Shear Tab - Long Slotted Bolt Eccentricity
Shear Tab - Long Slotted Bolt Eccentricity
(OP)
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://fi les.engine ering.com/ getfile.as px?folder= 18d451a1-1 e74-46a0-b c1b-2d1ed6 e15962& ;file=Desi gn_of_Sing le_Plate_S hear_Conne ctions.pdf
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://fi






RE: Shear Tab - Long Slotted Bolt Eccentricity
Please provide a little more information. What is the support? Skewed or square framing?
http://www.FerrellEngineering.com
RE: Shear Tab - Long Slotted Bolt Eccentricity
http://www.FerrellEngineering.com
RE: Shear Tab - Long Slotted Bolt Eccentricity
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?
RE: Shear Tab - Long Slotted Bolt Eccentricity
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
RE: Shear Tab - Long Slotted Bolt Eccentricity
I would greatly appreciate that design procedure, and certainly I can wait until Tuesday. Thank you very much!
KZ
RE: Shear Tab - Long Slotted Bolt Eccentricity
Sorry I mis-spoke earlier. Bearing bolts are allowed in the connection.
Let me know if you have any questions.
http://www.FerrellEngineering.com
RE: Shear Tab - Long Slotted Bolt Eccentricity
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.
RE: Shear Tab - Long Slotted Bolt Eccentricity
Make sure you are considering eccentricity to the extreme length of the slot, not the center.
http://www.FerrellEngineering.com
RE: Shear Tab - Long Slotted Bolt Eccentricity
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.
RE: Shear Tab - Long Slotted Bolt Eccentricity
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
RE: Shear Tab - Long Slotted Bolt Eccentricity
(Please note there is no antagonism here; I'm just tying to understand the logic behind all the different shear tab variations.)
RE: Shear Tab - Long Slotted Bolt Eccentricity
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.
RE: Shear Tab - Long Slotted Bolt Eccentricity
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
RE: Shear Tab - Long Slotted Bolt Eccentricity