Hole Size (Slip Critical Connection)
Hole Size (Slip Critical Connection)
(OP)
Folks,
I recently got a call from a steel fabricator regarding some oversized holes we had specified.
The bolts in question are 1" diameter A490 SC bolts in oversized holes through 1.25" thick plate. The fab said that he wanted to use bigger holes than 1.25" because of his punching machine.
The code has maximum hole dimensions published in table J3.3, but what are the problems with the use of say a 1-5/16" hole as opposed to a 1.25" hole for a SC connection with 1" bolts in OVS holes.
He is proposing to use 1-1/8" bolts instead of 1" bolts to work with his shops limitations. Has anyone else run into such a problem before?
I recently got a call from a steel fabricator regarding some oversized holes we had specified.
The bolts in question are 1" diameter A490 SC bolts in oversized holes through 1.25" thick plate. The fab said that he wanted to use bigger holes than 1.25" because of his punching machine.
The code has maximum hole dimensions published in table J3.3, but what are the problems with the use of say a 1-5/16" hole as opposed to a 1.25" hole for a SC connection with 1" bolts in OVS holes.
He is proposing to use 1-1/8" bolts instead of 1" bolts to work with his shops limitations. Has anyone else run into such a problem before?






RE: Hole Size (Slip Critical Connection)
http://www.FerrellEngineering.com
RE: Hole Size (Slip Critical Connection)
http://www.FerrellEngineering.com
RE: Hole Size (Slip Critical Connection)
If the thickness of the material is large compared to the hole size (like burning a 1" hole in a 1" plate) the hole can have a slight taper to it.
I agree with ConnectEgr about accepting a smaller hole.
A larger hole will reduce the contact area of the faying surfaces. Tell the Fabricator to go buy a 1 1/4" slugger bit and drill the holes the right size. That will be cheaper than buying "x" amount of 1 1/8" bolts if there is any significant amount at all.
Read sections 3.3.3 & 3.3.4 of RCSC about short slotted & long slotted holes with slip-critical joints. This may shine a little light.
I believe the same comments are made in AISC.
RE: Hole Size (Slip Critical Connection)
RE: Hole Size (Slip Critical Connection)
http://www.FerrellEngineering.com
RE: Hole Size (Slip Critical Connection)
RE: Hole Size (Slip Critical Connection)
ToadJones, you have worked with more respectable fabricators than I have!
RE: Hole Size (Slip Critical Connection)
ToadJones
I work with many "respectable" fabricators. But, I find that they are rarely aware of these types of conditions and the impact they have on the engineering. I could make a mile long list of the fabricator/erector changes that may seem insignificant and may not even get an NCR or RFI for verification.
"No need to thank us, we just made all the holes bigger and used the larger bolts"
"The holes wouldn't line up, so we (burned) slots. Of course they are within AISC tolerances, under that 5" plate washer."
"We just welded it. I think that single pass fillet weld measured 1/2". Should be more than enough."
http://www.FerrellEngineering.com
RE: Hole Size (Slip Critical Connection)
Now, I'm not saying that this is acceptable. I would think that you might loose some of the normal force due to flexing of your washer... but if your washer was infinitely rigid why would the size of the hole matter? Punched vs. reamed is a different issue.... And this only pertains to SC connections.
Something similar to this was mentioned in an AISC connection seminar I went to years ago but I don't know if it pertained to oversized holes or not. Maybe you could send an email to the AISC regarding this issue and see what their response is.