Need some immediate help on coupling nuts

[bnickeson]

So long story short, I have a detail where an A325 bolt is threaded into one side of a coupling nut and the opposite side is rebar embedded in a wall. I originally specified a specific Lenton coupler that the fabricator apparently didn't use. What was supplied was a "Grade 2" coupler which in my research is equivalent to A563 Grade A. Looking on Portland Bolt's website, they have a compatibility chart for the grade of coupler to use for each rod/bolt type of attached member. https://www.portlandbolt.com/technical/nut-compatibility-chart/

The applied load from the bolt to the coupler is only around 60% of the yield strength of the rebar, but I would like the coupler to be properly specified to develop more strength than the yield of the rebar. The portland bolt site doesn't have rebar anywhere in there, but it does have A325 bolts and it does have Grade 55 rods. The A325 coupler grade is recommended to be Type "C" which is a higher grade than the Type "A" that was provided. However, F1554 Grade 55 is shown to have a recommended nut type of Grade "A". Should I assume that the provided Type "A" nuts in my case can develop the yield strength of the attached rebar, or at least very close to it?

Thanks in advance.

 

[Phil1934]

width of coupler nuts may be less than regular nuts so may be weaker

 

[jjl317]

I think the information from Portland is on the "standard" nuts, not couplers, and I don't know that assuming that they have the same cross-section is a good idea.

In my mind, I would expect that you would need to do some analysis (thread pullout of the various components, overall tension on the coupler, etc. ) based on the real geometry and material properties to confirm - not sure you are going to find a chart that addresses this.

 

[jjl317]

Attached is an article that may be of assistance

https://www.aisc.org/globalassets/modern-steel/archives/2016/09/steelwise_2.pdf

 

[bnickeson]

I think the information from Portland is on the "standard" nuts, not couplers, and I don't know that assuming that they have the same cross-section is a good idea.

In my mind, I would expect that you would need to do some analysis (thread pullout of the various components, overall tension on the coupler, etc. ) based on the real geometry and material properties to confirm - not sure you are going to find a chart that addresses this.

It's absolutely wild to me that something designed to couple two rods together does not have any published load information whatsoever. https://www.portlandbolt.com/technical/faqs/coupling-nut-load-ratings/

Also, I found this table https://torqbolt.com/asme-b18-2-2-hex-coupling-nuts-dimensions-standards-specifications which gives smaller dimensions than standard hex nuts. So this is a bit of a mess.

 

[lexpatrie]

Why aren't you just telling them to use what was specified?

 

[bnickeson]

Because I found out about this Friday morning and they're pouring the concrete walls starting Monday. The specified couplers would have taken weeks to source at this point apparently which would have amounted to tens of thousands in delays. I already read the fabricator the riot act.

 

[lexpatrie]

That sounds like their bad act, not yours.