Anybody is suggesting me use double nuts on bolted connections for primary frame of buildings -one under the head of the bolt and one under the nut-
Is there any note or recommendation on the AISC codes that prohibits or suggests these can't be done?
Thanks.
From my exceptions:
INSTALLATION OF ‘JAM’ NUTS (NOT RECOMMENDED):
(REFER TO: THE INNER JAM NUT SHALL HAVE A THICKNESS OF NOT MORE THAN 75% OF THE OUTER NUT;
THE INNER NUT SHALL BE INSTALLED FIRST AND SNUGGED TO 50% OF THE TORQUE VALUE;
THE OUTER JAM NUT SHOULD BE INSTALLED SNUG TO THE INNER JAM NUT;
THE INNER NUT SHOULD BE RESTRAINED TO KEEP FROM ROTATING AND THE OUTER JAM NUT SHOULD BE FULLY TORQUED TO IT; AND
WRECK THE THREADS ABOVE THE NUT.
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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
They must mean a double nut on the thread side, right? Or washer one side nut on the other. Putting a nut on the head side of a bolt is something my wife might do if she was the steel installer.
I would like to see someone get a nut all the way to the head of an A325 bolt:
Surely the question is actually about washers?
If so, it would be acceptable to use two as described, though generally not required.
dik said:
From my exceptions:
INSTALLATION OF ‘JAM’ NUTS (NOT RECOMMENDED):
(REFER TO: THE INNER JAM NUT SHALL HAVE A THICKNESS OF NOT MORE THAN 75% OF THE OUTER NUT;
THE INNER NUT SHALL BE INSTALLED FIRST AND SNUGGED TO 50% OF THE TORQUE VALUE;
THE OUTER JAM NUT SHOULD BE INSTALLED SNUG TO THE INNER JAM NUT;
THE INNER NUT SHOULD BE RESTRAINED TO KEEP FROM ROTATING AND THE OUTER JAM NUT SHOULD BE FULLY TORQUED TO IT; AND
WRECK THE THREADS ABOVE THE NUT.
This is critical information. From what I've read, the common approach of two equal thickness nuts doesn't help.
Concur... and not recommended. I design connections for metal fabricators and often come across 'jam nuts'. That's why my exceptions have these notes.
I was a little puzzled about the original question. A nut under the head does absolutely nothing.
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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
Oh sorry. Yes I was talking about washers.
Oups.
The main idea is for bolted connections on cold formed material is there any increase in capacity for using a washer on head additionally to the washer that goes with the nut?
RCSC Section 6 tells you everything you need to know about washers. There's no impact on capacity, but they are definitely required under the head in certain circumstances.