As JStephen has mentioned, in ACI-318 app. D, I do not see any minimum embedment requirements. On the other hand the app. mentions a maximum diameter of the anchors and max embedment depth for which the equations in this chapter can be applied.
These are published in the first edition of the AISC Base Plate Design Guide (12d for A307 and A36; 17d for A325 and A449). These are also absent from the second edition of this same design guide, so there is probably something to that.
I believe AISC's 2nd LRFD edition (the 2-volume silver books) had a table with edge distances and embedment lengths (I don't have that edition with me right now).
The 3rd LRFD Edition refers to IBC and ASCE 7 (page 14-9)
Sections 1911 and 1912 of the 2006 IBC addresses anchorage to concrete.
DaveAtkins: 12*diameter to fully develop an anchor rod? Surely not. It takes 44 bar diameters to develop a #4 bar, and that's a deformed bar, not a smooth rod. Can you shed some light on this article you have?
Even so, 12 rod diameters seems awfully light to fully develop the rod in tension. I'd still like some clarification from DaveAtkins on the article he mentioned.
The second edition recommends an embedment length of 17dia, but gives an example of the concrete cone resistance for an embedment distance of 6" for a single rod, uncracked conditionof 19.5K for hef <= 11" and f'c=4ksi. It's based on the calculated capacity of the concrete cone. I think the 17dia reflects ACI guidelines, but am not certain.
Another publication by the AISC related to the design of headed anchor rods has formulae for the calculation of the embedded length that is approximately 12dia for A36 and 17dia for higher strength materials. In any event, the cone development is what determines the capacity.
If a threaded rod is used, then the end should be peened to prevent the nut from loosening during installation. In addition, the concrete should have sufficient strength to restrain the nut end.
I did mean headed anchor rods, and the article is "Design of Headed Anchor Bolts," by Shipp and Haninger, from the Second Quarter 1983 AISC Engineering Journal.
And StructuralEIT is correct--12 times the diameter is for A36 and A307 rods.
Thanks for the article information. You're right, it says 12d to fully develop an anchor bolt in tension.
I contend, however, that this does not comply with today's code, namely the hardest to follow mess ever pressed onto engineers, the ACI 318 Appendix D. Run through that procedure with 12d embedment, and you'll surely have less capacity than the rod's tensile capacity.
I just follow whatever the manuf. said with the design you have. They give you the axial, shear with various embedment, min spacing and min edge distance (or reduce it with shorter spacing and edge distance). If the # met your design load then you should be good.
COEngineer-
You can only do that with epoxy anchors. I don't know of a standard anchor bolt manufacturer that publishes values with tables for reductions based on spacings and edge distances. This is done with ACI Appendix D. If you only have a few anchor bolts maybe it wouldn't be a problem, but when you have a job with 100 columns and 400 anchor bolts, I imagine it can become cost prohibitive.
I have only ever used it for field fixes when the contractor mis-placed the anchor bolts.
The ASCE "Guide to Wind Loads and Anchor Bolt Design in Petrochemical Facilities" calls for a MINIMUM embedment of 12Db, but the method behind the design is to transfer the tension from the bolt into the reinforcing. I agree with everyone else...12Db is NOT enough to develop the bolt tension in plain concrete according to today's code. However, using reinforcing to help develop the bolt tension will greatly reduce your embedment depth.
Most popular on the market inserts (pre installed or post) are Dayton superior, Hilti, Meadow Burke, etc. For most of their inserts or lifters they provide the capacities and reduction factors for edge distance, spacing, embedments etc. Even if few of them are missing, you can always call them and get the information you need.
