa.unl.edu/view.php?id=459

Thanks!

System Performance Evaluation

System Types
Road Closure Gates
Thrie Beam Guardrails

Applications

System Features

Date August 3, 2018
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Attachment GR_5MR.pdf Attachment Type 5MR Typical.pdf Attachment IR.71 photo.JPG

Response
Response (active)	I have several comments with regards to the median guardrail in question. First, you noted that we had discussed this system previously in 2006 - http://mwrsf-qa.unl.edu/view.php?id=459 We had a follow on discussion in 2013. In it we noted some concerns regarding the use of rub rail and placement of the system adjacent to 6:1 slopes. You should review that and see if you have any questions regarding those previous comments related to this system. https://mwrsf-qa.unl.edu/view.php?id=713 I have a few other comments as well. 1. We would not recommend using heights below 31" for the MGS median barrier or other doubled sided median W-beam systems at this time. TTI tested the G4(1S) median barrier system in NCHRP 157 to MASH TL-3. In those tests, the pickup truck vaulted the barrier when installed at the 27 in. mounting height. It has been successfully tested to MASH TL-3 at the 31in. height. 2. The system height could potentially be raised by moving the blockouts up. This has been shown to be acceptable for roadside installations, so we would expect similar performance for the median version. 3. I noted in the detail that the posts for the system were installed in 3-in. of asphalt. We would have concerns that installation of the post in asphalt could degrade performance due to limited post rotation if proper leave outs were not employed. Let me know if that addresses you questions or if you have further items you wish to discuss. Thanks

Response

Response
(active)

I have several comments with regards to the median guardrail in question.

First, you noted that we had discussed this system previously in 2006 - http://mwrsf-qa.unl.edu/view.php?id=459

We had a follow on discussion in 2013. In it we noted some concerns regarding the use of rub rail and placement of the system adjacent to 6:1 slopes. You should review that and see if you have any questions regarding those previous comments related to this system.

https://mwrsf-qa.unl.edu/view.php?id=713

I have a few other comments as well.

1. We would not recommend using heights below 31" for the MGS median barrier or other doubled sided median W-beam systems at this time. TTI tested the G4(1S) median barrier system in NCHRP 157 to MASH TL-3. In those tests, the pickup truck vaulted the barrier when installed at the 27 in. mounting height. It has been successfully tested to MASH TL-3 at the 31in. height.

2. The system height could potentially be raised by moving the blockouts up. This has been shown to be acceptable for roadside installations, so we would expect similar performance for the median version.

3. I noted in the detail that the posts for the system were installed in 3-in. of asphalt. We would have concerns that installation of the post in asphalt could degrade performance due to limited post rotation if proper leave outs were not employed.

Let me know if that addresses you questions or if you have further items you wish to discuss.

Thanks

Date August 15, 2018
Previous Views (218) Favorites (0)