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aisc lrfd punched holes

aisc lrfd punched holes

aisc lrfd punched holes

(OP)
If you have punched holes on connection, you add the diameter by 1/8" right?  Where can I find that on the manual? I cant seem to find it.

RE: aisc lrfd punched holes

It's not exactly like that.  Look at D3.2 of the 13th Ed. Spec.

RE: aisc lrfd punched holes

(OP)
No, I dont think it is in chapter D.  I am doing practice questions for PE exam.  I am going through this answer and I just want to know where to find it in the manual.

RE: aisc lrfd punched holes

D3.2 in my manual, too.  Second paragraph.

RE: aisc lrfd punched holes

CoEngineer, it's at:

D3.2, Page 16.1-27 in the 13th Ed.

Just in case you're looking at an older Manual,

B2, Page 16.1-10 in the 3rd Ed. LRFD
B2, Page 6-34 in the 2nd Ed. LRFD

LOL, and while we're at it (drumroll):

B2, Page 5-33 in the 1989 ASD

RE: aisc lrfd punched holes

It doesn't matter whether or not the hole is punched.  It matters what limit state is being checked.  For example, the extra 1/16 applies for checking shear or tension rupture, but not tear-out.

RE: aisc lrfd punched holes

I just realized something interesting.  D3.2 says that the width of a bolt hole shall be taken as 1/16 in greater than the nominal dimension of the hole.  On page 16.1-105 (Table J3.3) says taht the nominal dimension of the hole is 1/16" greater than the nominal size of the bolt (for a standard hole).
That being the case, the bolt hole should be taken as 1/8" greater than the nominal bolt diameter.

RE: aisc lrfd punched holes

Article 2.7 of the Guide to Design Criteria for Bolted and Riveted Joints reads:

"One of the critical details in a bolted or riveted structure is the fastener hole.  Punching the holes causes strain aging and work hardening of the material around the hole."

and

"To eliminate these points of potential crack initiation, holes should be either drilled or subpunced and then reamed in order to eliminate small surface cracks and work hardened material if brittle fracture is possible under service conditions."

Under division II of AASHTO's Standard Specifications, Article 11.4.8.1 limits the thickness of material that can be punched.

RE: aisc lrfd punched holes

(OP)
So if it was punched you add 1/8?  If it was drilled, you add 1/16?  Is that it?  Yeah, 271828, you are right.. i got the 3rd edition.

RE: aisc lrfd punched holes

COEngineer, no, in AISC-land, you add 1/16 to the nominal hole dimension regardless of whether it's punched or drilled.  This only applies to tension rupture and shear rupture limit states, not tear-out.

For example, if you have a standard hole, when checking tension rupture, shear rupture, or block shear, you'd use the bolt diamter + 1/8.

If you have an oversided hole, you'd have the bolt diamter + 1/8 + 1/16.

RE: aisc lrfd punched holes

oops, meant "diamEter," LOL.  My 2 month old started crying when I typed that--and the sun was in my eyes!

RE: aisc lrfd punched holes

That's not how I read it.  Section D3.2 says to add 1/16" to the dia. of the hole, no matter how it is fabricated.

My old college textbook (McCormack, 2nd Ed.) says that the 1/16" is to account for the damage to the holes during the punching process.  McCormack goes on to say that it is unnecessary to add/subtract the 1/16" for drilled holes.

The AISC code has apparently decided to not differentiate between the two methods, and to be conservative for drilled holes.

RE: aisc lrfd punched holes

My above post was meant to respond to COEngineer, not 271828.

RE: aisc lrfd punched holes

That's cool, jmiec.

I would guess that AISC makes no distinction because EOR types don't know what fabricator will be used, etc., so he might not know if it will be drilled or punched.  Those limit states don't control very often, so the extra 1/16 doesn't hurt much.

I think bridge folks might be closer to the process so might know more about what'll be done, but I could be wrong, not being a bridge guy.

For AISC, the part that screws everybody up is how the 1/16 only applies to some limit states.  Tear-out does sometimes control for close bolt spacing, so I guess they decided to not further simplify the situation by using the extra 1/16 there too.  Then again, I'm just guessing.

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