Minimum length for what? Developing the rod in concrete? What are the edge distances, what is the concrete strength etc etc...
If you are referring to anchor rods for gravity column baseplates I typically use a 12" minimum just for OSHA erection purposes which is more than enough and generally recognized by AISC (Ref: Design Guide 1: Example 4.6) as a good lower bound on embedment.
L shape (even J shape) anchor bolts are not commonly used now (because of the pull-out possibility), in my understanding. Further, the "3" 90 degree bend at the bottom" doesn't seem long enough.
WillisV:
AB's in concrete, f'c min 3000 psi, edge distance not an issue, but AISC/ACI recommends 4" min for tension on headed bolts with reinf for distances less than shear distance. Assume A307 (fy=36 ksi)...
JID:
Do you have any references on the pull out issue?
The AB's are for a pre-eng bldg and they have spec'd 12" embedment... I've rejected these, but have told them that I would look into using AB's that short... For headed bolts, the Ld is 12 diameters (low strength bolts).
I've noticed the change for a while. The pull-out issue was particularly mentioned in an article I read not long ago(I couldn't name it right now. I'll tell if I can track out).
It is interesting to note , based on the comparison of Eq. (D-15) with Eq. (D-16) of ACI-318 2005, that the pullout strength of a hooked anchor bolt is about 1/4 of the strength of a headed acnhor bolt.
In the calculation, I used 2.5Ab (Ab=cross sectional area of an anchor bolt), which is the required minimum, to replace Abrg and used 4.5do to replace eh. Then the ratio between hooked and headed pullout strength is 0.258. Can somebody double check this observation?
can someone clear up why some choose to use App D that uses the plain concrete pullout strength, rather than accouting for the lap of anchor rods with pier steel?
Lap splice lengths are provided by ACI Chapter 12 for deformed rebars. We have used those formulas for bolts (in piers) made with threaded rods, but I'm not sure they apply to threaded or unthreaded bar stock. Is there any guidance available for splice length of bolts with rebar?
Chapter 6 of Volume II - Connections of the ASD Manual of Steel Construction (page 6-18 of the 9th ed.) has a couple of examples of anchor bolt design that calculate the total embed depth required.
