Logged in as: Public User

MGS BLOCK ROTATION

Question
State
Description Text When you tested the MGS system, you added a ¼” hole at the top of the post to drive a nail into the block to keep the block from rotating.  From a manufacturing standpoint, this hole is a pain in the behind.  This hole cannot be punched and has to be drilled in a separate operation.

I would like to propose a couple of options to this hole. 

1. We drill two holes in the post for placing the rail bolt.  One on each side of the web.  Could this hole be used?
2. Could a nail be placed into the top of the block and then bent over the top of the post?
3. Could a nail be placed into the side of the block and then bent over the side of the post?
4. If routered blocks are used, is a nail required at all?

We would like to come to a better solution than drilling the ¼” hole.

Thanks
Keywords
  • Guardrail
Other Keywords none
Date May 8, 2013


Response
Response

Several years ago, the Iowa DOT installed 1 run of MGS in the north east corner of the state. After a major snow storm with heavy snow, a plow cleared the traveled lanes and move substantial wet snow off of the road, much of which struck the routed blockouts. A short-term fix was to use four nails in the back corners, which were then bent over the post flange to prevent rotation. Here is what we wrote in 2008:

 

We agree that this blockout rotation would appear to be caused by snow removal operations. To resolve your blockout issue and eliminate the requirement to field drill holes in the steel flanges, we recommend that you place four (4) nails in the top and bottom corners on both sides and bend the nails over the flanges. The four nails should provide adequate resistance to block rotation, even under snow removal operations. For this solution, you could use 16-d nails, but it may be preferred to use 20-d nails with this alternative. Please note that it would not be necessary to have the post webs on the back of the blockout using this option.”

 

Comments to your email are contained below in red.

 

_______________________________________________________

 

 

Ron

 

When you tested the MGS system, you added a ¼” hole at the top of the post to drive a nail into the block to keep the block from rotating.  From a manufacturing standpoint, this hole is a pain in the behind.  This hole cannot be punched and has to be drilled in a separate operation.

 

I would like to propose a couple of options to this hole. 

 

1.        We drill two holes in the post for placing the rail bolt.  One on each side of the web. Could this hole be used?

**This option would not provide much rotational resistance due to its location in close proximity to the bolt.

2.       Could a nail be placed into the top of the block and then bent over the top of the post?

**I do not like the top bent nail option very much as block could rotate under it.

3.       Could a nail be placed into the side of the block and then bent over the side of the post?

**A minimum of two bent nails would be my recommendation for this concept when nail location placed at upper sides.

4.       If routered blocks are used, is a nail required at all?

**We do not think that nails are required if block is routed. However, we have seen a special case where significant, wet snow was plowed and caused partial rupture of routed block tabs, as noted above. In those scenarios, we had Iowa use four bent nails.

 

We would like to come to a better solution than drilling the ¼” hole.

Date May 28, 2013


Contact Us:
130 Whittier Research Center
2200 Vine Street
Lincoln, NE 68583-0853
(402) 472-0965
Email: mwrsf@unl.edu
Disclaimer:
The information contained on the Midwest Roadside Safety Facility (MwRSF) website is subject to change without prior notice. The University of Nebraska and the MwRSF is not responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with the use or misuse of or reliance upon any such content, goods, or services available on this site.