"k" values for Bolt Thru concrete anchor??
"k" values for Bolt Thru concrete anchor??
(OP)
I'm analyzing a steel bolt thru anchor that was installed thru a hardened reinforced concrete slab. The slab was core drilled, and then the anchor was pushed thru the hole. On the backside is a 3"x3"x1/2" back plate. The anchor is loaded in pure tension.
I'm trying to determine the concrete breakout strength of an anchor in tension in accordance with ACI 318 (2002) D.5.2. The capacity of the anchor is highly dependent on the "k" coefficient found in equation D-7; the basic concrete breakout strength equation. I'm having trouble determining an appropriate "k" value for a thru-bolt anchor. I would consider the thru-bolt anchor post-installed, however I believe it will act more like a cast-in anchor. The code refers to post-installed anchors as expansion and undercut, and has a reduced "k" value compared to cast-in. The code also allows for "k" values higher than 17 as permitted for post-installed.
Does anyone know the "k" value for a bolt-thru anchor? Thanks!
I'm trying to determine the concrete breakout strength of an anchor in tension in accordance with ACI 318 (2002) D.5.2. The capacity of the anchor is highly dependent on the "k" coefficient found in equation D-7; the basic concrete breakout strength equation. I'm having trouble determining an appropriate "k" value for a thru-bolt anchor. I would consider the thru-bolt anchor post-installed, however I believe it will act more like a cast-in anchor. The code refers to post-installed anchors as expansion and undercut, and has a reduced "k" value compared to cast-in. The code also allows for "k" values higher than 17 as permitted for post-installed.
Does anyone know the "k" value for a bolt-thru anchor? Thanks!





RE: "k" values for Bolt Thru concrete anchor??
Epoxy bolts in concrete do not fail in the same manner as expansion bolts or embedded bolts. They fail by shear interface failure between the epoxy and concrete, so a pullout cone is not developed.
RE: "k" values for Bolt Thru concrete anchor??
The plate does not fit throught the hole. The plate is attached at the underside of the concrete deck. The diameter of the core drilled hole is approx. 1/16" greater than the diameter of the bolt.
I'm not talking about adhesive anchors, however adhesive anchors can fail with a pullout cone. It all depends on the material properties and configurations.
Thanks!
RE: "k" values for Bolt Thru concrete anchor??
RE: "k" values for Bolt Thru concrete anchor??
RE: "k" values for Bolt Thru concrete anchor??
RE: "k" values for Bolt Thru concrete anchor??
StructuralEIT - Thanks for the response! Do you know of any references that state the "k" values are proportionate to micro-cracking? From my understanding the "k" values are determined from testing.
RE: "k" values for Bolt Thru concrete anchor??
They are determined for post-installed anchors (were determined for cast-in) anchors by testing, but, again, the variable that this is trying to capture is the micro-cracking around the anchor.
RE: "k" values for Bolt Thru concrete anchor??
RE: "k" values for Bolt Thru concrete anchor??
RE: "k" values for Bolt Thru concrete anchor??
ekhaw, I believe you have answered my question!!! Sometimes it might help to read the entire chapter. Thru bolts are not governed by ACI 318 Appendix D.
I have no knowledge of provisions for the design of thru bolt anchors other than punching shear.