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Using a Blockout with MGS Bridge Rail

Question
State IA
Description Text In the MGS Bridge Rail report, it is suggested that a 4-inch deep blockout could be used to minimize the chance of snowplow damage to the deck-mounted through bolts.  However, it goes on to say that "additional analysis or testing is required before alternate rail mounting details can be recommended."  Has this analysis been completed, or is MwRSF in a position to suggest an alternate mounting method at this time?  If not, would it be possible to utilize the existing mounting details with a blockout, except with a longer bolt?
Keywords
  • Bridge Rails
Other Keywords none
Date December 2, 2013


Response
Response

We have not had the opportunity to investigate the use of blockouts with the MGS bridge rail. The current connection design is based on a connection used for weak post W-beam guardrail without blockouts and has not been evaluated with blockouts.

The concern with the using a blockout and the existing bolt and washer connection is that the small bolt in the design may not be sufficient to support the dead weight or that the disengagement may change. Thus, we believed that further study would be required to investigate the use of spacer blocks prior to introducing them into the design.

TTI has tested an alternative post connection for the MGS bridge rail that uses a deck mounted post. This attachment may not have the same degree of interference with snow plows. However, the design does intrude onto the deck more. See attached.

Date December 10, 2013
Attachment T631-8inchDeckAssemblyOpt10.PDF


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