F1554 Anchor Bolt: how to design for tension + shear?
F1554 Anchor Bolt: how to design for tension + shear?
(OP)
I am having trouble finding how to design an F1554 anchor bolt, about 18" long, for tension and shear.
There is plenty of info for A325 and A490 bolts in Section J3.7 of the LRFD, but nothing for F1554...and according to the AISC (April 2002 MSC Steel Quiz) F1554 is the appropriate grade for anchor bolts > 9.5" long...NOT A325 or A490.
Can anyone help?
There is plenty of info for A325 and A490 bolts in Section J3.7 of the LRFD, but nothing for F1554...and according to the AISC (April 2002 MSC Steel Quiz) F1554 is the appropriate grade for anchor bolts > 9.5" long...NOT A325 or A490.
Can anyone help?






RE: F1554 Anchor Bolt: how to design for tension + shear?
I don't have the 3rd edition LRFD, but J3.7 in the new 13th edition is also combined tension and shear in bolts. I wouldn't have a problem using the same formulas for anchor rods (F1554) as for bolts (A325 or A490).
As a simple conservative check, I might use fv/phiFv + ft/phiFt <1.0.
The equations in J3.7 allown full strength of shear or tension if the smaller of the two is less than 20% of the available strength.
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
Table 2-5 on page 2-41 in the 13th edition (I am sure there is a similar table in the 3rd edition LRFD) gives the ultimate tensile stress for ASTM F1554 as 58-80 ksi. Using this information in conjuction with Table J3.2, I would use phiFt=0.75Fu*(Area of rod)=43.5*(area of rod); and
phiFv=0.40Fu*(Area of rod)=23.2*(area of rod).
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
Anchor rods (yes correct terminology is rods) should be designed for both steel and concrete limit states.
AISC provides methods for the steel component, and ACI provides methods for both the steel component and the concrete component. The steel design component of ACI and AISC differ from each other in methodology but end up with approximately the same answers.
As an example take a 3/4" diameter, F1554 Gr36 rod in tension:
AISC Method: As Structural EIT described, per J9 (referencing the 13th ed manual) the anchor rods should be designed as threaded parts per table J3.2. Per table J3.2, for threaded rods Fnt = 0.75Fu. Per Table 2-5, Fu (min) = 58ksi. Per equation J3-1, Rn = FnAb where Ab is the full cross-sectional area of the bolt. So for LRFD, PhiRn = (Phi=0.75)*(Fnt=0.75*Fu=58)*(Ab=Pi(0.75^2)/4 = 14.4k.
ACI Method: Per Appendix D, the strength of a single anchor in tension, Nsa = Ase*Fu. Phi factors differ depending on if the anchor material is ductile or not, with ductile being defined as having a tensile elongation of 14% and reduction in area of at least 30% per the material ASTM standard. From the ASTM standard for F1554, Gr36 qualifies as ductile and gets a phi factor of 0.75. Ase is the EFFECTIVE cross sectional area of the rod (see commentary RD.5.1.2 in ACI Appendix D). It can be calculated per the commentary equation but is also available in Table 7-18 of the AISC 13th edition manual. For this bolt, Ase = 0.334. So the final tensile strength = (Phi=0.75)*(Ase = 0.334)*(Fu = 58ksi) = 14.53k.
So you are looking at 14.4k with the AISC method vs. 14.53k with the ACI method.
RE: F1554 Anchor Bolt: how to design for tension + shear?
Am I wrong in saying that the ACI appendix will only give you shear and tension values (and interactions) for the concrete breakout strengths, and not for the anchor rod?
Nutte-
The new base plate design guide #1 follows the same formula EXACTLY for tension and shear interaction in anchor rods as for bolts (as shown in equation J3-3a) in the 13th Edition steel manual. See AISC Design Guide #1 page 43 as a reference.
Hippo-
I would follow the design guide, but if you don't have access to it the formula for tension and shear interaction are identical as in the 13th edition on page 16.1-109 (Eq. J3-3a). I would get the Fv and Ft capacities as described above. Those capacities that I mentioned earlier are for loads, not stresses. For stresses, just use the phi=0.75 for tension and 0.4 for shear and a nominal stress of 58 ksi (unless you are specing a higher strength).
RE: F1554 Anchor Bolt: how to design for tension + shear?
You're right about the AISC checks in the Design Guide 1. But when you go through the ACI appendix procedure, you'll end up checking them there as well.
A note of caution about using the AISC equations for anchor rods: You usually have super-oversized holes at base plates, so the plate might not engage the anchor rod in shear. You can resist shear through a shear lug, friction under the base plate, embedding the base plate in concrete, etc. You also often have a grout cushion between the concrete support and bottom of base plate, so if you are counting on the anchor rods to resist shear, you'll induce bending in the anchor rod. All of these issues are absent in steel-to-steel bolted connections, which the AISC equations are primarily intended for.
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
Good Luck.
RE: F1554 Anchor Bolt: how to design for tension + shear?
I hear from my spies that this appendix is a "work in progress" and that "big" changes are on the way. However, I would not wait for it soon.
It is way too tedious to use and I have reverted back to my old way of doing anchors.
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
What irks me the most is that our anchor rods are always surrounded by rebar. This procedure neglects that, yet it's supposed to be the "best" method around. I hate it. If it's a "work in progress," they should have left it on the drawing board. It's the most backward procedure I've come across.
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
The bending moments are determined using a beam model fixed at the top of the concrete, and freee to displace but not rotate at the bottom of the leveling nut. For bending stresses, I use the root diameter of the thread, in lieu of the tensile stress diameter.
Finally, AASHTO recommends that the base plate be equal to or greater than the diameter of the bolts. Thinner base plates contribute dramatically to the bending moments in the anchor bolts.
RE: F1554 Anchor Bolt: how to design for tension + shear?
RE: F1554 Anchor Bolt: how to design for tension + shear?
larryzim-
What you say makes sense, but where exactly does it say that appendix D is for unreinforced concrete? I can't find that anywhere.
All-
D.2.2 says that this applies to cast-in anchors AND post-installed anchors. Then it also says that specialty inserts, adhesive and grouted anchors are not included. What kind of post-installed anchor is NOT a specialty insert, or and adhesive or grouted anchor?
This statement also leads me to the conclusion that hilti and powers values are to be used from their catalogs and NOT to investigate their capacities via appendix D.
Any comments?
RE: F1554 Anchor Bolt: how to design for tension + shear?
Dik