Shear Tab - Long Slotted Bolt Eccentricity 1

[KZSteel]

I'm checking the connections on a steel building, and the steel fabricator has specified long slots on a certain shear tab connection.

AISC Manual of Steel Construction has this to say:
"For STD hole, eccentricity can be ignored when the number of bolts, n, is less than or equal to 9. For Connections with 10 to 12 bolts, use e=n-4 and a 1.25 multiplier on the calculated eccentricity coefficient C. For SSL holes, eccentricity can be ignored up to n=12."

CISC Handbook of Steel Construction references Astaneh's 1989 Engineering Journal "Design of single plate shear connections" which says:
"ASTM A326 and A490 bolts may be used. Fully tightened as well as snug tight bolts are permitted. The procedure is not applicable to oversized or long slotted bolt holes."

How then does one go about calculating the resistance of a long slotted shear tab connection?

I have found a paper by M Thomas Ferrel that includes a figure with exactly my scenario (figure 4-5) and even references an apparent "Chapter 5" But I beleive these figures were taken from a different text, and no reference has been provided. I have attached the paper.

Can someone point me in the right direction?

Astaneh:

http://files.engineering.com/getfil...=Design_of_Single_Plate_Shear_Connections.pdf

 

[connectegr]

I will try to do justice to my father's paper. What is your condition? Shear only? Typically long-slot single plates are for skewed embed connections, where tolerances can be an erection problem. The connection does not fall in the "standard" shear plate design criteria. Eccentricity must be considered to the extreme position allowed by the slot and slip critical bolts are required.

Please provide a little more information. What is the support? Skewed or square framing?

http://www.FerrellEngineering.com

 

[connectegr]

The text referred to in my father's paper was a design guide. We developed a single plate design guide at the request AISC. But as it was completed and presented at the NASCC conference new research was commissioned on standard shear tabs. This resulted in the 13th Ed method for shear tabs. The design guide also had procedures for extended and other special single plate connections. We incorporated several studies from Europe and Australia. We use the information internally, but the draft of the design guide is on my bookshelf.

http://www.FerrellEngineering.com

 

[KZSteel]

Thank you for the prompt reply, and I apologize for misspelling your family name in my original post.

My connection is indeed an embed connection, and in the various connections I must check the resistance of, I have both skewed and square framing.

The supports are shear only.

That's too bad, the 13th ed of AISC manual doesn't give procedures for long-slotted.

So you are saying that slip critical bolts must be specified and use eccentric bolt group coefficients for the extreme end of the slot?

 

[connectegr]

KZSteel
If you can wait till Tuesday, I will send the procedure as described in the paper.

Also note, that single plates do not apply only shear at the embed. The embed must be designed for shear and moment, due to the lack of flexibility of the connection.

http://www.FerrellEngineering.com

 

[KZSteel]

connectegr,

I would greatly appreciate that design procedure, and certainly I can wait until Tuesday. Thank you very much!

KZ

 

[connectegr]

SEE ATTACHED
Sorry I mis-spoke earlier. Bearing bolts are allowed in the connection.

Let me know if you have any questions.

http://www.FerrellEngineering.com

 

[KZSteel]

connectegr,

Thank you for the file, it helps alot, but I am wondering why eccentricity is factor for the bolts. AISC 13th Ed Manual states that eccentricity can be ignored in standard and short slotted holes, and my connection falls under all other connditions for this, but instead of direct shear for short slotted or standard, I am forced to use a coefficient of 0.88? (for a bolt spacing of 3in, e-bolt of 3in, n=2 bolts in my connection's case) If short slots are used, C=n=2. Seems like a pretty big difference just by making the slots a little longer.

 

[connectegr]

Short slots and standard holes, where the only conditions tested to achieve the new method. Other configurations, including long-slots are considered "extended shear plate" connections.

Make sure you are considering eccentricity to the extreme length of the slot, not the center.

http://www.FerrellEngineering.com

 

[nutte]

Connectegr,

Thank you for posting the pages from the draft of the design procedure. Can you elaborate how bearing bolts can be used in long slotted holes on shear tabs to embed plates? The bolt group sees a moment. With slotted holes, the extreme bolt won't have anything to bear up against. It would seem that slip critical bolts would be necessary here, too.

 

[connectegr]

Research done at the University of Oklahoma by Duggal and Wallace.

a. frictional forces between the plate and beam web, due to initial tensioning of bolts

b. frictional forces between plate and web, due to lateral swelling of the slotted plate

c. "bolt plowing"

d. force required to overcome increased lateral swelling friction which increases due to bolt plowing.

http://www.FerrellEngineering.com

 

[nutte]

It is my understanding that if we use SSL holes in an extended shear tab, we must use slip critical bolts. If the items you list above apply to LSL holes, wouldn't they also apply to SSL holes, allowing us to use bearing bolts there, too?

(Please note there is no antagonism here; I'm just tying to understand the logic behind all the different shear tab variations.)

 

[a2mfk]

Connectegr,
Thanks for that document too, added it to my library. Checked out your website, some nice projects. BTW, Ford Amphitheater is in Tampa not Orlando... Was that wall only for acoustics or for some type of screen/privacy wall for during concerts? Saw that thing being built and always wondered all of its purposes, the geometry on some of those connections must have been a nightmare... Like a Gehry-designed wall.

 

[connectegr]

nutte,
There has been limited research on extended plates or connections with multiple columns. We use bearing bolts and SSH for extended plates with a single column of bolts. But, standard holes or slip critical bolts with multiple columns. There is a point where the resultant horizontal forces exceed the horizontal resistance factors listed above.

a2mfk
Thanks. We like working on the weird stuff, and Frank Gehry rarely disappoints. We worked on a couple of his designs. I heard several reasons for the amphitheater. Highway noise, neighborhood noise concerns, etc. The members were fairly small, but the geometry and load combinations were a mess.

http://www.FerrellEngineering.com

 

[nutte]

Good deal. Thanks for the responses.