Prying Action
Prying Action
(OP)
I'm working late and having a brain fart....
I have a simple connection with a beam whose top flange is bolted to the bottom flange of another beam (hanger-type).
Beams are 90 degrees to each other. The bolt gage on the lower beam is 3" and the distance between the bolts in the orthogonal direction is 2". So the bolt pattern is 3"x2".
Is the "p" distance in AISC's prying calc in this situation half of the 2"(or = 1") or could it be considered 2" since it is "the distance tributary to the bolt row". ????
I hope I am not completely embarrassed as I read the answers here![[blush] blush](https://www.tipmaster.com/images/blush.gif)
(P.S. dont blame me for the bolt pattern...its existing)
I have a simple connection with a beam whose top flange is bolted to the bottom flange of another beam (hanger-type).
Beams are 90 degrees to each other. The bolt gage on the lower beam is 3" and the distance between the bolts in the orthogonal direction is 2". So the bolt pattern is 3"x2".
Is the "p" distance in AISC's prying calc in this situation half of the 2"(or = 1") or could it be considered 2" since it is "the distance tributary to the bolt row". ????
I hope I am not completely embarrassed as I read the answers here
![[blush] blush](https://www.tipmaster.com/images/blush.gif)
(P.S. dont blame me for the bolt pattern...its existing)






RE: Prying Action
One thing that stands out to me, though, is the lack of torsional restraint at the support for the lower beam. Maybe you can add stiffeners and that kills two birds with one stone?
RE: Prying Action
I dont think I can add stiffeners, its a monorail.
what is the logic behind killing the two birds with stiffeners.
Keep in mind, I am not question you, just been working since 7:30 am...with some breaks.
RE: Prying Action
I've never dealt with a monorail, so I have no idea how much room you might have, but even if you could get partial depth stiffeners in and leave room below them that would help.
RE: Prying Action
If this were just a beam-to-beam, stiffeners would be default IMO.
Of course 2" isnt much room for that with bolts in there too.
Monorails typically have no stiffeners in this situation. There isnt much room for them at all and often times these places move trolleys and hoists from monorail to monorail as needed....hate to move one and have it hit the stiffeners!
RE: Prying Action
RE: Prying Action
Running across some weird numbers as I finish this up.
If I assume the bolts are A307, I actually get a higher allowable than if they were A325 bolts.
In designing new, this would probably never come up as one would most like choose a bolt and run with it.
Anyone ever run into this???
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Ignoring the top beam, the bottom beam has 4 bolts. I would use p equal to 1" (half the row spacing) plus the distance from the end of the beam to the bolt (assuming you're near the end of the beam). If you're not near the end of the beam, use an end distance of 6 times the bottom beam flange thickness, and add this to your 1".
RE: Prying Action
I am in the middle of the beam, as you mention.
I decided to use p=2.0"
AISC suggests using p no greater than the beam gage on the supported beam, which in this case would be 3".
P=2.0" gave me adequate results.
I am pretty confident in my numbers and, A307 bolts give a very slightly higher capacity then A325's.
RE: Prying Action
I'm curious about the A307 bolts being stronger. Feel like posting your calculation?
RE: Prying Action
I don't have the copy of the AISC manual you guys are using on Hanger-Type Connections. And, only God and AISC people who worked on this particular section of the code know the whole truth, as they see it... but my guess or thoughts on the matter are: (1.) One would normally think that the supported beam is the lighter beam in terms of flange thickness and thus the beam to check. And, if that's not the case, because of the funny bolt gages and spacings you indicate (I'm not sure I see your picture either), are you checking the critical flg. condition? Mightn't the relationships btwn. 'a' & 'b' lengths, flg. thick., and 'T' & 'Q' forces on the other beam give you a more critical condition? Which flg. is actually causing the prying? I don't know the answer to that. (2.) The reason that A307 bolts give a slightly better result than A325's might be that they relax, under prying action, a bit more than the A325's, and thus allow a slight redistribution in flg. plate moments under the bolts and at the beam web, thus a slightly improved flg. stress, or different flg. deformation. This would be buried someplace in one of the AISC multiplying or adjustment factors, or one of their equations, and would not be particularly obvious to us. Oh!, the mysteries of steel design.
RE: Prying Action
excuse the handwriting and sloppiness.
RE: Prying Action
My thoughts were the same. I was thinking (while buried over my head in jobs) that the weaker grade bolt might elongate more under the same loading....or something along those lines, and this might be relieving some of the "prying action".
In any case, this is better than the prying action I receive from my wife after coming home smelling like IPA from picking up take out.
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And A325 bolts definitely have a greater tensile strength, than A307.
http://www.FerrellEngineering.com
RE: Prying Action
what's tc ?
and why is it dependent on the allowable load of the bolt ?
RE: Prying Action
do you agree, or am I screwing something up?
RE: Prying Action
You asked "I don't understand where the bolt grade applies to the prying capacity of the flange."
Isn't the prying check for the bolt itself?
Does not the prying mechanism induce more tensile load to the bolt?
RE: Prying Action
RB, tc is the plate thickness required to fully develop the bolt tensile strength with no additional prying forces induced. A stronger bolt requires a thicker plate to fully develop the bolt's strength.
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http://www.FerrellEngineering.com
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Pretty asinine on my part.
Apologies to all for wasting your time.
RE: Prying Action
You keep throwing me curve balls and then laughing at me when I miss them. I thought you were talking about a larger difference. I'd call that round-off error too. And flg. plate bending is controlling your design, so bolt strength makes no diff. Your answer will be the same for either .75" dia. bolt.
RE: Prying Action
I dropped the ball here by simply getting tunnel vision on the bolt strength.
Quite pathetic really.
I'd like to blame it on the fact that it is an existing structure evaluation for which I have been asked to make an assumption on bolt strength that lead to my being a fool, but that would be more pathetic.
I usually check flange bending by other methods.
By the way, bolts will be replaced