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AGT Thrie Beam End Shoe Connection

Question
State WY
Description Text

Our field personnel came up with this question.  I think he is pointing out that the standard splice bolts have a shoulder which typically goes into the splice slots.  With the washer, the bolt head would sit above the washer, unless the washers are cut with a slotted hole.  How is this delt with?  Don Gripne was the one who alerted me to the practice of using the washers when the thrie beam shoe stacks on the outside of the rail, unfortunately he did not elaborate on the details.  Could you give me some guidance here? Any help would be appreciated.  Again we are talking about the thrie beam section of MGS and how it connects to the end shoe.



 



Quick question about the thrie beam shoe on the standard plans sheet 6 of 16.  There's a note that says that washers are to be used between the bolt heads and the end of the shoe when the end shoe is placed outside of the thrie beam.  Upon installation, the carriage bolts will not tighten if the washer is used in that way because the washer blocks the carriage bolt from getting a grip.  Do we want to use the washer that way anyway, even though it doesn't let the bolt get tight?  Thanks for your input. 



MASH
TL-3

Approach Guardrail Transitions (AGTs)


Fasteners

Date September 27, 2023
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We have also run into this issue where the thrie beam end shoe splices with the thrie beam rail. The thrie beam end shoe is often the bottom of the plies of rail being connected to make the lap splices match with the traffic flow (i.e. upstream rail section on top).

Because the thrie beam end shoes can have oversized slots to facilitate assembly, we have placed washers on the underside or nut side of that connection to prevent the nuts from being pulled through.

We have not had an instance of having to put washers on the upper portion of that connection because that would be an incorrect splicing operation for oncoming traffic. As noted below, this would also not be possible due to the shoulder on the splice bolts interfering with the washer.

If you are looking at trailing ends, this issue might arise. In that case, the best option may be to install a custom, notched washer to accommodate the shoulder on the splice bolts.

Let me know if that helps.


Date September 28, 2023
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I forgot you guys probably don’t run any downstream tests, and yes, that is where the situation would occur. Do you think we could get away with hex head bolts?

 


Date September 29, 2023
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I am not sure that hex head bolts would work. I don’t believe that they would be any different in size than the nuts or larger the head of the splice bolts. Thus, it may not help with pulling through the slots.

 

If you use them with washers, that would help with pull through. The only concern would be snag on the bolt heads. I don’t have any directly comparable data to suggest what effect that may be. It should not be very significant as the splice bolts are tucked along the sides of the rail valley and not on the top of the rail humps. Thus, the snag may be minimal. We have seen snag on hex bolt heads where the flat end of the shoe connects to the parapet, but it was not sufficient to cause an issue. So hex bolts may be an option.


Date September 30, 2023
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