11" slab on grade - max post installed anchor depth 1

[vato]

I'm attempting to specify some epoxy anchors in an 11" thick concrete slab. My concern, one of them, is how deep to drill before the bottom of the slab will blow out, or be damaged. We won't be able to tell if it blows out or cracks. The installer seems to have a "feel" for it, but I'd like to be more confident. Maybe there's a rule of thumb out there.

Trying to spec an anchor which installs with a rotary hammer drill, anchor bolt dia 3/4".

Strongly considering using a different epoxy appropriate for a core drill to avoid blow out.

thanks for any thoughts on this....

So far simpson Mech anchors are not working as I am limited in depth to 7" for mech per code here on mech anchors. Checking out hilti.

 

[dik]

Removed... I was thinking of the post itself being embedded.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Enable]

Is HY-200 not common in your neck of the woods? It's what we exclusively use for retrofit anchorage. They also have a great design software, PROFIS (see here:

https://www.hilti.ca/content/hilti/...l-engineering/profis-engineering-suite.html),

that will aid in your detailing for future projects.

For this project, the HY-200 literature is what you want (see here:

https://www.hilti.ca/medias/sys_mas...hnical-information-ASSET-DOC-LOC-1544930.pdf)

Concrete Depth Min = Effective Embedment + 2*bit diameter

EDIT - I originally quoted a table for specific anchors (just used on previous project). I have now updated for the more generic threaded rod, which is Table 38. Note generic threaded rod and HAS are interchangeable as long as you cut a V in the base of the threaded rod

 

[canwesteng]

If you swap threaded rod for HAS, good idea to also degrease it.

 

[Enable]

canwesteng: I want to know what project you were on when that happened lol. I bet there is a real good story there

 

[racookpe1978]

Before worrying more, FIRST check the maximum effective depth for 3/4 dia Hilti epoxied-in anchor bolts.

(As I recall, they (3/4 anchor bolts) max out capacity after 5-6 inches for both vertical pull-out and shear resistacne. Hilti requires a specific cleaning ritual, specific hole diameters for their two-part epoxies, and a maximum "below-anchor bolt end" cavity, so the 11 inch depth of the concrete slab is beyond the 5-6 inch hole depth Hilti requires.

 

[Enable]

racookpe1978: No idea where you are coming up with those maximum effective depths. In my industry we regularly exceed such depths and Table 40 of the technical extract I linked to above has values for 3/4" threaded rod up to effective embedment depths of 15"

Cleaning ritual LOL never heard of it being described like that before. But yes. It is a hell of a process (to do per spec) and if we are talking vertical application, piston plugs, are required (last time I did it vertically anyways).

 

[Ingenuity]

Note generic threaded rod and HAS are interchangeable as long as you cut a V in the base of the threaded rod

I do not think the chisel-point is mandatory. If you purchase custom length anchor rods from HILTI they seldom come with chisel-points unless specifically specified at time of order.

 

[dik]

Thanks... didn't know that. I often use F1554, HDG Grade 55S1 with Hit-Hy200... I like anchors to be weldable (another personal quirk) I've not 'V'd the bottoms. I'll do that in future.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Ingenuity]

I've not 'V'd the bottoms. I'll do that in future.

It is just a 'HILTI-thing' for STOCK length anchor rods.

V-cut ends (i.e. chisel-point) is NOT mandatory for their HY-200 (or other) resins.

Just last week I purchased custom 1" dia x 36" long HILTI anchor rods, HDG, ASTM F1554, grade 105, and they are square cut.

 

[Enable]

It's not mandatory but a very, very good idea. Threaded rods set in epoxy are super easy to over torque without it. The v simply allows for excess epoxy to form a stop so it takes a hell of a lot of man force to break the bond. I would not trust anchors in the applications we use them for without such V. No test data to refer to just experience with install (...and things failing enough to say F that).

I do not think the chisel-point is mandatory. If you purchase custom length anchor rods from HILTI they seldom come with chisel-points unless specifically specified at time of order.

This must depend on the length or be a regional quirk. Any length I have ordered comes with the V base, and I have never specifically asked for it.

 

[vato]

Thanks, I was enjoying the simpson software, but from what I can tell they don't have diamond core drill bit option. Hilti does offer an epoxy anchor for a diamond bit, with a roughening step.

We are xraying the slab so theoretically, we will know where the rebar is, so we can avoid it with the core drill.

I am sharpening the pencil once more to see if a shallow(er) hole can work, but my gut is wanting a deep embed without any type of hammer drill.

Right now, a 9" hole is required for ~7" heff for the simpson epoxy anchor.

 

[Ingenuity]

The v simply allows for excess epoxy to form a stop so it takes a hell of a lot of man force to break the bond. I would not trust anchors in the applications we use them for without such V.

I am not seeing the advantage with V-end rod prep and the resulting 'epoxy stop'.

Most of the bond capacity/stresses will be taken by the upper portions of the threaded length, and the end of the threaded rod will not see significant stresses (except to engage the pullout cone for concrete failure).

Square-cut anchor rods are perfectly fine. I installed these on Monday at 8:30am with HILTI HY-200. Preloaded them to 45,000 lbf (70% of yield) at 1:30pm, same day. We will be re-checking preload in 7 days.

V-ends (chisel-point) are used with capsule-type anchors to break the glass and aid in mixing the resin.

 

[Enable]

Disagree. How much it helps is a function of length. Longer the shaft the more will be taken above the V. But for the range we use (6-12") it matters quite a bit and our technical consultant from Hilti has affirmed as much.

I don't doubt for the length of rods in your picture though it would be relatively unimportant.

EDIT - See Hilti Guide here:

https://www.buildsite.com/pdf/hilti/Hilti-2011-Anchor-Fastening-Technical-Guide-B25981.pdf

Threaded Rods shall be furnished with chamfered ends so that either end will
accept a nut and washer. Alternatively, anchor rods shall be furnished with a 45 degree chisel point on one end to allow
for easy insertion into the adhesive-filled hole

So the way I read the guide is that Ingenuity may be correct in that it is not required. Still contend it helps at smaller lengths.

 

[Ingenuity]

From Portland Bolt: Link

 

[Ingenuity]

I don't want to come across as argumentative (after all, we are engineer's here not lawyer's) but I checked in with my HILTI rep (a company that I have 25+ years of extreme loyalty with tools, components and equipment etc) and he said "...it distinguishes HILTI rods from the competition", except when capsule-based anchors are used and chisel-points are required.

Enable: it may be a Hilti Canada thing

Sorry OP - for hijacking your post...back to regular programming

 

[Enable]

I appreciate the reference and view point (I am inclined to believe you are generally correct especially since the Hilti guide seems to permit chamfered ends as a substitute). However, based on my personal tightening experience I cannot say it does not matter....I've just seen it fail side by side when a v shaped end does not. Though it does seem like a trivial distinction at some length (you think L_trivial = 0, I think slightly more lol).

 

[dik]

It kinda makes sense, having the chisle... going through the epoxy in place and offering greater resistance to torque for smaller lengths.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik